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Guidelines for Planning and Designing HydroDevelopments Vol. 4 Small Scale 1989
HYD 069 Civil Engineering Guidelines for Planning and Designing Hydroelectric Developments Volume4 Srnall Scale Hydro Division I. Planning Division II. Design Division Ill. Construction Civil Engineering Guidelines for Planning and Designing Hydroelectric Developments Volume4 Small Scale Hydro Division I. Planning Division II. Design Division Ill. Construction Approved for publication by the Energy Division of the American Society of Civil Engineers Published by the American Society of Civil Engineef'S 345 East 47th Street New York, New York 10017-2398 ~}I 'J ABSTRACT Civil Engineering Guidelines for Planning and Designing Hydroelectric Develop· ments was prepared under the auspices of the Hydropower Committee of the ASCE Energy Div1sion. The Guidelines is divided into five volumes. The first volume con- cerns the planning and desigmng of dams and related toptcs, and environmental tssues. Volume 2 discusses the design of waterways including such elements as intakes, tunnels and shafts. penstocks, surge tanks, and gates. Volume 3 covers the design of powerhouses and related topics. While the first three volumes deal with conventional hydroelectric proJects, the fourth volume is concerned with the plan- mng, designing, and construction of small-scale hydroelectric projects. The last vol· ume provides information on the planning, designing, operation and maintenance of elements concerned w1th pumped storage. This volume ends with a discussion on different aspects of tidal power including design and construction considerations. Thus, the Gwdelines provides comprehensive coverage and the necessary infor- mation on the type and depth of studies needed for developing and designing hydroelectnc projects. The matenal presented in this publication has been prepared in accordance with generally recognized engineering principles and practices and is for general infor· mation only. This information should not be used without first securing competent advice with respect to its suitability for any general or specific application. The contents of this publication are not intended to be and should not be construed to be a standard of the American Society of Civil Engineers (ASCE) or the Electric Power Research Institute (EPAI) and are not intended for use as a reference in pur- chase specifications, contracts, regulations. statutes, or any other legal document. No reference made in this publication to any specific method, product, process, or service cons1itutes or implies an endorsement, recommendation, or W8mlf1ty thereof by ASCE or EPAI, sponsors of the wont. ASCE and EPAI make no representation or warranty of any kind, whether expressed or 1mplied, concerning the accuracy, completeness, suitability, or utility of any infor· mation. apparatus, product, or process discussed in this publication, and assume no liability therefor. Anyone using this information assumes all liability arising from such use, including but not limited to infringement of any patent or patents. Copyright © 1989 by the American Society of Civil Engineers. All Rights Reserved. Library of Congress Catalog Card No. 89-045882 Series ISBN 0·87262-725-X Volume ISBN 0-87262-729·2 Manufactured in the United States of America. FOREWORD Civil Engineering Guidelines for Planning and Designing Hydroelectric Developments was prepared by the Hydropower Committee of the ASCE Energy Division. The committee's work on the Guidelines received substantial financial support from the Electric Power Research Institute (EPRI), without which the preparation of these Guidelines would have been impossible. The Guidelines began in response to the formulation of1he purpose of the Hydropower Committee at the meeting in Houston, Texas, in October 1983, when the committee was reactivated. The purpose of the committee as restated in 1983, was to "investigate and disseminate information on all phases of hydro- electric power." At the time there was a noticeable gap between the state of the art and the literature. There was a need for a comprehensive document that pulled together the widely recognized hydro-related design information using appropriate text and references. Because of the small initial membership of the Hydropower Committee, the original intent was merely a civil engineering hydroelectric design symposium involving publication of state-of-the-an papers. Additional papers would be added later to close apparent information gaps. However, as more members joined the committee, the objective and scope of the Guidelines grew. Membership reached almost 40- the largest ever for the Hydropower Committee and among the highest of all technical committees in the Energy Division. In early 1986, the outline of the Guidelines was fmalized, and the work of writing a completely new document began in earnest. The objective of the Guidelines is to provide material that is useful to an engineer having 5 to 10 years experience and basic knowledge of the design of hydroelectric developments. The Guidelines provide comprehensive coverage and the necessary information on the type and depth of studies needed for developing and designing a successful hydroelectric project. The Guidelines emphasizes the planning and design of the "powertrain," which includes the intakes, power conduits, powerhouses, and associated elements. The intent was to include the technology and practices that have developed during the past 25 years, but also to recognize precedent designs of earlier periods, especially that after World War II. The text is arranged so that engineers can add their own notes in the margins. QuarkXPress electronic publishing software was used to lay out all of the pages of the Guidelines. Many of the authors' original drafts were printed using IBM-compatible computers, and the files were converted to a Macintosh for- mat. Equations were created using a Macintosh software program. The Hydropower Committee intends to publish a revision to the Guidelines early in 1991. To this end, a form is enclosed that allows readers to order this revision or to offer comments, corrections, or additions. Recognition is due to the Hydropower Committee members, especially those who remained active con- tributors until completion of the Guidelines and dedicated many hours of their personal time to this undertaking. Recognition is also due to the organizations, both public and private, that supported the par- ticipation of the committee members, allowing them to attend meetings and providing the office assis- tance required for the chairmen and control members to administer related committee activities. James Birk and Charles Sullivan of EPRI were instrumental in the successful completion of the work by recognizing the committee's capability to develop the Guidelines and by securing the necessary funding ASCE/EPRI Guides 1989 FOREWORD-Continued Douglas Morris, EPRI Project Manager, monitored and directed the EPRI-related activities of the com- mittee and contributed significantly in the review of the Guidelines. Philip M. Botch, who served as Energy Division Contact Member of the committee until his death in 1986, provided substantial contributions and suppon for the project. As the new contact member and Executive Committee Chairman during 1984, Don Matchett continued to provide support for the Hydropower Committee's work and for the Guidelines. Special recognition goes to Tom Logan, who under contract with EPRI, spearheaded preparation of the Guidelines with great devotion. By organizing meetings, communicating directly with the authors, and arranging for the review, editing, and typesetting of the Guidelines, Tom contributed greatly to the successful completion of this monumental project. Joe Carriero assisted Tom in organizing the material and provided valuable expertise in editing and format- ting the Guidelines. Finally, special gratitude is due to Arvids Zagars. Without his dedicated leadership, the Guidelines would not have been written. Arvids established the initial concept and provided the direction that guided the authors. He served as committee chairman for the entire period during which the Guidelines were written. In addition, he authored several major chapters and provided valuable input to many other chapters on which his name does not appear as a contributor. Respectfully submitted, ASCE Hydropower Committee Edgar T. Moore, P.E. Hydropower Committee Chairman 1989 ASCEJEPRI Guides 1989 ASCE ENERGY DMSION EXECUTIVE COMMITTEE CONTACT MEMBERS Donald Matchett. P.E., Stone & Webster Engineering Corp., Denver, Colorado Philip M. Botch, P.E., P.M. Botch and Associates, Bellevue, Washington ASCE CONTROL GROUP MEMBERS, 1984-1988 Arvids Zagars, P.E., Chainnan, ASCE Hydropower Development Committee, Hana Engineering Co., Chicago. Illinois R.A. Corso, P.E., Federal Energy Regulatory Committee, WashingtOn, D.C. Garith Grinnell, P.E .• Stone and Webster Engineering Co., Denver, Colorado Edgar Moore, P.E., Harza Engineering Co., Chicago, lliinois Sydney Steinborn, P.E., Steinborn Associates, Seattle, Washington EPRI PROGRAM MANAGER Douglas I. Morris, EPRI, Palo Alto, California EDITOR AND TECHNICAL COORDINATOR Thomas H. Logan, P.E., Consultant, 1310 Wadsworth Blvd., Suite 100, Lakewood, Colorado 80215 PUBLISlllNG COORDINATOR Joe Carriero, P.E., Consultant, 2240 Harlan Street, Denver, Colorado 80214 TYPESETTERS John Cruise and A. Celeste Velasquez, 330 East lOth Avenue, 1#810, Denver, Colorado 80203 SMALL-SCALE HYDROPOWER SUBCOMMIITEE MEMBERS Thomas G. Gebhard, Jr., Chairman, Gebhard Engineers, Austin, Texas Ashok K. Rajpal, Vice Chairman, Mead and Hunt, Inc .• Madison, Wisconsin Charles E. Bohac, Tennessee Valley Authority, Chattanooga, Tennessee Essam A. Farag, Tile SNC Group, Montreal, Quebec, Canada Garith Grinnell, Stone and Webster Engineering Corp., Denver, Colorado Richard T. Hunt, Concord, New Hampshire Ronald F. Ott. Ott Water Engineers, Bellevue, Washington Anand Prakash, Dames and Moore, Golden, Colorado Ray Toney, Ray Toney & Associates, Redding, California ORGANIZATIONS THAT PROVIDED CONTINUOUS SUPPORT FOR COMMITTEE MEMBER PARTICIPATION IN PREPARATION OF THE GUIDELINES Harza Engineering Company (Support for all administrative activities of the Committee Chairman) Chicago Bridge and Iron Company Dames and Moore Electric Power Research Institute Gebhard Engineers Mead and Hunt. Inc. New York Power Authority Northeast Utilities Service Company Pacific Gas and Electric Company Steinborn Associates Stone and Webster Engineering Bureau of Reclamation U.S. Army Corps of Engineers Federal Energy Regulatory Commission Tennessee Valley Authority Ott Water Engineers OTHER PARTICIPATING ORGANIZATIONS R.W. Beck Black and Veatch Duke Power Company Ebasco Services, Inc. Gilbert Commonwealth Richard Hunt and Associates Southern Company Services The SNC Group Ray Toney and Associates University of Minnesota, St Anthony Falls Hydraulic Laboratory University of Wisconsin-Milwaukee CIVIL ENGINEERING GUIDELINES FOR PLANNING AND DESIGNING HYDROELECTRIC DEVELOPMENTS VOLUME 1. PLANNING, DESIGN OF DAMS AND RELATED TOPICS, AND ENVIRONMENTAL CONVENTIONAL HYDRO DIVISION I. PLANNING O.aprer 1. Development of the Study Plan O.apcer 2. Laad-Resoun:e Analysis O!aprer 3. Hydrologic and Geologic Studies Qaprer 4. Estimating Power Pocential O.apcer 5. Power Plant Sizing O.aprer 6. Power Plant Cost Estimates O!apter 7. Ecooomic Evaluation of Hydropower Projects O!apter 8. Environmental Impacts and Pertinent Legislation O!apcer 9. Glossuy of Hydropower Planning Tenns DIVISION II. DESIGN PART A. DAMS A..'ID RELATED TOPICS O!apter I. Dams O!apter 2. Spillways O!apter3. Outlets *O!apter 4. Diversions O!aprer S. ReservoiiS Qapcer 6. Geologic Investigations PART D. ENVIRONMENTAL O!apcer 1. Environmental Issues and Mitigative Approaches VOLUME 1. WATERWAYS CONVENTIONAL HYDRO DIVISION II. DESIGN PART B. WATERWAYS O!apter I. Intakes Qaprer 2. Power Canals and Tailraces Qaprer 3. Tunnels and Sltal\s O.aprer 4. Pensaocb O!ap«er S. Steady Flow in Oosed Conduits O!apcer 6. Transiertts and Saqe Tanis O!apcer 7. Hydraulic Models O.aprer 8. Gates and Valves VOLUME 3. POWERHOUSES AND RELATED TOPICS CONVENTIONAL HYDRO DIVISION II. DESIGN PART C. POWERHOUSES AND RELATED TOPICS O!aprer 1. Powemouses-Surface and Underground Olapcer 2. Hydraulic Turbines and Related Topics Qaprer 3. Electrical Engineering O!apter 4. Transmission Lines and Switcbyuds *Not included in 1989 edition. VOLUME 4. SMALL-SCALE HYDRO DIVISION I. PLANNING O!aprer l. Small-Scale Hydropower Perspectives Qaprer 2. Development of Level and Scope of Study Plan Qaprer 3. Site Evaluation Qaprer 4. Hydrologic Data O!apter 5. Estimating Plant Capacity and Power Output Chapcer6. Power System Use and CCIUlection Requirements Chapcer 7. Operation and Maintenance O!apter 8. Environmental Issues O!apter 9. Institutional Issues O!apter 10. Project Schedule Qaprer 11. Cost Estimates Chapter 12. Ecooomic Analysis DIVISION IL DESIGN Qaprer l. Storage, Diversion, and Appurtenant Structures O!apter 2. Watetways Chapter 3. Power Plants O!apter 4. Substation and Transmission Lines DIVISION IlL CONSTRUCTION *o.apc.er l. Construction Contracts O.aprer 2. Acceptanc:e Tests VOLUME 5. PUMPED STORAGE AND TIDAL POWER PUMPED STORAGE DIVISION L PLANNING Qaprer 1. General Concepts Qaprer 2. Environmental Issues and Public Acceptance Qaprer 3. Planning DIVISION lL DESIGN PART A. RESERVOIRS Qaprer 1. Reservoirs PART 8. WATERWAYS O!apter I. Inlates and Outlets • O!apter 2. Tunnels, Shafts, and Penstocks *O!apter 3. Hydraulics Qapter 4. Transients PART C. POWERHOUSES AND RELATED TOPICS Qaprer 1. Powerllouses Chapcer 2. Pumpll'urbines and Plant Operation DMSION IlL OPERATION AND MAINTENANCE Chapcer 1. Operation aod Maintenaoce TIDAL POWER Chapcer 1. Introduction Chapcer 2. Buies of Tidal Power Chapcer 3. Preliminuy Design Considerations O!apter 4. CooSlnlctioo Considerations O!apter S. Project Description O!apcer 6. Significant Tidal Ranges NOTICE TO READERS OF THE GUIDELINES The Hydropower Committee of the Energy Engineering Division of ASCE has prepared these Guidelines in a fonnat that allows easy revision and updating. It is the intention of the committee to provide a revi- sion, in January 1991. The cost of this revision will be that of reproduction and mailing. If you wish to make corrections or additions, or wish to receive the 1991 revision, please fill out the fonn below and return it to: ASCE EY-DIVISION, HYDROPOWER COMMITIEE Attention: E.T. Moore, Jr. Room 1700 150 South Wacker Drive Chicago, illinois 60606 0 I wish to receive the 1991 revision to the Guidelines. Name ------------------------------------------- Company --------------------------------------- Mailing Address: Street--------------------------- City---------------- State _________________ Zip ____ _ Tel: ( ) ~---~-------------------------- 0 My comments, corrections, or additions are attached. GLOSSARY OF HYDROPOWER TERMS-1989* • This glossary was assembled and edited by Tom Logan and Joe Carriero from nine of the better glos- saries available (USBR, COE, BPA, ASCE, ASME, IEEE, EEl, AWWA, and ANL). It is not "approved" by the Hydropower Development Committee for use because it has not been distributed for approval at the time of the publication of these Guidellnes. ASCE/EPRI Guides 1989 GLOSSARY OF HYDROPOWER TERMS Adverse water conditions. Water conditions that limit the production of hydroelectric power, either because of low water supply or reduced gross head or both. Sometimes called critical water conditions. Afterbay. See Tailrace. Alternating Current (ac). An electric current that peri- odically reverses its direction of flow, as contrasted with Direct current. which travels in only one direction. Anadromous tish. Fish, such as salmon, that migrate up rivers from the sea to spawn in fresh water. Annual costs. As distinguished from Capital costs, those expenses associated with the yearly operation of a hydropower facility, including maintenance, replace- ment, administration, insurance, taxes, lease payments, debt service, etc. Appraisal study. A preliminary feasibility study made to determine whether a detailed Feasibility study is warranted. Also called a Reconnaissance study. Armature. That part of an electric rotating machine that includes the main current-carrying winding in which the electromotive force produced by magnetic flux rotation is induced; it may be rotating or stationary. Availability. The percentage of time a plant is available for power production. Average annual flow. The rate at which water flows through a conduit or channel, determined by averaging daily measurements of this rate over the course of a year; normally expressed in cubic feet per second (ft3/s) or cubic meters per second (m3/s). Availability. Average availability (also Hydrologic availability). The ratio of the average capacity of a hydroelectric plant in the peak demand months to its rated capacity. This ratio accounts for variations in streamflow and head. Mechanical availability. The ratio of the number of days in total period minus days out of service due to maintenance and forced outages, to the number of days in the total period. (See also Outages). Average load. The hypothetical constant load over a specified time period that would produce the same ener- gy as the actual load would produce for the same period. G-1 Average water conditions. Precipitation and runoff conditions which provide water for hydroelectric power development approximating the average amount and distribution available over a long time period, usually the period of record. Avoided cost. The estimated sum of money that would have been spent on the lowest cost alternative generat- ing plant that would be used if the small hydro project did not exist; used in setting power prices. Axial hydraulic thrust. In single-stage and multistage pumps, the summation of unbalanced impeller forces acting in the axial direction. Backup. Reserve generating capacity of a power system. Backwater. Water level controlled by either a down- stream reservoir, a channel restriction, or a stream con- fluence that affects the tailwater level of an upstream plant. Band. The shroud ring at the bottom of a Francis runner to which the blades are attached. Banki turbine. (See Crossflow turbine.) Base load. The minimum electrical system load over a given period of time. Beneftt-cost ratio (B/C). The ratio of the present value of the benefit stream to the present value of the project cost stream used in economic analysis. Benefits (Economic). The increase in economic value produced by a project, typically represented as a time stream of value produced by the generation of hydro- electric power. Bifurcation. Division into two branches. Black start. The startup of a power plant without an external electrical supply. Blade. That part of a rotating fan or propeller arm that has an airfoil shape. Block loading. A generating plant is said to be block loaded when its output is increased or decreased in defi- nite steps without regard to following a particular load shape. A generating plant carries a block load when its output is maintained at a fixed level for an extended period of time. ASCE/EPRI Guides 1989 Bottom deck. Lower part of the headcover of a hydraulic turbine. British thermal unit (Btu). The quantity of heat energy required to raise the temperature of 1 pound of water 1 degree Fahrenheit, at sea level. Bucket. A cup on the rim of a Pelton wheel against which water impinges. Bulb turbine. An axial flow turbine situated in a straight-through water passage. The generator is enclosed in a streamlined watertight bulb located in the water passageway on either the upstream or the down- stream side of the runner. Bulb unit-turbine generator. A unit consisting of a horizontal shaft hydraulic turbine and close coupled generator that are ooth enclosed in a single steel water- tight bulb located directly in the water passage. Bulkhead gate. A gate installed at the entrance of a fluid passage and used to dewater the passage for inspection and maintenance. Almost always opened or closed under balanced pressure. Bus. An electrical conductor that serves as a common connection for two or more electrical circuits. A bus may be in the form of rigid bars, either circular or rect- angular in cross section, or in the form of stranded -con- ductor overhead cables held under tension. Busbar. An electricconductor in the form of rigid bars, located in switchyards or power plants, serving as a common connection for two or more electrical circuits. Capability. The maximum load which a generator, tur- bine, transmission circuit, apparatus, station, or system can supply under specified conditions for a given time interval, without exceeding approved limits of tempera- ture and stress. Peaking capability. The maximum peak load that can be supplied by a generating unit, powerplant, or power system in a stated time period. It may be the maximum instantaneous load or the maximum aver- age load over a designated interval of time. Sometimes called peaking capability. Capacity. The load for which a generator, turbine, trans- former, transmission circuit. apparatus, station or system is rated. Capacity is also used synonymously with capa- bility. For definitions pertinent to the capacity of a reser- voir to store water, see Reservoir storage capacity. Assured system capacity. The dependable capacity of system facilities available for serving system load ASCE/EPRI Guides 1989 after allowance for required reserve capacity, includ- ing the effect of emergency interchange agreements and finn power agreements with other systems. Dependable capacity. The load-carrying ability of a station or system under adverse conditions for the time interval and period specified when related to the characteristics of the load to be supplied. The depend- able capacity of a system includes net firm power purchases. Equivalent thermal capacity. The amount of thermal generating capacity that would carry the same amount of system peak load as could be carried by a given hydroelectric plant. Hydraulic capacity. The maximum flow which a hydroelectric plant can utilize for energy. Installed capacity. The sum of the capacities in a powerplant or power system, as shown by the name- plate ratings of similar kinds of apparatus, such as generating units, turbines, or other equipment Overload capacity. The maximum load that a gener- ating unit or other device can carry for a specified period of time under specified conditions when oper- ating beyond its normal rating but within the limits of the manufacturer's guarantee, or, in the case of expi- ration of the guarantee, within safe limits as deter- mined by the owner. Pealcing capacity. The maximum peak load that can be supplied by a generating unit, powerplant, or power system in a stated time period. It may be the maximum instantaneous load or the maximum aver- age load over a designated interval of time. Sometimes called peaking capability. Rated capacity. The electrical load for which a gener- ator, turbine. transformer, transmission circuit. electri· cal apparatus, powerplant, or power system is rated. Resent generating capacity. Extra generating capac- ity available to meet unanticipated demands for power or to generate power in the event of loss of generation resulting from scheduled or unscheduled outages of regularly used generating capacity. Sustained peaking capacity. Capacity that is support- ed by a sufficient amount of energy to permit it to be fully usable in meeting system loads. Capacitor. A dielectric device that momentarily absorbs and stores electrical energy. Capacity factor. The ratio of ·the energy that a plant produces to the energy that would be produced if it were operated at full Capacity throughout a given period, usually a year. Sometimes called the Plant factor. Capacity interchange. In power pooling, transactions resulting from the assignment by participating utilities of reserve or excess generating capacity for common use. G-2 Capacity value. That portion of the at-site or at-market value of electric power which is assigned to capacity. Capital cost. Costs associated with the development and construction of a hydropower facility, including land, structures, improvements, power generation and transmission equipment, engineering, administrative fees, legal fees, financing costs, and contingencies. Capitalize. To convert into an equivalent capital sum. To compute, appraise, or estimate the present value of. Capital recovery factor. A factor used to convert a one-time investment into an equivalent annual cost at a given interest rate for a specified period of time. Cascade. An arrangement of separate devices so that they multiply the effect of each individual device. Cash flow. The net profits of a business plus the charges of the accounting period for depreciation, depletion, amortization, and extraordinary charges to reserves not paid in case. Cavitation. The formation of voids within a body of moving liquid (or around a body moving in a liquid) when the local pressure is lower than the vapor pressure, and the particles of liquid fail to adhere to the bound- aries of the passageway. These voids fill with vapor and then collapse, causing pitting of metal on turbine blades. Central station service. Electric service supplied from an electrical system rather than by self-generation. Charge/discharge ratio. The ratio of the average pumping load on a pump/turbine unit to its rated gener- ating output Circuit breaker. Any switching device that is capable of closing or interrupting an electrical circuit. Civil works. All heavy construction work. associated with dams, tunnels, canals, conduits, penstocks, power- house structures, access roads, bridges, and site improvements. Cogeneration. The use of waste heat to drive turbine generators for electricity generation. Also, the use of low-pressure exhaust steam from an electric generating plant to heat an industrial process or a space. Coincident demand. Any demand that occurs simulta- neously with any other demand; also the sum of any set of coincident demands. 0-3 Cold reserve. Reserve generating capacity available for service but not in operation. Combined cycle. An electric power plant consisting of a series of combustion turbines with heat extractors on their exhausts. Combustion turbine. An electric power plant consist- ing of natural gas or distillate oil-fired jet engines con- nected to a generator. Conduit. A pipeline, tunnel, or canal used for the con- veyance of water. Conservatory storage. That portion of the water stored in a reservoir that is impounded for later use. The term "conservation storage" is synonymous with active stor- age. Conservation storage is the portion of a reservoir's live storage that is normally conserved for beneficial use at-site or downstream. but does not include any live storage space reserved exclusively for flood control. Costs (economic). The stream of value required to pro- duce the project output. In hydro projects this is often limited to the management and construction cost required to develop the power plant, and the administra- tion, operations, maintenance, and replacement costs required to keep the power plant in service. Critical period. The multiple-month period when the limitation of hydroelectric power supply due to the shortage of available water is most critical with respect to system load requirements, as determined from an analysis of the historical streamflow record. The reser- voir begins the critical period full; the available storage is fully drafted at one point during the period; and the critical period ends when the storage has completely refilled. Critical speed. The angular speed at which a rotating shaft becomes dynamically unstable with large lateral amplitudes, due to resonance with natural frequencies of lateral vibration of the shaft. Critical streamflow. The amount of streamflow avail- able for hydroelectric power generation during the most adverse streamflow period. See also Streamflow. Critical water conditions. Water conditions limiting the production of hydroelectric power, either because of low water supply or reduced gross head or both. Also sometimes called adverse water conditions. Crossflow turbine. A hydraulic machine that converts hydraulic energy to mechanical energy by allowing ASCE/EPRI Guides 1988 water to flow in one side, then out the other side of a cylindrical turbine runner. Crown. The top portion of a Francis runner to which the blades are attached. Cumulative impact study. A study of the net environ- mental impact of two or more hydro projects on the same river system. Current (electric). The rate of flow of electric charge through a conductor or circuit. Measured in amperes. Cycle efficiency. The ratio of the generating output of a pumped-storage plant to its pumping energy input. Includes motor, pump, turbine, and generator efficiency losses and water conduit head losses. Cycling. Power plant operation to meet the intermediate portion of the load (9 to 14 hours per day). ..._. Dam. A structure for impounding water. Dead storage. The portion of a storage basin or reser- voir that cannot be used for temporary water storage. Debt service. Principal and interest payment on the debt used to finance the project. Demand. The rate at which electric energy is delivered to or by a system or to a piece of equipment. Demand factor. The ratio of the maximum demand of a system, or part of a system, to the total connected load of the system, or part of the system, under considera- tion. Dependable capacity. The expected load-carrying abil- Direct current (de). Electricity that flows continuously in one direction, as contrasted with Alternating current. Disk friction loss. Energy loss in a machine due to hydraulic friction between the liquid and the rotating faces of the runner. Discharge. The rate of water flow through, over, or around water control facilities. The rate of flow is mea- sured by stream gage or calculated from predetermined rating tables. The term may be applied to the rate of flow from each individual source (such as a particular turbine) or to the algebraic summation from all individu- al sources (which would be the total rate of flow). Total discharge is synonymous with outflow. Rated discharge. Turbine discharge at rated head, with wicket gates in fully open position. Discharge ring. A turbine component located below the runner and stay ring. It provides the foundation for the machine, and lower bearing surface for the wicket gates. Discount rate. Interest rate used in the economic eval- uation of a project to account for the time value of money. Dispatching. The operating control of generating units, transmission lines, and other facilities, including assign- ing of generator outputs as needed, controlling mainte- nance and switching operations, and scheduling energy transactions with other utilities. Distributor. Components (spiral case, headcover, stay ring, and discharge ring) of a turbine whose purpose is to contain and guide the water from inlet to exit ity of a hydropower plant under specified conditions. ~Diversion structure. A structure built to divert or alter Deriaz turbine. A diagonal-flow turbine with a pro- peller runner whose blades are adjustable and the axis of the blades is at an angle with the axis of the shaft. Design head. The Head at which the Runner of a tur- bine is designed to provide the highest efficiency. Measured in feet or meters. Dewatering. Removing or draining water from an enclosure or a structure. Diffuser. A duct, chamber, or section in which a high- velocity, low-pressure stream of fluid (usually air) is converted into a low-velocity, high-pressure flow. ASCE/EPRI Guides 1989 the course of a stream of water. Diversity. The difference among individual electric loads resulting from the fact that the maximum demands of customers do not all occur at the same time. Diversity factor. Ratio of the sum of the individual maximum demands of the various subdivisions of a sys- tem, or pan of a system, to the maximum demand of the whole system, or part, under consideration. Draft. The withdrawal of water from a reservoir. Draft tube. A conduit that canies water from a reaction turbine runner or crossflow turbine runner to the tailrace. Designed to maximize head utilization by the turbine. G-4 Drag. In hydraulics, those forces that oppose motion due to shear stress or the object's form. Drainage area. The area of land draining to a stream or power plant. Sometimes called catchment area. Drawdown. The distance that the water surface eleva- tion of a storage reservoir is lowered as a result of the withdrawal of water to meet some project purpose (i.e., power generation, flood control space, irrigation demand, etc.). Duration curve. A curve of quantities plotted in descending sequential order of magnitude against time intervals for a specified period. The coordinates may be absolute quantities or percentages Eddy. The vonex motion of a fluid. Aow is usually opposite the main flow direction. Efficiency. The ratio of energy developed by a machine to the energy supplied to it. Efficiency, turbine. Accounts for hydraulic friction and eddy losses through the spiral case, stay ring, wicket gates, runner, and draft tube of a turbine, as well as the kinetic energy of the water at draft tube exit that has not been converted into useful work by the turbine. Efficiency, mechanical. Ratio of the power available at the shaft to that exened on the runner for a turbine (vice versa for a pump). It accounts for bearing and disk fric- tion, and the drag on the runner in the clearance spaces. Efficiency, overall. Accounts for all the system efficien- cies, hydraulic, turbine, generator, and transformer. Efficiency, volumetric. The ratio of the quantity of water that produces useful work to the total quantity of water supplied to a turbine (vice versa for a pump). It accounts for the loss of efficiency due to water leaking past the runner through clearance spaces without doing any useful work or being pumped. Electric power system. Physically connected electric generating, transmission, and distribution facilities oper- ated as a unit under one control. Encroachment. The reduction in generating head at a hydroelectric project caused by a rise in tailwater eleva- tion resulting from the backwater effects of a down- stream reservoir. G-5 Energy. That which does or is capable of doing work. It is measured in terms of the work it is capable of doing; electric energy is usually measured in kilowatt-hours. Average annual energy. The average amount of ener- gy generated by a hydroelectric project or system over the period of record or representative period of record. Dump energy. Energy generated in hydroelectric plants by water that cannot be stored or conserved and which energy is in excess of the needs of the electric system producing the energy. Firm energy. Electric energy which is intended to have assured availability to the customer to meet any or all agreed upon ponion of his load requirements. Fuel displacement energy. Electric energy generated at a hydroelectric plant as a substitute for energy which would otherwise have been generated by a thermal-electric plant Nonjirm energy. Electric energy having limited or no assured availability. Off-peak energy. Electric energy supplied during periods of relatively low system demands. On-peak energy. Electric energy supplied during periods of relatively high system demands. Primary energy. Hydroelectric energy which is avail- able from continuous power. Primary energy is finn hydroelectric energy. Pumping energy. The energy required to pump water from the lower reservoir to the upper reservoir of a pumped-storage project. Secondary energy. All hydroelectric energy other than primary energy. Secondary energy is generally mark.eted as non-finn energy. Energy value. That pan of the market value of electric production assigned to energy generation. Erection bay area. The pan of a powerhouse that pro- vides laydown space for assembly and disassembly of the turbine and generator. It is used during construction and for major maintenance operations. Sometimes called assembly or service bay. Erosion. Surface destruction of a material by the abra- sive or the corrosive action of a moving fluid. Often accelerated by solid particles in suspension. Escalation. The estimated increase in costs or revenues over a future period of years, usually expressed as or derived from an annual percentage rate. Exciter. An electrical device that supplies direct excita- tion to the generator field during startup of the unit. It may be a rotating shaft-mounted type, or a static rectifi- er type. ASCE/EPRI Guides 1989 Exemption. Special rules that pennit FERC to waive the requirement that a project be licensed under the Federal Power Act if it meets cenain capacity, project type, land ownership, and environmental criteria. Exports. Electric power which is transferred from a given power system to another (usually adjacent) power system. Expon power must be included in the given power system's loads. Factor. Availability factor. The ratio of the time a machine or equipment is ready for or in service to the total time interval under consideration Capacity factor. The ratio of the average load on a machine or equipment for the period of time consid- ered, to its capacity rating. Hydrologic availability (also average availability). The ratio of the average capacity of a hydroelectric plant in the peak demand months to its rated capacity. This ratio accounts for variations in streamflow and head. Load factor. The ratio of the average load over a des- ignated period to the peak-load occurring in that peri- od. Plant factor. The ratio of the average load on the plant for the period of time considered to the aggre- gate rating of all the generating equipment installed in the plant. Power Factor. The ratio of kilowatts to kilovolt- amperes, which is indicative of a generator's ability to deliver reactive power in addition to real power (kilowatts). Feasibility study. An investigation perfonned to fonnu- late a hydropower project and definitely assess its desir- ability for implementation. · Federal Energy Regulatory Commission (FERC). The agency of the Department of Energy that licenses non-federal hydropower projects and regulates interstate transfer of electric energy. Fonnerly the Federal Power Commission (FPC). Federal register. A daily Federal government publica- tion containing all new Federal regulations, proposed regulations, adminsitrative notices, and other docu- ments. Available by subscription from the General Services Administration. Finite element method. A method for determining the behavior of a structure from a knowledge of the behav- ior, under load, of its components. In this method a structural system is considered an assembly of a finite number of finite-size components, or elements. These are assumed to be connected to each other only at dis- ASCE/EPRI Guides 1989 crete points called nodes. From the characteristics of the elements, such as their stiffness or flexibility, the charac- teristics of the whole system can be derived. Thus, the internal stresses and strains throughout can be computed, and both static and dynamic behavior can be predicted. Firm capacity. See Dependable capacity. Firm energy. The energy generating ability of a hydropower plant in a specified time period and under adverse hydrologic conditions. Fish ladder. An anificial waterway composed of a series of stepped pools allowing fish to ascend a vertical gradient, usually built at one end of a dam. Fishscreen. Barrier installed to divert the downstream migrating fish into a safe bypass. Flashboards. Temporary structures installed at the top of dams, gates, or spillways for the purpose of tem- porarily raising the pool elevation, and hence the gross head of a hydroelectric generating plant, thus increasing power output. Nonnally, flashboards are removed either at the end of the water storage season, or during periods of high stream-flow. Flexibility. The characteristics of a generating station or group of stations, which pennits shaping the energy pro- duced to fit a desired load shape or operating plan. Flood frequency curve. A curve that displays the exceedance frequency of floods for a range of peak flow values. Flood storage capacity. That portion of the reservoir capacity reserved for the temporary storage of floodwa- ters to reduce downstream flow. Flow-duration curve. A curve of flow values plotted in descending order of magnitude against time intervals, usually in percentages of a specified period. For exam- ple, the curve might show that one year, a river flows at 500 ft.3/s or more 10 percent of the time, and at 100 ft3fs or more 80 percent of the time. Forced outage. The shutdown of a generating unit for an emergency. Forced outage rate. The percent of a scheduled gener- ating time that a unit is unable to generate because of forced outages caused by mechanical, electrical, or other failures. G-6 Forced vortex. The rotation of a fluid, moving as a solid, about an axis where every particle of the fluid has the same angular velocity. Forebay. The impoundment immediately above a dam or hydroelectric plant intake structure. The term is appli- cable to all types of hydroelectric developments (i.e., storage, run-of-river and. pumped-storage). Form drag. The drag resulting from the shape of a body relative to the motion of the fluid stream. Fossil fuels. Coal, oil, and natural gas. Francis turbine. A Reaction turbine suitable for oper- ating at medium heads. Free vortex. Rotation of a fluid where each particle moves in a circular path with a speed varying inversely as the distance from the center. Frequency. The number of recurrences of a periodic phenomenon in a unit of time. Full-gate discharge. The discharge through a turbine when the turbine wicket gates are wide open. Gate. A closure device in which a leaf or closure mem- ber is moved across the fluid from an external position to control the flow of water. Gate-squeeze condition. The operating condition of a turbine with the wicket gates closed while maintaining maximum design spiral-case pressure. Gauging station. A particular site on a stream. canal, lake, or reservoir where systematic observations of streamflow or other hydrologic data are obtained. Generating unit. A single power-producing unit con- sisting of a turbine, generator, and related equipment. Generation. The act or process of producing electric energy from other forms of energy; also, the amount of electric energy so produced. Generator. A machine that converts mechanical energy into electrical energy. Generator speed. The rotating speed of the rotor com- ponent of the generator, normally expressed in number of revolutions per minute {rpm). Gigawatt (GW). One million kilowatts. Gigawatt-hour (GWh). One million kilowatt-hours. G-7 Governor. The device which measures and regulates turbine speed by controlling wicket gate angle to adjust water flow to the turbine. Gravitational constant (g). The rate of acceleration due to gravity, approximately 32.2 ft!s2. Gravity dam. A concrete dam that has sufficient mass to be inherently stable under all externally applied loads. Gross generation. The total amount of electric energy produced by a generating station or stations. Guard Gate. A gate that operates fully open or closed and functions as a secondary device for shutting off the flow of water in case the primary closure device becomes inoperable. Guard gates are usually operated under balanced pressure, no-flow conditions, except for closure in emergencies. Head. The difference in elevation between two water surfaces. Normally measured in feet or meters. Critical head. The hydraulic head at which the full- gate output of the turbine equals the generator rated capacity (full-gate referring to the condition where the turbine wicket gates are wide-open, thus permit- ting maximum flow through the turbine). Below criti- cal head, the full-gate turbine capability will be less than the generator rated capacity. Above critical head, generator rated capacity can be obtained at a dis- charge less than full-gate discharge. At many older plants, generators have a continuous overload rating. At these plants, critical head is defined as the head at which full-gate output of the turbine equals the gener- ator overload capacity. In recent practice, the term critical head is used to refer only to operating pro- jects. For planning and design purposes, the term 'rated head' is used to describe the same head condi- tions. Design head. The head at which the turbine will operate to give the best overall efficiency under vari- ous operating conditions Gross head. Tile difference of elevations between the water surfaces of the forebay and tailrace under spec- ified conditions. Net head. The gross head, less all hydraulic losses except those chargeable to the turbine. Rated head. Technically, the head at which a turbine at rated speed will deliver rated capacity at specified gate and efficiency. However, for planning and design purposes, rated head is identical to critical head. Hea~ gross (H). The difference in elevation between the headwater surface above and the tailwater surface below a hydroelectric power plant, under specified con- ditions. ASCE/EPRI Guides 1989 Head, net. Normally used in the context of head avail- ability to the turbine. It is equal to the gross head minus hydraulic losses in the wateiWays as the water passes from headwater to tailwater. Head, operating. Difference in elevation between the water surface forebay and tailrace with allowances for velocity heads. Head, suction. The head that a pump must provide on the inlet side to raise the liquid from the supply well to the level of the pump. Head gate. A closure device built in an intake to control inflow to the penstock, canal, or turbine inlet. Head losses. The various energy losses sustained as water flows from the headwater to the tailwater. Head losses through the turbine are normally accounted for in the turbine efficiency. Headcover. Stationary top part of a hydraulic turbine. Headrace. An open channel for conducting water to a power plant. Headwater. Water upstream of a dam or powerhouse. Headwater benefits. The benefits brought about by the storage and release of water by a reservoir project upstream. Application of the term is usually in reference to benefits realized at a downstream hydroelectric power plant. Headwater project. A storage reservoir located in the upper reaches of a river basin. Heat rate. A measure of generating station thermal effi- ciency, generally expressed as BTUs per net kilowatt- hour. It is computed by dividing the total BTU content of the fuel burned (or of heat released from a nuclear reactor) by the resulting net kilowatt-hours generated. Hertz. Cycles per second. Homologous. Having the same relative position, pro- ponion, value, or structure. Hot reserve. Reserve generating capacity in operation but not in service. House turbine. A turbine installed to provide a source of power to the powerhouse. Hydraulic capacity. The maximum flow which a hydroelectric plant can use to generate energy. ASCE/EPRI Guides 1989 Hydraulic head. A measure of energy or pressure, expressed in terms of the height of a column of water. Hydraulic loss. The loss in energy due to flow (friction and form loss). Hydraulic turbine. A machine that convens the energy of an elevated water supply into the mechanical energy of a rotating shaft. Hydroelectric plant (hydro or hydropower plant). An electric power plant containing turbine generators driven by falling water. Hydroelectric generator. An electric rotating machine driven by a hydraulic turbine that transforms mechanical power into electric power. Hydroelectricity. Electric power produced by hydro- electric generators. Hydrograph. A graphical representation of the varia- tions of the flow of a stream at a given station plotted in chronological order, usually with time as the abscissa and flow as the ordinate. Hydrologic availability (also Average availability). The ratio of the average capacity of a hydroelectric plant in the peak demand months to its rated capacity. This ratio accounts for variations in streamflow and head. Impeller. The rotating member of a turbine, blower, fan, axial or centrifugal pump, or mixing apparatus. Imports. Electric power which is transferred into a power system from another (usually adjacent) power system. Impon power is usually considered to be a gen- erating resource. Impoundments. Bodies of water created by erecting a barrier to flow, e.g. dams and diversion structures. Impulse turbine. A turbine that uses the kinetic energy of a high-velocity water jet to produce power. Induction generator. A nonsynchronous alternating- current generator that is driven above synchronous speed by external sources of mechanical power, normal- ly best suited to small hydroelectric plants. Inftow. The rate or volume of water that flows into a reservoir or forebay during a specified period. Installed capacity. The total of the capacities shown on the nameplates of the generating units in a hydropower plant. G-8 Intake. A structure to divert water into a conduit lead- ing to the power plant Interconnection. A transmission line joining two or more power systems allowing power produced by one system to be used by another. Internal rate of return. The discount rate that results in the Net present worth of a project being zero. Used in the economic evaluation of a project Intertie. See Interconnection. Intervention. A formal action taken by a person or group to ensure that its interests are addressed by FERC in the course of reviewing a license or exemption appli- cation. Jet. A fluid stream issuing from an orifice or nozzle. Journal. That part of a shaft in contact with and sup- ported by a bearing. Kaplan turbine. A propeller turbine in which the angle of the blades to the flow can be adjusted. Kilovolt (kV). One thousand volts. Kilovolt-ampere (kVA) rating. The output (in kW) of a generator divided by the power factor. Kilowatt (kW). One thousand watts. Kilowatt-hour (kWh). The amount of electrical energy involved with a one kilowatt demand over a period of one hour. Equivalent to 3.413 Btu of heat energy. Labyrinth seal. A minimum leakage seal that offers resistance to fluid flow while providing radial or axial clearance; a labyrinth of circumferential touch points that provide for successive expansion of the fluid. Laminar flow. Streamline flow of an incompressible viscous Newtonian fluid without turbulence in which all particles of the fluid move in distinct and separate lines. Leaf. The elliptically shaped section of a wicket gate. Leakage loss. Energy loss resulting from liquid leaking from a high-pressure zone of a machine to a low pres- sure zone. License. Approval from the Federal Energy Regulatory Commission to develop and operate a hydroelecttic pro- ject for a specified period of time. G-9 Line compensation. The balancing out of line impedance. Line impedance. The resistance to the flow of alternat- ing current that is analogous to the electrical resistance of direct current. Load (electrical). The amount of electrical power drawn from a power line, generator, or other power source. Load (mechanical). 1. The weight supported by a structure. 2. The mechanical force applied to a body. Load, average (electrical). The hypothetical constant load over a given time period that would produce the same energy output as the actual loading produced. Load, base. The part of the total load of an electrical power system that is applied, where possible, by the most efficient connected generating stations. Minimum load of a power generator over a given period of time. Load center. The point at which the loads of a given area are assumed to be concentrated for purpose of anal- ysis. Load, connected. The sum of the continuous ratings of the load-consuming apparatus connected to the system or part of the system under consideration. Load. The amount of electric power delivered at a given point Base load. The minimum load in a stated period of time. Intermediate load. That portion of the load between the base load and the peaking portion of the load. lntenuptible load. Electric power load which may be curtailed at the supplier's discretion, or in accordance with a contractual agreement. Peale load. The maximum load in a stated period of time. The peaking portion of the load is that portion of the load that occurs for less than eight hours per day. Load curve. A curve showing power (kW) supplied, plotted against time of occurrence, and illustrating the varying magnitude of the load during the period cov- ered. Load diversity. 1be difference between the sum of two or more individual peak loads and the coincident or combined maximum load. ASCE/EPRI Guides 1989 Load duration curve. A curve showing the total time, within a specified period, during which the load equalled or exceeded the power values shown. Load factor. The ratio of the average load during a des- ignated period to the peak or maximum load occurring in that period. Load, peak (electrical). Maximum load consumed or produced by a unit or group of units in a stated period of time. Load rejection. A fault condition that rapidly decreases the electrical load on the generating unit to no load. Normally caused by either a fault in the utility transmis- sion system with which the generating unit is intercon- nected or a malfunction within the generating unit or its auxiliaries. The capability to shut down the turbine in such a way as to avoid damage due to overspeed or waterhammer is important when load rejection occurs. Load-resource analysis. A year-by-year comparison of expected power loads with existing and scheduled gener- ating resources, which is undertaken to determine when additional generating resources will be required. Log boom. A device used to prevent large objects float- ing on the water surface from entering an area. Normally used upstream of an intake or spillway. Loss. Consumptive loss. Water that is removed from a reservoir and not subsequently returned to down- stream flow. Examples are evaporation and with- drawals for irrigation and water supply. Electric system loss. Total electric energy loss in the electric system. It consists of transmission, transfor- mation, and distribution losses, and unaccounted-for energy losses between sources of supply and points of delivery. Energy loss. The difference between energy input and output as a result of transfer of energy between two points (see also Line loss). Head loss. Reduction in generating head due to fric- tion in the water passage to the turbine: includes trashrack, intake, and penstock friction losses. Line Loss. Energy loss and power loss on a transmission or distribution line. Nonconsumptive loss. Water that is unavailable for a specific project purpose but which is included in downstream flow from a project Examples are losses due to seepage, turbine leakage, and the operation of navigation and fish passage facilities. Power loss. The difference between power input and output as a result of transfer of energy between two ASCEIEPRI Guides 1989 points (sometimes referred to as "Capacity Loss") (see also Line loss). Transmission Loss. Same as line loss. Low-head hydropower. Hydropower that operates with a head of 66 feet (20 m) or less. Manifold. A section of steel pipeline that divides flow from a single penstock into several smaller penstocks that feed multiple turbine generator units. Margin. The difference between the net system generat- ing capability and system maximum load requirements including net schedule transfers with other systems. Market value. The value of power at the load center as measured by the cost of producing and delivering equiv- alent alternative power to the market. Marketability. The generating output of a proposed powerplant is marketable if it can be used in the system load and the fixed and variable costs of the plant can be recovered with interest within an appropriate period of time. Mass curve. A cumulative plot of reservoir inflow ver- sus time. Mechanical loss. Energy loss due to mechanical friction between fixed and moving parts, e.g., rubbing or sliding friction between a rotating shaft and its bearing. Megawatt (MW). One thousand kilowatts. Megawatt-hours (MWh). One thousand kilowatt· hours. Meridional. Marked with lines in the plane of the axis. Meridional plane. A plane containing the runner axis. Mill. One-tenth of one cent. Minimum discharge. Project minimum discluzrge. The minimum flow that must be released from a project in order to meet envi- ronmental or other non-power water requirements. Turbine minimum discharge. The minimum permis- sible discharge through a turbine. Mitigation measure. Any type of feature (i.e., struc- tural, operational, etc.) incorporated into the design of a hydro project to reduce environmental impact. G-10 Momentum. The quantity of motion possessed by a body. It is measured by the product of the mass of the body and its velocity. Multiple~purpose reservoir. A reservoir planned to operate for more than one purpose. Multipurpose river basin program. A program for the development of a river with a darn and related structures that serves more than one purpose, such as hydroelectric power, irrigation, water supply, water quality control, and fish and wildlife enhancement. Municipal preference. FERC rule for deciding between competing applications for project licenses by which municipal developers receive priority over nonmunicipal developers, all other criteria being equal. Natural frequency. The frequency at which a body will oscillate if disturbed from its equilibrium position. Net present worth. The difference between the present worth of benefits and the present worth of costs over the life of the project. Net positive suction head. The minimum suction head required for a pump to operate: depends on the liquid characteristics, total liquid head, pump speed and capac~ ity, and impeller design. Abbreviated NPSH. Newton. The unit of force in the SI system. One Newton is the force required to impan to a mass of 1 kg, an acceleration of 1 mJs2. Notice of Intent. Formal notice that a competing appli- cation for a license or preliminary permit will be filed. By flling a Notice of Intent, a competing applicant may file the actual application after the deadline specified in the public notice of the initial application. Notice period. A specified period of time during which the public must be notified of an application pending before FERC. Interventions and Notices of Intent must be filed during the notice period. Nozzle. A control valve that directs flow onto the runner of a Pelton or Turgo impulse turbine. Nuclear Power. Power released from the heat of nuclear reactions, which is convened to electric power by a tur- bine generator unit. Operating policy (operating rule curves). The techni- cal operating guide adopted for water resources projects to ensure that authorized output of the project is G-11 achieved. Usually in the form of charts and graphs of reservoir release rates for various operational situations. Operation factor. The ratio of the duration of the actual service of a machine or equipment to the total duration of the period of time considered. Outage. The period during which a generating unit, transmission line, or other facility is out of service. Forced outage. The shutting down of a generating unit, transmission line, or other facility for emergency reasons. Maintenance outage. The removal of a generating unit from operation for required maintenance. Scheduled outage (planned outage). The shutdown of a generating unit, transmission line, or other facility for inspection or maintenance in accordance with a predetermined schedule. Output factor. The ratio of the actual energy output, in the period of time considered, to the energy output that would have occurred if the machine or equipment had been operating at its full rating throughout its actual hours of service during the period. (In) Parallel. Several units whose a-c frequencies are equal and which operate synchronously as part of the same electric system. · Pascal. A unit of pressure equal to a force of 1 Newton acting uniformly over an area of 1 square meter. Peak demand months. The month or months of highest power demand. Peak load. The maximum load in a stated period of time. Peaking. As distinguished from run-of-river, a type of hydro project that uses its reservoir as a storage facility, releasing water to generate power only when power is needed (usually during peak demand periods). Peaking capacity. That part of a system's capacity that is operated during the hours of highest power demand. Peaking units. Usually old low-efficiency units, gas tur- bines, diesel engines, or pumped storage hydroelectric units used primarily during the peak load periods. Pelton turbine. An impulse hydraulic turbine normally used for high-head hydroelectric plants, but sometimes suitable for moderate heads at smaller hydro sites. The turbine works on the impact of high-velocity jets of water on a series of buckets fixed around the edge of the runner. ASCEJEPRI Guides 1989 Penstock. The high-pressure conduit extending from the first upstream water surface to the turbine. Period of record. The historical period for which streamflow records exist Pitting. Corrosion of metal surfaces caused by local chemical action. Plant (station). Base load plant. A power plant normally operated at a constant load. Conventional hydroelectric plant. A hydroelectric power plant utilizing falling water only once as it passes downstream, as contrasted to either a pump- back or pumped-storage plant, which recirculates all or a ponion of the streamflow during the production of electric power. Combined cycle plant. An electric power plant con- sisting of a series of combustion turbines with heat extractors on their exhausts. Combustion turbine plant. An electric power plant consisting of natural gas or distillate oil-fired jet engines connected to a generator. Energy displacement plant. A power plant (usually hydroelectric), whose output is used to displace gen- eration from existing high-cost thermal plants. Fossil-fuel plant. An electric power plant using fossil fuels (coal, lignite, oil, or natural gas) as its source of energy. Nuclear power plant. An electric generating station using the energy from a nuclear reactor as its source of power. Peak load (peaking) plant. A power plant which is normally operated to provide power during maximum load periods. Pondoge plant. A hydroelectric plant with sufficient storage to permit daily or weekly shaping of stream- flows. Power plant (powerplant). A generating station where prime movers (turbines), electric generators, and auxiliary equipment for producing electric energy are located. Pump-back hydroelectric plant. An on-stream pumped-storage project. This type of plant utilizes a combination of natural streamflow and pumped water as its source of energy. Pumped-storage hydroelectric plant. A hydroelectric power plant that generates electric energy by utilizing water pumped into a storage reservoir, usually during off-peak periods. The two major types of pumped- storage hydroelectric plants are pumpback and off- stream pumped-storage plants. Run-of-river plant. A hydroelectric power plant that uses pondage or the flow of the stream as it occurs. ASCE/EPRI Guides 1989 Steam-electric plant. An electric power plant that uses steam as the motive force of its prime movers. Steam plants can be either nuclear or fos- sil fuel fired, or they can utilize geothermal ener- gy. Storage plant. A hydroelectric plant constructed at a reservoir that provides storage. Thermal plant. An electric power plant which derives its energy from a heat source, such as combustion, geothermal water or steam, or nucle- ar fission. Includes fossil-fuel and nuclear steam plants and combustion turbine and combined cycle plants. Plant factor. The ratio of the average load to the installed capacity of the plant, expressed as an annu- al percentage. (See Capacity factor.) Pondage. Water stored behind a dam used for daily or weekly regulation of the flow of a river. Power. The time rate of transferring energy. Electrical power is measured in kilowatts. The term is also used in the electric power industry to mean inclusively both capacity (power) and energy. Continuous power. Hydroelectric power available from a plant on a continuous basis under the most adverse hydraulic conditions contemplated. Same as prime power. Firm power. Power intended to have assured availability to the customer to meet all or any agreed upon ponion of his load requirements. Interruptible power. Power made available under agreements which permit cunailment or cessation of delivery by the supplier. Nonfirm power. Power which does not have assured availability to the customer to meet his load requirements. Prime power. Same as continuous power. Seasonal power. Power generated or made avail- able to customers only during certain seasons of the year. Power, dump. Hydroelectric power in excess of load requirements that is made available by surplus watet Power, finn or primary. The power that a plant can be expected to deliver 100 percent of the time. Power, generating station auxiliary. The power required for operation of the generating station auxil- iaries. Power, prime. The maximum potential power con- stantly available for transformation into electric power. G-12 Power benefits. The monetary benefits associated with the output of a hydroelectric plant Power, surplus or secondary. All power in excess of finn power. Power factor. The phase relationship between alternat- ing current and voltage. A power factor of 1 indicates that peak current and voltage cycles are synchronized. A power factor lower than 1 indicates that inductive or capacitive effects have displaced the synchronization of current and voltage cycles. Low power factor reduces the efficiency of power transmission. Power values. Annualized unit costs of constructing and operating the thennal alternative to a hydroelectric plant. At-market (or at-load center) value. The value of pewer at the market as measured by the cost of pro- ducing and delivering equivalent alternative power to the market. At-site value. The value of power at the site of the hydro-electric plant as measured by the at-market value minus the cost of transmission facilities and losses from the hydroelecUic plant to the load center. The amount of power at the site is more than the amount of power at the market due to transmission losses. Capacity value. That part of the at-site or at-market power value which is assigned to capacity. Energy value. That part of the at-site or at-market power value which is assigned to energy. Fuel displacement value. The value of electric energy, usually hydro, which may be substituted for energy generated in a fuel-electric plant, in tenns of the incre- mental cost of producing the energy in the fuel-electric plant. Power pool. Reservoir power pooL That portion of a reservoir's storage capacity which is allocated to the storage of water for power production. Electric Power PooL Two or more interconnected electric power systems that are coordinated to supply power in the most economical manner for their com- bined loads. Powerhouse. A structure that houses the turbines, gener- ators, and associated control equipment. Preliminary permit. A permit granted by FERC for a particular project site, giving the holder priority status for filing an application for a license or exemption. A pre- liminary pennit may be granted for a tenn of up to 36 months, and is not renewable. Obtaining such a pennit is an optional step in the licensing process. G-13 Pressure rise. The operating condition of a pump tur- bine corresponding to a full load rejection and a rapid wicket gate closure. Pressure shaft. A vertical or inclined conduit excavat- ed in rock and capable of carrying water under pres- sure. In underground hydroelecUic projects it replaces the penstock. Prime mover. The engine, turbine, waterwheel, or similar machine that converts a natural source of ener- gy into mechanical energy. Project sponsor. The entity controlling the hydro site and promoting construction of the facility. Propeller. A bladed device that rotates on a shaft to produce a useful thrust in the direction of the shaft axis. Propeller blade. One of two or more plates radiating out from the hub of a propeller turbine. Propeller turbine. An axial flow reaction turbine. i.e., the flow moves parallel with the axis of the turbine shaft. The turbine runner is similar to a ship's propeller and the turbine is used for low-and ultralow-head hydro projects. If the angle of the blades to the flow can be adjusted, the turbine is called a Kaplan turbine. Pump. A machine driven by a prime mover and used to move fluids from a low to a high pressure level. Pumped storage. A method of energy storage in which low~cost electrical energy produced during low demand periods is used to pump water into an elevated reservoir from which water is released during high demand periods to supply high-value electrical energy. Pumped storage hydroelectric plant. A power plant where power is produced during peak load periods by using water previously pumped from a lower reservoir to an upper reservoir during off-peak periods. Pumping. The operation of a pump turbine in the pump cycle with the wicket gates in the position corre- sponding to maximum gate torque. Pump prime. The conditions associated with staning (priming) the pump against closed wicket gates. Pump shutoff. The operating condition for a pump turbine corresponding to the release of the pressurized air after a pump start. ASCE/EPRI Guides 1989 Pump/turbine. A hydraulic machine that can be used alternately as a pump and prime mover (turbine). Ramp rate. The maximum allowable rate of change in output from a power-plant. The ramp rate is established to prevent undesirable effects due to rapid changes in loading or, (in the case of hydroelectric plants), discharge. Race. A channel transporting water to or away from hydraulic machinery, as in a power house. Rake. A toothed device for removing debris from trash racks. Rated head. The net hydraulic head at which the tur- bine produces the generator's rated output. Normally measured in feet or meters. Rated output. The power output at which a turbine or generator is rated; this normally corresponds to the out- put at the selected design point of head and flow. Normally measured in kilowatts (kW) or megawatts (MW). Rate of return on investment. The interest rate at which the present worth of annual benefits equals the present worth of annual costs. Reaction turbine. A generic term for hydraulic turbines in which water enters the runner under pressure and interacts with the turbine runner in such a way that the hydraulic energy is converted to kinetic energy in the turbine shaft. Reaction turbines include Francis, fixed- blade propeller, Kaplan, and semi-Kaplan. Crossflow or Banki turbines work on a combination of impulse and reaction r · nciples. Pelton and Turgo turbines are impulse turomes. Reconnaissance study. A preliminary feasibility study designed to ascertain whether a full feasibility inves- tigation is warranted. Also called an Appraisal study or prefeasibility study. Reregulating reservoir. A reservoir located down- stream from a hydroelectric peaking plant. that has suf- ficient capacity to store the fluctuating discharges from the peaking plant and to release them in a relatively uni- form manner downstream. Reserve. The additional capacity of a power system that is used to cover contingencies, including maintenance, forced outages, and abnormal loads. Cold reserve. Thermal genemting capacity available for service but not maintained at operating tempem- ture. ASCEIEPRI Guides 1989 Hot reserve. Thermal generating capacity maintained at a temperature and condition which will permit it to be placed into service promptly. Spinning reserve. Generating capacity connected to the bus and ready to take load. It also includes capaci- ty available in generating units which are operating at less than their capability. Standby· reserve. Reserve capacity which can be placed on-line in a matter of minutes. Includes hot reserve capacity, combustion turbines, and most idle hydroelectric capacity. System required reserve. The system reserve capacity needed as standby to insure an adequate standard of service. Reserve equipment. Installed equipment in excess of that required to carry peak load. Reservoir storage. Active storage. The portion of the live storage capaci- ty in which water normally will be stored or with- drawn for beneficial uses, in compliance with operat- ing agreements or restrictions. Conservation storage. That portion of the water stored in a reservoir that is impounded for later use. Synonymous with active storage. Conservation stor- age is the portion of a reservoir's live storage that is normally conserved for beneficial use at-site or downstream but does not include any live storage space reserved exclusively for flood control. Dead storage. The volume of a reservoir which is below the inven. of the lowest outlet and cannot be evacuated by gmvity. Flood control storage space. Reservoir storage space that is kept available for impounding potential flood flows. Exclusive flood control storage space is evacu- ated as soon as streamflows recede to the point when stomge releases can be made without exceeding chan- nel bankfull capacity. Seasonal flood control storage space is discussed under joint use storage. Inactive storage. The pon.ion of the live storage capacity from which water normally will not be with- drawn, in compliance with operating agreements or restrictions. Joint Use storage. Storage space that is used for flood control for pan. of the year and to impound con- servation stomge during the remainder of the year. Uve storage. The volume of a reservoir exclusive of dead and surcharge storage capacity. Pondage. Reservoir storage capacity of limited magnitude, that provides only daily or weekly regulation of stream- flow. Power ltOI'tlge. Conservation stomge that is regulated for hydroelectric power genemtion. G-14 Seasonal storage. Reservoir storage capacity of suffi- cient magnitude to permit carryover from the high flow season to the low flow season, and thus to devel- op a firm flow substantially greater than the minimum natural flow. Storage capacity. The volwne of a reservoir available to store water. Resonance. That point at·which the resulting amplitude of oscillation of a physical system becomes large when the frequency of the excitation equals a natural frequen- cy of the system. Revenue. The income earned by a hydroelectric project. Revenue stream. All the incoming monies generated by a hydroelectric project over time. Reversible pump/turbine. A hydraulic prime mover that operates as a pwnp in one direction of rotation, and as a turbine in the opposite direction of rotation. Through design trade-offs, good efficiencies can be achieved in both modes of operation. Reversible unit. The combination of a motor/generator and pwnp/turbine. Riprap. Large stones or concrete placed for the purpose of protecting a slope from water erosion. Rotor. The rotating inner portion of a generator consist- ing of windings surrounding the field poles, which are dovetailed to the periphery of a laminated core. Rule curve. A curve or family of curves indicating how a reservoir is to be operated under specific conditions to obtain best or predetermined results. Rule curves can be designated to regulate storage for flood control. hydropower production, and other operating objectives, as well as combinations of objectives. Run-of-river. A type of hydro project that releases water at the same rate as the natural flow of the river (outflow equals inflow). Runaway speed. The speed (in rpm) of the turbine nm- ner under the condition of full open gate but no electri- cal load occurs when the hydro unit is tripped off the line while the unit is generating. Runner. The part of a hydraulic turbine that transforms the pressure and kinetic energy of the water into useful work. As the water flows through the turbine, it changes direction, which creates a force on the runner and causes it to rotate. G-15 Runner blades. The propeller-like vanes of a hydraulic turbine that conven the kinetic energy of the water into mechanical power. Runoff. The ponion of precipitation that runs over the land surface and forms Streamflow. Scheduled outage. The shutdown of a generating unit for planned maintenance. Scroll case. A spiral waterway normally made of either reinforced concrete or steel that guides water to the run- ner of a reaction turbine. Seasonal diversity. Diversity between two or more power systems when their annual peak loads occur dur- ing different seasons of the year. Secondary energy. Nondependable energy from a hydro project that may not be available at times because of low water conditions. Sequential streamflow routing (SSR). The chronologi- cal routing of streamflows through a project or system of projects in order to defme a project's firm yield, its ener- gy or peaking power output, or its performance under specified operating criteria. Series capacitors. A bank of capacitors connected in series with an electric power transmission line that is used to control the magnetic component of line impedance. Service area. Territory in which a utility system is required to (or has the right to) supply or make available electric service to ultimate conswners. Service outage. The shutdown of a generating unit, transmission line, or other facility for inspection, mainte- nance, or repair. Servomechanism. An automatic feedback control sys- tem for mechanical motion; it applies only to those sys- tems in which the controlled quantity or output is mechanical position or one of its derivatives (velocity, acceleration, etc.). Servomotor. The electric, hydraulic, or other type of motor that serves as the final control element in a ser- vomechanism; it receives power from the amplifier ele- ment and drives the load with a linear or rotary motion. Settling basin. A chamber designed to remove sediment from water by providing quiescent conditions that allow sediment to fall to the floor of the chamber. They are ASCEIEPRI Guides 1989 used in cases where sediment would otherwise block waterways or damage the turbine. Shear-pin-failure condition. The operating condition of a turbine with the wicket gates in a nearly closed position with only two gates interacting because an obstruction is wedged between them. Shunt capacitors. Capacitors connecting from a power line to a grounded connection, usually designed to reduce that part of the electric current causing a poor power factor. Slide gate. A hydraulic gate that operates in vertical guides and has no wheels, rollers, or other friction- reducing devices. Nonnally, such a gate must be opened or closed under balanced head conditions. Sluice gate. A vertical-shaft Slide gate often used for passing water through a dam. Manual or motor-operat- ed floor stands are used to raise and lower sluice gates. Small hydropower. Hydropower installations that are IS,O<X> kW (15 MW) or less in Capacity. Spare equipment. Equipment complete or in parts, on hand for repair or replacement Spear. The needle inside the nozzle for a Pelton turbine. Specific speed. A factor used to compare hydraulic characteristics of turbines or pumps. Speed increaser. A mechanical device installed between the generator and the turbine that pennits the generator to operate at a higher speed. They are used on low-head pro- jects to reduce the size and cost of the generator. Speed ring. See Stay ring. Spherical value. A heavy-duty valve generally used for penstock shutoff purposes on high-head projects. The valve body consists of a rotating sphere that provides a full port in the open position. Double seals of a retractable type are generally provided. Spill. The discharge of water through gates, spillways, or conduits which bypasses the turbines of a hydroelec- tric plant Spillway. An outlet from a reservoir or section of a dam designed to release surplus water that is not discharged through a turbine or other outlet works. Spillway design flood. The pattern of flood inflow (hydrograph) used to size the spillway gates and ASCE/EPRI Guides 1989 determine the required freeboard for dam design pur- poses. Spinning reserve. Generating units operating at no load or at partial load with excess capacity readily available to support additional load. Spiral case. A steel-lined conduit connected to the pen- stock or intake conduit that evenly distributes water flow to the turbine runner. Standby equipment. Generating equipment not nonnal- ly used but available, through a pennanent connection, to replace or supplement the usual source of supply. Station use. Energy power used in a generating plant as necessary in the production of electricity. It includes energy consumed for plant light, power, and auxiliaries regardless of whether such energy is produced at the plant or comes from another source. Stator. The stationary outer portion of a generator con- sisting of a frame, laminated magnetic core, and anna- tore windings that carry heavy currents and high volt- ages. Stator armature. A stator that includes the main cur- rent-carrying winding in which electromotive force pro- duced by magnetic flux rotation is induced; it is found in most ac machines. Stay ring. A structural part of a hydraulic turbine that contains the stay vanes and to which the spiral case and headcover are attached. Stay vanes. Curved, airfoil-shaped, stationary surfaces located between the spiral case and wicket gates in a hydraulic turbine whose purpose is to induce a prerota- tion or prewhirl to the fluid to reduce the relative veloci- ty to the runner. Tiley also serve as columns that aid in supporting the generator weight and the loads associated with the internally pressurized machine. Steam plant. An electric power plant that uses steam as the motive force of its prime movers. Steam plants can be either nuclear or fossil fuel-fired, or they can use geothennal energy. Stiffness. The ratio of a steady force acting on a defonnable elastic medium to the resulting displacement. Stilling basin. The area on the downstream side of a spill- way where water velocity is reduced to prevent erosion damage to hydraulic structures or the natural riverbed and banks. G-16 Stoplog. See Bulkhead gate. Storage draft. Stored water released from a reservoir during a specified interval of time, thereby lowering the elevation of the water surface in the reservoir. Storage project. A project with a reservoir of sufficient size to permit canyover from the high-flow season to the low-flow season, and thus to develop a firm flow sub- stantially more than the minimum natural flow. A stor- age project may have its own powerplant or may be used only for increasing generation at some downstream plant. Storage reservoir. The volume behind a dam used to store water. Streamflow. The rate at which water passes a given point in a stream, usually expressed in cubic feet per second. Average streamflow. The average rate of flow at a given point during a specified period. Critical streamflow. See Critical streamflow. Depleted streamflow. Streamflow which has been adjusted to remove existing or projected withdrawals or diversions for irrigation or municipal and industrial water supply. Maximum streamflow. The maximum rate of flow at a given point during a specified period. Median streamflow. The rate of flow at a given point for which there are equal numbers of greater and less- er flow occurrences during a specified period. Minimum streamflow. The minimum rate of flow at a given point during a specified period. Natural streamflow. Streamflow at a given point of an uncontrolled stream, or regulated streamflow which has been adjusted to eliminate the effects of reservoir storage or upstream diversions. Regulated streamflow. 1be controlled rate of flow at a given point during a specified period resulting from reservoir operation. Streamline. A line that is everywhere parallel to the direction of fluid flow at a given instant Stress. Force per unit area as for a solid material resist- ing compression, tension, or external forces. Stress concentration factor. A factor expressing the ratio of the greatest stress in the region of stress concen- tration to the corresponding nominal stress. Stress raiser. A notch, hole, or other discontinuity in contour or structure that causes localized stress concen- tration. G-17 Submergence. The elevation of the runner or impeller relative to the tailwater elevation to mitigate the effects of cavitation. Surge tank. A hydraulic structure designed to control pressure and flow fluctuations in a penstock or tunnel . It functions as a reservoir that temporarily stores or releases water to the turbine. Surplus power. Generating capacity that is not needed in the system when it is available. Switchyard. A concentration of electrical equipment which connects two or more electric circuits through switches, selectively arranged in order to permit a cir- cuit to be disconnected or to change the electric connec- tion between the circuits. In a hydroelectric project, the switchyard is the point at which the energy generated at the project is connected to the distribution system Switchgear. The switches, breakers, and other devices used for opening or closing electrical circuits and con- necting or disconnecting generators, transformers, and other equipment. Synchronous condenser (capacitor). A synchronous motor running without mechanical load and drawing a large leading current, like a capacitor, used to improve the power factor and voltage regulation of an ac power system. Synchronous generator. An ac generator whose oper- ating speed is fixed by the frequency of the electrical system to which it is interconnected. Synchronous machine. An ac machine whose average speed is proportional to the frequency of the applied or generated voltage. Synchronous motor. A synchronous machine that transforms ac electric power into mechanical power, using field magnets excited with direct current. Synchronous speed. The speed of rotation of a syn- chronous machine; in revolutions per second. It is equal to twice the frequency of the alternating current in hertz divided by the number of poles in the machine. System (electric). Electric power generation, transmis- sion, distribution, and other facilities operated as an integral unit. System reserve. The capacity, in equipment and con- ductors. installed on the system in excess of that required to carry the peak load. ASCE/EPRI Guides 1989 Tailrace. A channel for conducting water away from a power plant after it has passed through it. Sometimes called an afterbay. Tailwater. Water surface downstream of the power- house. Tailwater elevation. The elevation of the water surface downstream from a dam or hydroelectric plant Tailwater rating curve. The curve that depicts tailwa- ter elevation at different streamflows. Tap. A connection from one transmission line to anoth- er or to a substation. Thermal plant. An electric power plant which derives its energy from a heat source, such as combustion, geothermal water or steam, or nuclear fission. Includes fossil-fuel and nuclear steam plants and combustion tur- bine and combined cycle plants. Thrust. The reaction to a compressive force on a rod. Thrust bearing. A bearing that supports the entire weight of both the rotating parts of a vertical-shaft tur- bogenerating unit and the maximum hydraulic thrust developed by the turbine. Tie line. A transmission line connecting two systems. Timber crib dam. A dam constructed of timber crib cells filled with rock ballast and covered with sheathing on the water side to minimize leakage. Time zone diversity. The diversity between systems in different time zones resulting from time differences as it affects the demand for power. Torque. The turning moment exerted by a tangential force acting at a distance from the axis of rotation or twist Torque converter. A device for changing the torque speed or mechanical advantage between an input shaft and an output shaft. Torsion. A twisting deformation of a solid body about an axis in which lines that were initially parallel to the axis becomes helices. Torsional vibration. A periodic motion of a shaft in which the shaft is twisted about its axis in one direction and then in the other. This motion may be superimposed on rotational or other motion. ASCE/EPRI Guides 1989 Transformer. An electromagnetic device used to change the voltage of ac electricity. Transmission. The transporting or conveyance of elec- tric energy in bulk to a convenient point, where it is sub- divided for delivery to the distribution system. Also used as a generic term to indicate the conveyance of electric energy over any or all of the paths from source to point of use. Transmission lines. The wire or cable system used to conduct electric power. Transient. That period during which events are chang- ing with time. Trashrack. A rack or screen of parallel bars installed to prevent debris from entering the turbine. Tubular turbine. An axial-flow, propeller turbine that may have a vertical, horizontal, or inclined shaft. Turbidity. The extent to which water has become clouded as a result of suspended sediments. Turbine. A machine which, in the case of a hydroelec- tric plant, converts the energy of water to mechanical energy. Turbine classes. Modem hydraulic turbines are divided into two classes: impulse and reaction turbines. Impulse turbine. Has one or more free jets that dis- charge into an aerated space and impinge on the buckets of the runner. Has a means of controlling the rate of flow, housing, and a discharge passage. Reaction turbine. Has a water supply case, a mecha- nism for controlling the quantity of water and for dis- tributing it equally over the entire runner intake, and a draft tube. The water supplies energy to the runner in kinetic form. G-18 Francis turbine. A reaction turbine having a run- ner with a large number of fixed buckets, usually nine or more, to which the water is supplied in a whirling radial direction. It can be designed for operating heads ranging from 50 to 2,000 feet. Adjustable-blade propeller turbine (Kaplan). A reaction turbine having a runner with a small num- ber of blades, usually four to eight, to which the water is supplied in a whirling axial direction. The blades are angularly adjustable in the hub. Fixed-blade propeller turbine. A reaction turbine having a runner with a small number of blades, usually four to eight, to which the water is sup- plied in a whirling axial direction. The blades are rigidly fastened to the hub. Turbine-generator. The primary components of a hydro unit. See Turbine and Generator. Turbine runner. The central rotating component of a hydraulic turbine that converts hydraulic energy to mechanical energy. Otherwise known as the turbine wheel. It normally consists of a series of curved vanes, blades, or buckets attached to a central rotating hub. Turbining. The operation of a turbine or a pump turbine with the wicket gates in a position corresponding to maximum gate torque. Turbomachine. A device in which energy transfer occurs between a flowing fluid and a rotating element due to dynamic action, and results in a change in pres- sure and momentum of the fluid. Turgo turbine. An impulse turbine used at the lower end of the high hydraulic head range. The turbine works on the impact between high-velocity water jets and the runner blades. The jets are directed onto the surface of the turbine runner at an angle to the runner shaft. Unwatering. Dewatering. Uprating. Increasing the generating capacity of a hydropower plant by either replacing existing equip- ment with new equipment or improving the existing equipment. Usable storage. That portion of the gross storage that may be used for an authorized purpose. Utilization factor. The ratio of energy output to avail- able energy within the capacity and characteristics of the plant Valve. A closure device for controlling the flow of water. Vane. A flat or curved surface exposed to a flow of fluid so as to be forced to move or to rotate about an axis, to rechannel the flow, or to act as the impeller. Vertically integrated system. A power system that combines generation, transmission, and distribution functions. Voltage (circuit). The electric potential difference between conductors or between conductors and ground, usually expressed in volts (V) or kilovolts (k.V). Volute. A spiral casing for a centrifugal turbomachine designed so that speed will be converted to pressure without shock. G-19 Vortex. A flow with closed streamlines. Vortex line. A line drawn through a fluid such that it is everywhere tangent to the vorticity. Vorticity. For a fluid flow, a vector equal to the curl of the velocity of flow. Water conditions. Adverse water conditions. Water conditions limiting the production of hydroelectric power, either because of low water supply or reduced gross head or both. Also sometimes called critical water conditions. Average water conditions. Precipitation and runoff conditions which provide water for hydroelectric power development approximating the average amount and distribution available over a long time period, usually the period of record. Critical water conditions. Same as Adverse Water Conditions. Median water conditions. Precipitation and runoff conditions which provide water for hydroelectric development approximating the median amount and distribution available over a long time period, usually the period of record. Waterhammer. Pressure changes in a pressure conduit or penstock that are caused by the flow variation with time. Water passage. Conduits that convey water to and from the turbine runner. They include the scroll case, distribu- tor, and draft tube. Waterwheel. A vertical wheel on a horizontal shaft that is made to revolve by the action or weight of water on or in containers attached to the rim. Watt (W). The rate of energy transfer equivalent to 1 ampere under a pressure of 1 volt at unity power factor. Wear. Deterioration of a surface due to material removal caused by relative motion between it and anoth- er part Wearing rings. Replaceable rings installed in the casing or impeller (runner), or both, to take the wear resulting from rotation of the impeller, grit, and other abrasives in the liquid. Wheeling. The transfer of power and energy from one utility over the transmission system of a second utility for delivery to a third utility, or to a load of the first utility. Wicket gates. Adjustable vanes that surround a reaction turbine runner and control the area available for water to enter the turbine. ASCE!EPRI Guides 1989 MEASUREMENT CONVERSIONS ACCELERATION Unit 1 Foot per second squared (ftls2) 1 Meter per second squared (mJs2) AREA Unit ftl ml 1 Square foot (ft2) 1 0.0929 1 Square meter (m3) 10.7639 1 1 Hectare (ha) 1.0764x10S 10.000 1 Acre 43,560 4046.85 1 Square mile (mi2) 2.7878x107 2.5900X 1 ()6 ENERGY Unit J ft-lb Btu ftlsl 1 3.2808 ha 9.2903xiQ-6 1x1o-4 1 0.4047 259 kcal 0.3048 1 Acre 2.2956x 1 o-5 2.4711x1Q-5 2.4711 1 640 hph 1 Joule (J) 1 0.7376 9.481xlo-4 2.389x1Q-4 3.725xto-7 1 Foot-pound (ft-lb) 1.356 1 1.285xtQ-3 3.239x1Q-4 5.051x10·7 I British thennal unit (Btu) 1,055 777.9 1 0.252 3.929x1Q-4 I Kilocalorie (kcal) 4,086 3,087 3.968 1 1.559x1Q-3 1 Horsepower-hour (hph) 2.685x1Q6 1.980X106 2.545 641.4 1 1 Kilowatt-hour (kWh) 3.6xlQ6 2.655x1Q6 3,413 860.1 1.341 FORCE Unit dyn N lbf kgf kip mil 3.587x1Q-8 3.8610X10-7 3.861Qx1Q-3 1.5625xtQ-3 1 kWh 2.778x10·7 3.766xt0·7 2.930Xl04 1.163x1Q-3 0.7457 1 1 Dyne (dyn) 1 l.OX1Q-5 2.248x1Q-6 1.020XI0-6 2.248x10-l0 I Newton(N) IOO,OOO 1 0.2248 0.1020 2.248x1Q-4 I Pound (lbt) 444,800 4.448 1 0.04536 0.001 I Kilogram (kgt) 980,700 9.807 2205 I 2.205x1Q-3 1 Kip 4.448x1Q9 4,448 1,000 453.5 1 M-1 MEASUREMENT CONVERSIONS-Continued LENGTH Unit in ft m km mi 1 Inch (in) 1 0.0833 0.0254 2.540xiQ-5 1.5782xto-5 1 Foot (ft) 12 1 0.3048 3.048x104 1.8939><104 1 Meter (m) 39.3710 3.2808 1 0.001 6.2136x 1Q-4 1 Kilometer (km) 39,370 3,280.84 l,ro> 1 0.6212 1 Mile (mi) 63,360 5,280 1,609.36 1.6093 1 MASS Unit lb kg Metric slug Slug Metric ton Longton 1 Pound (lb) 1 0.4536 0.0462 0.0311 4.536x1Q-4 446.4x104 1 Kilogram (kg) 2.205 1 0.1020 0.0685 0.001 9.842x104 1 Metric slug 21.62 9.807 1 0.6721 0.0098 0.0096 1 Slug 32.17 14.59 1.490 1 0.0146 0.0144 1 Metric ton 2,205 l,ro> 102.0 68.52 1 0.9842 1 Long ton 2,240 1,016 103.7 69.63 1.016 1 POWER (Rate of Energy Flow) Unit Btu/h fl-lb/s hp kW 1 Btu/hour (Btu/h) 1 0.2161 3.929><104 2.920x104 1 Foot-pound/second (ft-lb/s)4.628 1 1.818xto-3 1.356.10-4 1 Horsepower (hp) 2,545 550 1 0.7457 1 Kilowatt (kW) 3,413 737.6 1.341 1 1 Watt = 1 1/s. 1 kW is generated by 11.81 ft3fs of water falling 1 foot (at 100% efficiency) or by 0.102 m3fs falling 1 meter (at 100% efficiency). PRESSURE Unit Pa H1on Hgin lbfinl atm 1 Pascal (Pa) 1 3.3456x10-4 2.9533x1Q-4 1.4504x1Q-4 9. 8692x 1 Q-6 1 Foot of water @39.4 Of' (H~ ft) 2,989 1 0.88275 0.43352 0.0295 1 Inch of Mercury (Hg in) 3,386 1.13282 1 0.4911 0.03342 1 Pound per square inch (lb(m2) 6,894.757 2.30671 2.03625 1 0.068046 1 Aonosphere (attn) 101,325 33.89945 29.92471 14.69595 1 1 Pa = 1 Nfm2 = 10 dyne/cm2. M-2 MEASUREMENT CONVERSIONS-Continued Unit 1 U.S. gallon per minute (gal/min) 1 Cubic foot per second (ft3fs) 1 Million U.S. gallons per day (Mgal/d) 1 Cubic meter per second (m3 /s) RATE OF FLOW gal/min 1 448.8 694.4 15,850 1 U.S. gallon per minute for 1 year= 1.614 acre-ft. 1 ft.3/s = 1.98 acre-ft/d = 724 acre-ft/yr. TEMPERATURE Unit ftlfs 0.00223 1 1.547 35.31 K Mgal/d 0.00144 0.6463 1 22.82 x degrees Fahrenheit COF) x degrees Celsius CO C) X CSt9>Cx-32) CSt9>Cx + 459.67) x Kelvins (K) x degrees Rankine COR) Cl!s)x + 32 Cl!s)x-459.67 x-459.67 X X+ 273.15 x-273.15 x (5f9)(x-491.67) CS/9)x *TURBINE SPECIFIC SPEED (Ns) Ns (U.S. customary units) Ns (Mettic hp units) N3 (kilowatt units) 1 Mettic horsepower = 75 kg-m/s nJ>l/2 N 3 = Turbine specific speed = }{5/4 where: n = rotational speed. in rpm. 1 4.45 3.81 P = power output of turbine, and H = hydraulic head on turbine. Ns (Metric hp) Ns (kW) 0.225 1 0.86 0.263 1.16 1 ml/s 6.31x10-5 0.02832 0.0438 1 x+ 459.67 Cl!5)x + 491.67 Cl!s>x X • Specific speed is a fundamental concept used in correlating ttlrbine characteristics. It now appears in many different forms, though current efforts are directed toward a unified system of units (dimensionless form). In Chapter 2, "Hydraulic Twbines and Related Topics" (Conventional, Division II, Part C), the various formulations and conversion factors are addressed. M-3 MEASUREMENT CONVERSIONS-Continued VELOCITY Unit ftld kmlh tl/s 1 Foot per day (ft/d) 1 1.27x10-5 1.157x1Q-5 1 Kilometer per hour (kmlh) 78.740 1 0.9113 1 Foot per second (ft/s) 86.400 1.097 1 1 Mile per hour (mi./h) 126.700 1.609 1.467 1 Meter per second (m/s) 283,500 3.600 3.281 VOLUME Unit L gal 1 Liter (L) 1 0.264 1 U.S. gallon (gal) 3.785 1 1 Cubic foot (ft3) 28.317 7.48 1 Cubic meter (m3) 1000 264 1 Acre-ft (acre-ft) 1,233,500 325,851 1 U.S. gallon= 231 in3 = 0.83 Imperial gallons. 1 L = 1,000 cm3 = 1.05 quans = 1,000 grams of water. 1 Barrel= 42 U.S. gallons. 1 ft3 of water= 62.4 lb. ft3 0.035 0.134 1 35.315 43,560 SI PREFIXES AND SYMBOLS Multiplication factor Prefix 1 ,000,000,000,000.000,000 = 1Ql8 exa 1,000.000,000,000,000 = 1015 peta 1,000,000,000,000 = 1Q12 tera 1,000,000,000 = 1Q9 gig a 1,000,000 = 106 mega 1,000 = 103 kilo 100 = 102 hecto 10 = 1Q1 deka 0.1 = 1Q-l deci 0.01 = IQ-2 centi 0.001 = I0-3 milli 0.000.001 =1()-6 micro 0.000,000,001 = 10-9 nano 0.000,000,000,001 = I0-12 pi co 0.000,000,000,000,001 = 1Q-15 femto 0.000.000.000000,000,001 = 10-18 atto M-4 milh 7.891x1Q-6 0.6214 0.6818 1 2.237 m3 0.001 0.00379 0.02832 1 1,233.48 Symbol E p T G M k h da d c m J.1 n p f a rnls 3.528x1Q-6 0.2778 0.3048 0.447 1 acre-ft 8.11x1o-7 3.07x1Q-6 2.30x1Q-5 8.1lx1Q-4 1 ABBREVIATIONS AND SYMBOLS ac Alternating current (adj. & noun) H Head A Ampere Hz Henz Ah Ampere hour hp Horsepower et al. And others h Hour app. Appendix Hydro Hydroelectric power avg. Average pH Hydrogen-ion concentration AVR Automatic voltage regulator in Inch bbl Barrel IDF Inflow design flood B/C Benefit-cost ratio i.d. Inside diameter BEP Best efficiency point J Joule cal Calorie Ca Cauchy number kV Kilovolt em Centimeter kVA Kilovolt-ampere ch. Chapter kW Kilowatt ft3/min Cubic foot per minute (also cfm) kWh Kilowatt-hour ft3/s Cubic foot per second (also cfs) CH Conventional hydro L Liter oc Degree Celsius max. Maximum Of Degree Fahrenheit M.H.W.L. Maximum high water level de Direct current (adj. & noun) M.W.S. Maximum water surface D.O. Dissolved oxygen MW Megawatt DOB Dynamic operating benefit MWh Megawatt-hour dyn Dyne m Meter Mgal/d Million gallons per day ed. Edition mi Mile EL Elevation csn mi/h Mile per hour (also mph) El. Elevation (in-lb) min. Minimum E" Euler number min Minute (time) F.S. Factor of safety NPSH Net positive suction bead fig. Figure N Newton Q Flow No. Number ft Foot # Number (for reinforcing bar sizes) ft-lb Foot-pound e.g. For example n Otun Fr Froude number O&M Operation and maintenance oz Ounce (avoirdupois} gal Gallon o.d. Outside diameter g Gram g Gravitational constant p. Page pp. Pages AS-I ppm Parts per million ASCE American Society of Civil Engineers % Percent ASTM American Society for Testing and PVC Polyvinal chloride Materials lb Pound AS 'ME American Society of Mechanical lbf Pound-force Engineers p Power AWWA American Water Worlcs Association PH Powerhouse ANL Argonne National Laboratories PRV Pressure reducing value BPA Bonneville Power Authority PMF Probable maximum flood BLM Bureau of Land Management PMP Probable maximum precipitation BOM Bureau of Mines PS Pumped storage USBR Bureau of Reclamation (Water and PSP Pumped storage plant Power Resources Service) PSPH Pumped storage powerhouse DOE DepruromentofEne~ USDI Depruroment of the Interior Re Reynolds number EEl Edison Electric Institute rpm Revolution per minute (also rev/min) EPA Environmental Protection Agency rps Revolution per second (also rev/s) EPRI Electric Power Research Institute FERC Federal Ene~ Regulatory s Second (time) Commission SSR Sequential streamflow routing HEC Hydrologic Engineering Center sp. gr. Specific gravity I COLD International Congress on Large Dams Ns Specific speed (turbine) IEEE Institute of Electrical and Electronic 1] System efficiency Engineers NEPA National Environmental Policy Act i.e. That is NWS National Weather Service kip Thousand pounds NERC North American Electric Reliability T.B.M. Turning bench mark Council NRC Nuclear Regulatory Commission UGPH Underground powerhouse PVC Public Utility Commission (state) PURPA Public Utility Regulatory Policies Act vs. Versus REA Rural Electrification Association vert. Vertical scs Soil Conservation Service v Volt TVA Tennessee Valley Authority VA Volt ampere COE U.S. Army Corps of Engineers USC OLD U.S. Congress on Large Dams w Watt FWS U.S. Fish and Wildlife Service we Weber number wt Weight a Year(SO yr Year (inAb) AS-2 VOLUME 4. SMALL-SCALE HYDRO CONTENTS DMSION I. PLANNING Chapter 1. Small-Scale Hydropower Perspectives A. Renewed interest in small-scale hydro B. Civil engineering perspectives C. References Chapter 2. Development of Level and Scope of Study Plan A. Introduction B. Reconnaissance study C. Appraisal study D. Feasibility study E. Feasibility report F. References Chapter 3. Site Evaluation A. Introduction B. Mapping C. Geotechnical studies D. Development of site layout E. Associated and joint-use facilities Chapter 4. Hydrologic Data A. Introduction B. Streamflow records C. Reservoir characteristics D. Tailwater rating curve E. Spillway adequacy F. Sedimentation load G. Water quality studies H. References Chapter S. Estimating Plant Capacity and Energy Output A. Data requirements and sources B. Technical characteristics of generating units C. Typical overall plant efficiency D. Row-duration method E. Detennining installed capacity and energy output using the flow-duration method F. Dependable capacity G. Storage operation and sequential analysis Chapter 6. Power System Use and Connection Requirements A. Introduction B. Need for power C. Power marketing D. Power sytem connection requirements ASCE/EPRI Guides 1989 DIVISION I. PLANNING -Continued Chapter 7. Operation and Maintenance A. Introduction B. Design phase C. Operation phase D. Operator's manual E. Description of project F. Starting the plant G. Running the plant H. Stopping the plant I. Routine maintenance J. Emergency or "need for assistance" procedures K. Revisions L. Maintenance manual M. References Chapter G.. Environmental Mitigation and Facility Design A. Introduction B. 1m pacts on fish C. Temperature and water supply considerations D. Dissolved oxygen E. flow requirements F. Gas bubble disease G. Monitoring requirements H. Dredging I. Water level fluctuations J. Aquatic plants, insects, and wildlife K. Gravel recruioneru L. References Chapter 9. Institutional Issues A. FERC licensing B. Consultation process C. Legislation relevant to small-scale hydro development D. Cumulative impacts E. Reference Chapter 10. Project Schedule A. Introduction B. Preliminary planning C. Regulatory issues D. Design and construction Chapter 11. Cost estimates A. Introduction B. Screening tools C. Reliable cost estimates D. References ASCE/EPRI Guides 1989 DIVISION I. PLANNING-Continued Chapter 12. Economic Analysis A. Introduction B. Costs C. Benefits D. Economic assessment E. Optimizing plant size using approximate economic methods DIVISION II. DESIGN Chapter 1. Storage, Diversion, and Appurtenant Structures A. Defmition and type B. Field data requirements C. Design of storage and diversion structures D. Material specifications E. Spillways F. Low-level outlets G. Sedirnemt control H. River diversion during construction I. References Chapter 2. Waterways A. General design concepts B. Intake structures C. Power canals D. Penstocks and conduits E. Tailrace channels F. Hydraulic modeling G. Downstream fish passage H. Upstream fish passage I. Instream fishery mitigation and habitat improvement J. References Chapter 3. Power Plants A. Conceptual studies B. Powerhouse types C. Powerhouse layout D. Powerhouse size E. Superstructure F. Substructure arrangement G. Thrbine setting H. Excavation I. Structural requirements and analysis J. Structural stability requirements K. Hydraulic requirements L. Powerhouse equipment M. Auxiliary electric equipment N. Auxiliary mechanical equipment ASCE/EPRI Guides 1989 DIVISION II. DESIGN -Continued 0. Esthetics P. References Chapter 4. Substations and Transmission Lines A. Substations B. Transmission lines DIVISION ill. CONSTRUCTION Chapter 1. Construction Contracts Chapter 2. Acceptance Tests A. Standard test procedures ASCE/EPRI Guides 1989 The "Planning" division was written by: Thomas G. Gebhard, P.E. Gebhard Engineers 5750 Balcones Dr., Suite 210 Austin, Texas 78731 Chairman, Small-Scale Hydro Committee Garith Grinnell, P.E. Stone and Webster Engineering Corp. P.O. Box 5406 Denver, Colorado 80217 Charles E. Bohac, Ph.D., P.E. Tennessee Valley Authority 2S 270C Haney Building Chattanooga, Tennessee 37401 Richard T. Hunt, P.E. Consultant 16 Kensington Road. Concord, New Hampshire 03321 Ray Toney, P.E. Ray Toney and Associates P.O. Box 1342 Redding, California 96099 Ronald F. Ott, Ph.D., P.E. Ott Water Engineers 1412 I 40th Pl., N.E. Bellevue, Washington, 98007 SMALL-SCALE HYDRO DIVISION I. PLANNING Chapter 1. Chapter 2. Chapter 3. Chapter 4. Chapter 5. Chapter 6. Chapter 7. Chapter 8. Chapter 9. Chapter 10. Chapter 11. Chapter 12. Smaii·Scale Hydropower Perspectives Development of Level and Scope of Study Plan Site Evaluation Hydrologic Data Estimating Plant Capacity and Power Output Power System Use and Connection Requirements Operation and Maintenance Environmental Issues Institutional Issues Project Schedule Cost Estimates Economic Analysis ASCE/EPRI Guides 1989 CHAPTER 1. SMALL-SCALE HYDROPOWER PERSPECTIVES CONTENTS Section Page A. Renewed interest in small-scale hydro ........................................................................................................ I-I 1. Introduction ............................................................................................................................................. 1-1 2. History .................................................................................................................................................... 1-1 3. Other small-scale hydro guides and technical references ....................................................................... l-2 4. Objectives of these guidelines ................................................................................................................ l-3 5. Distinctive features of small-scale hydro ................................................................................................ l-3 6. Small-scale hydro perspectives ............................................................................................................... l-4 B. Civil engineering perspectives .................................................................................................................... l-4 1. Planning .................................................................................................................................................. 1-4 2. Design ..................................................................................................................................................... 1-5 a Elements ............................................................................................................................................. 1-5 b. Constraints .......................................................................................................................................... l-5 c. Considerations .................................................................................................................................... 1-6 d. Comments ........................................................................................................................................... 1-6 3. Project implementation ........................................................................................................................... 1-7 C. References ................................................................................................................................................... l-8 ASCEJEPRI Guides 1989 CHAPTER 1. SMALL-SCALE HYDROPOWER PERSPECTIVES A. RENEWED INTEREST IN SMALL-SCALE HYDRO 1. Introduction The Small-Scale Hydro Guidelines are intended for use in conjunction with the Guideline Conventional Hydro Guidelines also published by ASCE/EPRI in 1989. They have been intent developed to give civil engineers insight into the problems and solutions of small hydro projects based on previous engineering experience. The following definitions describe hydroelectric projects: Conventional: > 15 MW Small-scale: 1 MW to 15 MW Mini: 100 kW to 1 MW Micro: < 100 kW Small-scale, or small, hydro encompasses a broad range of capacities, heads, and flows, and the total project capacity may not fall into the strict range of small hydro defined above. The reader is left to determine whether a project with &-5 MW units falls in the cat- egory of small or conventional hydro, and to what degree concepts presented in these Small-Scale Hydro Guidelines should be applied to a 40-MW project. Many fields of expertise are required to accomplish a successful small hydro project. This document does not cover them all. Nor does it represent a final guide to the practice of developing small hydro. 1be many contributors to this work hope that this document will serve as a working reference for civil engineers as they pursue the development of the small hydro resource in the United States. 2. History In the history of hydro development in the United States, small-scale hydropower has the unique position as the source of the conventional, pumped storage, and tidal power tech- nologies. Since the advent of the first tumine-generator to convert water to electricity at Appleton, Wisconsin, in 1880, the hydro field has expanded to harness much of the hydropower of the United States that can be developed economically. With the mega project era coming to a close (large projects developed by the Bureau of Reclamation, Corps of Engineers, and major public and private power companies) the small-scale hydro project reemerged during the oil crisis of the early 1970s. National policy encouraged new development, restoration of old sites that had been decommissioned or abandoned because of economics, and development at existing dams where previous studies indicated development was not economical. Small hydro features Historical National policy 1-1 ASCE/EPRI Guides 1989 3. Other Small-Scale Hydro Guides and Technical References The renewed focus on small hydro has produced several documents that provide guidance on the planning and design of small-scale hydro developments. These documents are listed and described below. Where appropriate, material presented in these documents was used in these ASCEIEPRI Guidelines. Each of the documents below had specific objectives, just as the Guidelines is intended for use by civil engineers. • COE, U.S. Anny Corps of Engineers, Hydropower Cost Estimating Manual, June 1979. Provides procedures for preparing reconnaissance-level cost estimates for sin- gle-purpose power projects. The report provides cost data for dams, spillways, intakes and outlets, powemouses, waterways, land purchase, reservoirs, engineering, over- head, interest during construction, and annual capital and operating costs. • COE, Feasibility Studies for Small-Scale Hydropower Additions-A Guide Manual, July 1979. A manual devoted exclusively to the addition of generating facilities to an existing facility for completeness; it does contain material on dams, etc. The manual covers hydrology, concepts and layouts, power marketing, project evaluation, envi- ronmental and legal, project sizing, powemouse arrangements, cost data, switchyards and transmission. • USDI, Department of the Interior, Reconnaissance Evaluation of Small, Low-Head Hydroelectric Installations. Assesses small hydro additions at existing facilities. Screens 159 sites in the range of up to 20 meters head and 15-MW capacity. Project elements covered are penstocks, power facilities, transmission, and other costs. • EPRI, Electric Power Research Institute, Simplified Methodology for Economic Screening of Potential Low-Head, Small-Capacity Hydroelectric Sites, Tudor Engineering, January 1980. A clear, well-written, concise document that presents use- ful cost data. • Noyes, R., Small and Micro Hydroelectric Power Plants, Technology and Feasibility, 1980. This document is a well-edited version of the Corps of Engineers manual, Feasibility Studies for Small-Scale Hydropower Additions -A Guide Manual. • McKinney et al., Microhydropower Handbook, 2 vols., U.S. Department of Energy, January 1983. A basic manual for very small hydro applications. • Farag, E., Canadian Electrical Association, Methodology for the Design and Costing of Small Hydro Plants, Shawinigan Consultants. A well-written, useful manual that facilitates the design and costing of small-scale hydroplants. • Warnick, C.C., Hydropower Engineering, Prentice-Hall, Inc., 1984. Although it is not a hydro guide, this recent addition to the literature should be especially useful to engi- neers on small hydro projects. ASCEJEPRI Guides 1989 1-2 Continuing Sources of Reference: • Hydro Review. A magazine that covers the American hydropower industry. • Water Power and Dam Construction. A magazine that covers worldwide hydro devel- opment. • Waterpower conferences. Held every two years at selected cities in the United States. • International symposiums on small-scale hydro. Held about every two years. 4. Objectives of These Guidelines These guidelines provide civil engineers with infonnation on the steps important in plan- ning and designing small-scale hydro projects and assist users in focusing on the essential elements that are often treated too lightly in the early stages of development This document has been developed by civil engineers for use by civil engineers. It does not cover some of the fundamental teclmical aspects of small hydro development, which are presented in other guides. It does not address electrical, mechanical, environmental, geoteclmical and construction to a degree commensurate with their importance to the total development of a project. However, these guidelines do address those areas in related dis- ciplines where practice and experience have shown that inadequate attention by the civil engineer has created project difficulties and can be fatal to a project development plan. S. Distinctive Features of Small-Scale Hydro The Small-Scale Hydro Guidelines focus on and emphasize the differences between con- ventional hydro projects and small hydro projects. Common elements and teclmical detail are contained in the Conventional Hydro Guidelines and are referenced where appropriate. A further distinction is the difference between rehabilitation, expansion, and new facilities. Rehabilitation of existing facilities (either functioning or decommissioned) is usually con- trolled by very definite space and size requirements that are not easily changed. Hydraulic and equipment limitations are usually the most affected areas. Innovative solutions are often needed in these circumstances to make redevelopment possible. Recent equipment and control improvements resulting from extensive use of computers have improved the efficiency and output of small hydroplants that might, otherwise, be faced with hydraulic restrictions. Existing dams offer the opportunity to design some new facilities with modem teclmiques, but may also have some restrictions, such as existing penstock/outlet facilities. Application of siphon units, submersible units, and pumps running as turbines are applications of cre- ative designs that have been used. Entirely new facilities have the nonnal design restric- tions typical of any new development; cost is the most critical restriction. Finally, the differences between U.S. and foreign practice should be mentioned. Probably the most significant difference is the relatively few isolated small hydro systems in the Objectives Rehabilitation U.S. vs. foreign practice 1-3 ASCE/EPRI Guides 1989 Small vs. conventional Design focus Planning Basic elements of small hydro United States. For recent developments, the U.S. practice of connecting to the existing util- ity system is almost assumed because the sale of power is critical to the project economics. On the other hand, foreign developments particularly in less industrialized areas, present many opportunities for stand-alone systems. Justification of the project may involve the determination of secondary benefits and even national or political considerations. These Guidelines focus primarily on U.S. practice. 6. Small-Scale Hydro Perspectives These Small-Scale Hydropower Guidelines differ from the Conventional Guidelines in that they focus on the planning aspects of projects. The transition of technology from conven- tional is simply to the smaller. However, the impact of the normal process going from ini- tial ideas to operating project is much more critical with small projects because the capital cost and expected revenues are relatively small. There is less ability for changing or refm- ing project elements at the later stages of the project because of the tighter budgets. The elimination of surprises or unnecessary expenditures is the goal of the planning phase of small hydro projects. It is therefore necessary to go beyond the usual planning levels customary for conventional hydro to ensure that all areas of project development, including technical, economic, financial, environmental, and institutional, do not contain fatal flaws that would stop the project A common pitfall is to relate small hydro with fewer problems or concerns. It is true they may be smaller in size, but the time and money available to resolve them is even smaller. Therefore, the proper evaluation of all project elements, even to operation and maintenance considerations, must be adequately addressed during the planning phase of the project The design section of these Small-Scale Hydro Guidelines (division D) focuses on the ele- ments of small hydro projects that are unique and different from those of conventional hydro practice. The importance of using shelf items rather than custom-built items is a high priority to help reduce costs. In contrast to conventional hydro where construction costs greatly exceed engineering costs, large savings may be possible during construction by expenditure of nominal engineering funds. In small hydro, this process of optimizing con- struction costs may be considered an unaffordable luxury. The iterative refmements from conceptual plan to final design can seldom be afforded. A once-through design process is preferred whenever possible. B. CIVIL ENGINEERING PERSPECTIVES 1. Planning The elements of planning which govern small hydro developments are the economics, power marketing and project financing. Without workable solutions to these three areas, the technical, environmental and institutional considerations are of little consequence. This is not to say that the environmental, licensing or engineering elements of small hydro are without challenges and are to be taken for granted. Rather, it is important for engineers to recognize that early in the planning stage financing, marketing and economics must be evaluated to determine whether the project can proceed into conceptual design and licens- ASCEIEPRI Guides 1989 1-4 ing. The design of a project without a power marlcet is of little use to anyone. A project without fmancing ceases to be an active project Early and continual evaluation of these elements through project planning will help to identify at an early stage the viability of the project The civil engineer likes to consider the technical and environmental issues important, par- ticularly as they are required by licensing and pennitting procedures. There is no question that they are basic to any hydro development. and cannot be neglected. However, since the small hydro project is often developed by organizations other than power utilities, who typ- ically provide their own economic analysis, power marketing and project fmancing, these elements of the planning process should be kept in the forefront by civil engineers involved in project development. 2. Design a. Ekments.-The elements of design covered in these guidelines address the following areas: • Dams and diversion structures • Spillways and outlets • Penstocks and waterways • Power plants • Substations and transmission lines Only those items unique to hydro applications on small-scale projects are covered. As a result, the depth and detail of infonnation presented is a function of the applicability of conventional hydro practice and the amount of current infonnation available in the litera- ture. Design Elements b. Constraints.-A 1985 EPRI report contains the following statement: "A key conclu-Constraints sion from the small hydropower program was that environmental, regulatory, power mar- keting, and financial factors are the major constraints to small hydro development rather than technical factors." Although this important facet of small hydro is clear, it does not lessen the fact that small hydro developments that have low capital and operating costs and high availability (technically sound projects) are more likely to be economically justified and that proper engineering and adherence to good hydroelectric design practice is essential. Most important technical considerations depend on the site characteristics, however, the key feature in the design and operation which will establish the worldng arrangements of all other elements will usually be the turbine. While energy values may be low indicating efficiency and other losses may not be critical, the technical operation of the turbine is always of great importance. It must operate reasonably free of maintenance, cavitation, vibration, and surging. Fundamental to small hydro engineering is the fmding of cost-effective solutions that will Cost-effective allow development of sites that were uneconomical before the 1972 oil embargo (low-head solutions and/or small-capacity). One might almost consider this the engineering challenge to small hydro development 1-5 ASCE!EPRI Guides 1989 Considerations Comments c. Considerations. -During feasibility studies, proper attention to the considerations list- ed below play a key role in establishing the concepts for structural design. For small hydro the luxury of design optimization may not be affordable. It is well to establish the design relationships and stick to them because neither time nor money may be available to change them. • Appropriate project alternative layouts • Arrangement of the features • Turbine setting and power plant location • Penstock alignment and velocities • Operating criteria for power plant • Need and location of surge tanks • Dimensions of hydraulic structures and outlet • Intake location and geometry • Plant size, machine type and number • Modeling needs • Tailrace geometry and excavation • Outlets, diversions, spillways, canals, reservoir studies • Field data requirements • Economic viability of the project d. Comments. -Some comments on engineering problems present at small-scale hydro projects are listed below. • Hydraulics problems at small hydro projects are likely to be more complex than con- ventional projects. It can prove difficult to add a hydroelectric plant to an existing project since the original layouts and operation were not predicated on its existence. Past experience and successful solutions should be consulted as guides. Difficult intake, submergence, and turbine installation problems have all been addressed at previous projects and acceptable solutions found. [Waterpower '79, '81, '83, '85, '87]. • Low head and small capacity increase a project's capital costs, whereas low energy benefits reduce its economic viability. • Consider turbines installed on existing outlet work:s as an example of a typical small hydro technical problem. Such outlets are usually designed without a water hammer allowance, but now must accommodate the uncontrolled operation of a turbine which can produce substantial pressure variations. • Inability to pierce a structure with a penstock or other conduit can immediately void an otherwise economically viable project. • Existing hydraulic arrangements such as spillways and outlets may not be compatible with the proposed power plant • Power projects on canals presents unique hydraulic and construction problems. • Siphon intakes to low head existing projects have solved some difficult project prob- lems. • If a new dam or diversion structure is required, economic and environmental con- straints may prevent development • Fish bypasses and turbine mortality need consideration. • Storage and pondage add valuable benefits to the project energy values, but often are not obtainable. ASCE/EPRI Guides 1989 1-6 • Transient analysis is less important at a small-scale hydro project • The addition of hydro at an existing navigation lock may require modelling the tailrace. 3. Project Implementation Basic to the orderly process of project planning and development is the project schedule. It is the guide to estimating the potential for project success, and for measuring progress as the project proceeds. It helps to identify areas of critical concern to project progress as well as the independent and interdependent tasks. Knowledge of some elements affecting the project schedule may be unfamiliar to the young civil engineer. Such areas as financing, permitting, environmental review procedures, mechanical, electrical, and control elements of the project should be discussed with professionals in these areas of expertise to obtain realistic schedule requirements. While it is anticipated that during the course of any project, some modifications to the schedule are expected, it must be recognized that a poorly developed schedule will impact the project costs. In an extreme case, this can compromise the completion of the project by directing work effort to areas out of sequence and expending funds unnecessarily. Inefficiency of some work effort on a large project may be easily recovered, but on small hydro projects a poorly developed schedule can kill an otherwise good project. Because of the relatively small construction effort required on most small hydro projects, it is normally expected that the project will be completed in one year or less. The critical issue that will affect the construction effort is the availability of material and equipment at the site when needed. Construction costs can soar if delays are caused by equipment sup- pliers. On small hydro projects it is best to limit the number of equipment suppliers. A sin- gle turbine-generator package may be the only supplier if the general contractor supplies all other equipment. If the project requires a large or long penstock, consideration should be given to a separate contract because of the long lead time required for fabrication and delivery. Design simplicity is the key to a cost effective small hydro project. Local contractors are usually capable of constructing these projects, but are not experienced in technically com- plicated construction techniques. Their costs will be very competitive due to their local presence and therefore to take best advantage of this resource, designs and materials should reflect the locale wherever possible. Consideration of the operation and maintenance (O&M) requirements of a small hydro project cannot be put off until construction is completed. They must not be an afterthought since the cost of O&M is critical to the economic viability of the project For example, if it is desired that an unattended plant remain shut down after a trip out, until an operator man- ually restarts the unit, the time to accomplish this action must be considered. If it would take days rather than a few minutes to restart the unit, the cost of lost revenue must be con- sidered in addition to the manpower costs. In some circumstances, remote startup capabili- ty may be more cost effective. These considerations should be thoroughly evaluated in the planning and design of the project so that costly changes after construction begins are avoided. Schedule Results of poor schedule Construction Equipment contracts Use of local contractors Operation and maintenance Operation philosophy 1-7 ASCEIEPRI Guides 1989 Maintenance requirements Maintenance shortcuts may be costly Maintenance requirements should be established early in the design phase so that manpow- er and material requirements are understood and properly accounted for in the project eco- nomics. Maintenance schedules must be established and specified for the equipment pur- chased, to avoid daily maintenance chores for a maintenance crew scheduled to appear only once a week. The cost of regularly scheduled maintenance should not be considered a means to improve project economics. Shortcuts with required maintenance will soon result in major equipment problems that will not only prove costly but also result in lost revenue. C. REFERENCES See Section A.3, "Other Small-Scale Hydro Guides and Technical References." ASCEIEPRI Guides 1989 1-8 CHAPTER 2. DEVELOPMENT OF LEVEL AND SCOPE OF STUDY PLAN CONTENTS Section Page A. Introduction ................................................................................................................................................. 2-1 B. Reconnaissance study .................................................................................................................................. 2-2 C. Appraisal study ............................................................................................................................................ 2-2 D. Feasibility study .......................................................................................................................................... 2-4 E. Feasibility report ......................................................................................................................................... 2-4 1. Outline .................................................................................................................................................... 2-4 2. Elements .................................................................................................................................................. 2-6 3. Common deficiencies in feasibility reports ............................................................................................ 2-7 F. References ................................................................................................................................................... 2-8 FIGURES Figure 2-1 Reconnaissance study components ........................................................................................................ 2-3 2-2 Project fonnulation components-feasibility ...................................................................................... 2-5 ASCE/EPRI Guides 1989 CHAPTER 2. DEVELOPMENT OF LEVEL AND SCOPE OF STUDY PLAN A. INTRODUCTION The planning process for the development of small-scale hydropower is typically based upon a series of studies that describe the project in greater detail. Planning is a dynamic process that proceeds through several stages increasing the knowledge of the project development, providing answers and information on critical issues, and narrowing the focus on issues that must be resolved. At each stage, decisions must be made: primarily, whether an investment should be made in the next step of the project or the project aban- doned. The decision on whether to proceed with or abandon the project is based upon technical, economic, financial, environmental, and institutional issues. The level of plan- ning is often reflected by the needs of the owner, the size of the project, and the amount of information needed to obtain financing. Planning studies are essentially an iterative process whereby project benefits and costs are compared as the studies progress in the analysis of the project. Essentially, this sequential process assists in defining the time to abandon a project. For example, if a site does not have adequate head and flow to generate electricity with an income sufficient to retire the debt on the site, a planning study should not continue to assess environmental issues, a license application should not be filed, and design drawings should not be produced. The planning process can be regarded as a two-or three-stage process. 1be three common- ly used studies for the evaluation of non-federal developments at small hydroelectric sites are reconnaissance, appraisal, and feasibility. For the evaluation of federal developments at small hydroelectric sites, the two commonly used studies are reconnaissance and feasibili- ty. A reconnaissance study determines (1) the technical feasibility of a project, (2) critical issues that must be resolved before proceeding with the project. and (3) the first economic evaluation of the project feasibility. An appraisal study provides the technical, economic, and fiscal data necessary to (1) obtain financing for the development and (2) file a license application with the Federal Energy Regulatory Commission (FERC). A feasibility study provides all information necessary to make the decision on whether to design and construct a project. On small hydroelectric projects, the three stages can be obscured in the continuum of the planning process. On potential projects less than 1 or 2 MW, it is not uncommon to make a decision to proceed to licensing, design, and construction on the basis of a brief reconnais- sance study. It is also not uncommon to begin a study at the request of a developer and pro- ceed to the end of the feasibility process while supplying only oral or letter reconnaissance and appraisal reports. Potential projects larger than 5 MW assume more formal definitions of the planning process. Each type of study has a table of contents generally accepted by most users of planning studies. However, if a study is conducted by beginning with the first section and sequential- ly progressing to the last section, the engineer will miss the iterative nature of the planning process; that is, the focus upon the continual comparison of project benefits and costs. Studies Decision to proceed Iterative process Stages Project benefits vs. costs 2-1 ASCEIEPRI Guides 1989 Economic evaluation Items of reconnaissance study Appraisal study B. RECONNAISSANCE STUDY The reconnaissance study has the objective of defining whether further study is warranted, and is designed to reduce the chance of a subsequent unfavorable feasibility finding. During the reconnaissance stage, the technical feasibility of the project and the use of the power is defined and quantified to make a preliminary economic evaluation of the project. The reconnaissance study as defined by the Corps of Engineers generally includes the fol- lowing items: • Define power potential • Estimate power output • Assess market potential • Identify physical works needed • Develop project hydrology and hydraulics • Formulate and cost project • Adopt power values • Develop power benefit stream • Determine economic feasibility • Identify critical issues, i.e. environmental and social • Assess legal/institutional issues • Assess site issues • Assess facility integrity • Assess fmancial issues • Document findings For the nonfederal developer, the reconnaissance study often omits many of the fmancial related issues and concentrates primarily on technical feasibility. The iterative process of a typical reconnaissance study is shown on figure 2-1. C. APPRAISAL STUDY The purpose of the appraisal study is to provide the financial and economic data necessary to attract capital to the project and to develop the information required for a license appli- cation to FERC. The appraisal study is primarily for the non-federal developer and contains the detailed financial studies not performed in the reconnaissance study as well as any additional infor- mation needed by the project's investors or bankers. ASCE/EPRI Guides 1989 2-2 ~ )>- (/) ~ ~ 2 5~ (1) Vl ,_. "' 00 "' et•llu tllaCIPlL lilaC Ill I.(WIIff CIIIICil !lUll I 11o1 ::m~~~~::~~ I .. 1 IIIU I lltrl ... u fllltll GIVElO" , .. , . IUIHtf UlfU 0(Vfl0t tOll ....... Figure 2-1.-Reconnaissance study components. [Noyes, 1980]. "'""'"' UCON"A1 SUNCf fiNOINU Three-part process Items of feasibility study Feasibility study outline D. FEASIBILITY STUDY The feasibility study has the objective to fonnulate a feasible project and to assess its desir- ability for implementation [Noyes, 1980]. The feasibility study meets the objective through a three-part process [Cunningham, 1984}: 1. To identify the most attractive hydropower development for the site. 2. To fonnulate the development (or to present fonnulations of equally attractive alterna- tives). 3. To detennine whether or not the proposed development merits an investment commit- ment. Essentially, the feasibility study enables the developer to proceed with design and construc- tion. The feasibility study as defined by the Corps of Engineers generally includes more infonna- tion on the items listed above for the reconnaissance study as well as the following items: • Fonnulate power features • Refine power output estimates • Recompute the benefit streams • Cost project power features • Select project power features • Perfonn sequential power routing • Refine power features and perfonnance characteristics • Complete project benefit cost analysis • Assess financial requirements • Application for licenses and pennits • Environmental factors require continuous evaluation at all study levels The iterative process of a typical feasibility study is shown on figure 2-2 [Noyes, 1980}. E. FEASIBILITY REPORT 1. Outline The generally accepted outline for the feasibility study report is as follows: Chapter I. II. III IV. v. VI. VII. VIII. IX. Title Summary Introductory Material Site Characteristics and Existing Facilities Hydrology and Sediment Alternatives and Recommended Project Development Hydraulics of Recommended Development Project Power Production Environmental, Social, and Institutional Impacts Project Costs ASCEIEPRI Guides 1989 2-4 / / / r---, "' •• I / !=5: I / 1 ·:t: v"' I ;•a• I I :sa: I '---.J r---, ' I I I ~-M I I -:; I I :~e '( ' ::: 1 L_::j r---r:::;1 I .: I ==== I I ::::: 1 :-;: I _... t~! I ;;::~;~ I / 1 e:· I ::~! I / L l'lo f "'!::~=I .--.... ...., ___ ...... .:.,._...,~ ........ .... _ .... _ r--:.-, I ! I I .; I I ;~ I l :: I I :; I ...._-_...~ ,....-....., .... _-,--, -........ I .._ I I I I I . . 2-5 .. .. . ' ' .... _i ~ : I -I .a, .. u --.... ;;; -... ·--::~"'• =i L--..J ', r---, \ \ \ ' I :;t:l I 'I ::..,. I , =:: 1 I ••• :!.. I I I \ \ \ \ '---....1 \ \ \ r---, ' 1 iiI ..J ::i:: I 1 :•c• t I : i t I .. " '----J r~--, 'i i : .. I I : .. :::I I _,.~_. ::: .. I I~-:! I I ...... I l.E--...J ASCE/EPRI Guides 1989 Elements of feasibility study X. Marketing Considerations XI. Economic Evaluation XII. Financial Analysis XIII. Project Implementation XIV. Conclusions and Recommendations 2. Elements Within the overall outline of the feasibility study, various elements should be provided to adequately describe the nature and depth of studies that were conducted. The report should not be too technical in nature so as to confuse or lose the reader, but it should not be too general either, so as to invite misinterpretation. The elements that should be included in the feasibility report are listed and described below [Cunningham, 1984]: • Summary and introductory materials. Identifies essential features of the study; his- tory and general description of the project; operational and development costs; esti- mates of energy generation; discussion of important alternatives; mention of unusual or special conditions. The scope of the study is defmed in terms of what it intends to do and not to do. • Site characteristics and existing facilities. Includes complete description of the exist- ing site and facilities; geographic location and relationship to the surrounding area; purpose for which the facilities were built; information related to legal access and ownership of the site and facilities, including water rights; geological characteristics of the site; potential problems of hazards; evaluation of existing structures that will be included in the project; relative historical data. • Hydrology and hydraulics. Describes features and characteristics of the site and drainage basin that affect the flow of water at the site; identifies sources and methods used in developing the hydrological and hydraulic characteristics: description of the watershed; evaporation, precipitation, and stream gauge data; upstream diversions of water regulation that affect flow; flow duration curves and related flow data, including the results of any flood studies; headwater and tailwater rating curves and expected head losses through water passageways. The accuracy and completeness of the hydraulic data is crucial, especially when evaluating low-and ultra-low-head sites. • Project development. Describes the recommended development; includes all facili- ties and aspects of the site or institutional considerations that have significantly influ- enced its size, configuration, or mode of operation; presents assumptions made; and discusses alternatives. • Power production. Presents documented estimates of the average monthly and annual energy generation; includes expected variations in wet and dry years; estimates both firm and nonfirm capacity: states headlosses, equipment efficiency data, and other parameters used in the energy studies. ASCEIEPRI Guides 1989 2-6 • Project costs. Includes capital costs (construction, environmental impact mitigation, land, and indirect costs of engineering, legal services, management, fmancing, and interest during construction and annual costs) debt service, operation and mainte· nance, administrative costs, and taxes. The method used to estimate costs should be completely explained, including the basis used to escalate costs for future years. • Financing alternatives and energy costs. Includes complete investigation of avail- able financing alternatives; considers the cost of financing, rate of interest, the repay- ment period, total annual debt service, and escalation of annual operating costs in future years. • Marketing considerations. Describes and evaluates potential markets for the sale of energy; estimates present and future value of energy; considers applicable govern- ment regulations or laws that affect energy marketability or value; and detennines reasonable value for energy to be used as basis for evaluating economic and financial viability of the project. • Economic evaluation. Detennines overall economic feasibility of the project; com- pares anticipated benefits with the costs over its economic life; includes benefit cost ratios, net present worth, internal rate of return, cash flow projections, escalation rates, and discount rates. • Environmental and related concerns. Assesses effects on the existing natural envi- ronmental and on socio-institutional aspects of its development (e.g. employment, recreation, etc.); reflects the impact of working knowledge of applicable government regulations as they relate to water quality, changes in stream flow, effects on wildlife, and effects on sites of historic or archaeological value; and describes necessary miti- gation measures. • Project implementation. For projects found to be feasible or marginally feasible, this section discusses steps required to bring the project on line; identifies all necessary local, state, and federal pennits and licenses as well as appropriate government agencies that must be consulted; presents a plan that explains the time and cost required to accomplish the discrete stages of the project; and discusses any unusual or special considerations affecting the development along with a plan of how to mitigate them. 3. Common Deficiencies in Feasibility Reports Based upon an analysis of 265 feasibility studies for small hydroelectric projects, Cunningham [1984] reported the following common repon deficiencies: • Annual energy generation. Estimates for energy production were unrealistically high because of (1) improper use of headwater and tail water curves or the use of constant gross head during a broad range of flows; (2) failure to include head losses at gates, trashracks, and draft tube; (3) failure to account for losses at speed increaser, genera- tor, and transfonner, for electrical use at the station, or for scheduled and unscheduled outages; (4) improper use of flow data representing wet or dry periods of time; and (5) failure to reduce flows for leakage, withdrawals, and environmental releases. Report deficiencies 2-7 ASCE/EPRI Guides 1989 • Cost estimates. Cost estimates were incomplete -missing such obvious costs as land acquisition, interconnection equipment, transportation and installation of equip- ment, and environmental mitigation. • Transmission and interconnection. Few studies provided information on the local utility's requirements for interconnection. Missing items included the distance of the line to interconnection, the voltage of the utility line, and the ability to accommodate the additional load on existing lines. • Environmental concerns. The environmental aspects most commonly missed includ- ed the impact on fish habitat for long sections of streambed with inadequate flows and the impact of impoundments upon quality of released flows. • Institutional concerns. Institutional concerns most commonly missed included (1) a realistic assessment of the time to complete licensing, especially when significant environmental impacts are present or when the state has strong environmental regula- tions; (2) the time needed to gain control of property and water rights, when the developer does not own the site; and (3) the failure to include time and money to obtain state and federal approval when the project affects historical structures. • Value of power and marketing. The value of power was improperly defined for the life of the project by (1) incorrectly identifying the market and the initial rate, and (2) using an overly optimistic escalation rate for the life of the project The potential mar- kets for the project's power output were not properly identified. • Project financing. 1be most frequently occurring deficiency in a feasibility study is the description of the project financing. The most commonly missed items include (1) the cost of project fmancing, (2) interest during construction, (3) escalation of project costs, (4) reserve funds and coverage, and (5) the rationale used to select interest rates or term of loans. It was common to have little or oo discussion of "negative cash flow" and its impact on the financial feasibility of a project. F. REFERENCES Noyes, R., Small and Micro Hydroelectric Power Plants, Technology, and Feasibility, 1980. Cunningham, C., "Evaluation: Feasibility Studies, A Closer Look," Hydro Review, Fall 1984. ASCE!EPRI Guides 1989 CHAPTER 3. SITE EVALUATION CONTENTS Section Page A. Introduction ................................................................................................................................................. 3--1 B. Mapping ...................................................................................................................................................... 3--1 1. General .................................................................................................................................................... 3--1 2. Data sources ............................................................................................................................................ 3--1 C. Geotechnical studies .................................................................................................................................... J--2 1. General .................................................................................................................................................... J--2 2. Review of existing data and site inspection-stage 1 ........................................................................... 3--2 a. I>esign records .................................................................................................................................... 3--2 b. Construction records ........................................................................................................................... J--2 c. Historical reservoir or river operations records .................................................................................. J--3 d. Maintenance records ........................................................................................................................... J--3 3. Subsurface exploration-stage 2 .......................................................................................................... 3--3 D. I>eveloprnent of site layout ......................................................................................................................... 3-4 1. Genera1 .................................................................................................................................................... 3-4 2. Project layout .......................................................................................................................................... 3--5 E. Associated and joint-use facilities ............................................................................................................... 3--5 1. Associated facilities ................................................................................................................................ 3--5 2. Joint-use facilities ................................................................................................................................... 3-6 ASCE/EPRI Guides 1989 CHAPTER 3. SITE EVALUATION A. INTRODUCTION The scope of investigations advisable to provide the necessary data to adequately evaluate conditions for planning a small-scale hydropower project depend primarily upon the fol- lowing: 1. Arrangement, condition, and operational requirements of existing structures and space available for new structures 2. Site topography and geology as it relates to project requirements 3. Access, construction laydown, and diversion requirements specific to the project and site For example, the time and resources required to perfonn the requisite evaluations for a small-scale hydro project involving the renovation/retrofitting of existing dam and power- house structures in visibly good condition vary considerably from those necessary to study a site where the hydro development is newly constructed and the surface configuration and appearance of the soiVrock at the anticipated location of proposed project facilities indicate the need for substantial subsurface investigation. Diversion and dewatering requirements should be evaluated because they may render a small hydro development uneconomical. This chapter describes the general infonnation and data required to evaluate a site where a small-scale hydropower project is proposed. B. MAPPING 1. General The mapping data collected should be of sufficient detail and scale to prepare documents for use in site layout. hydropower facility design, project-associated recreational facility layout and design, reservoir impact evaluation, downstream flow evaluation, power line siting and layout, FERC licensing, and future project expansion or inspection work. However, all data must be verified by field reconnaissance inspection before preparation of final maps. 2. Data Sources Numerous sources of data can aid in the preparation of project mapping. A partial list of potential sources includes: • USGS topographic quad maps • City/county topographic maps • Topographic maps prepared by highway departments that show bridges or highways in the vicinity of potential hydropower sites • FEMA flood studies of river segments (provides river gradient, selected cross-section data, and selected topographic data) Factors determining scope of investigations Mapping data required Sources of map data 3-1 ASCEIEPRI Guides 1989 Purpose of stages Stage 1 data • COE dam safety reports (available for some existing dams) • SCS county soil surveys provide some infonnation about vegetation, meteorology, demography. soil mapping, soil characteristics, geology, and local history • Regional, state, and local geologic maps • City/county development plans • City/county zoning maps • City/county tax maps • U.S. Forest Service maps • BLMmaps • Environmental, social (e.g., local barber shop) C. GEOTECHNICAL STUDIES 1. General The development of a scope for required geotechnical studies generally involves two stages of effort. The purpose of stage 1 is to make an initial evaluation of the integrity of the existing facilities, maximum use of all available records, and on-site examinations. One of the objectives of stage 1 is to detennine whether or not stage 2 is needed for a final eval- uation and to establish the scope of engineering studies for stage 2. In stage 2, supplemental data and analyses are acquired and evaluated, and conclusions are made concerning the integrity of the impoundment and any need for remedial repairs or alterations. Stage 2 testing is required if new facilities are planned. 2. Review of Existing Data and Site Inspection -Stage 1 Data such as that listed below (if available) should initially be thoroughly reviewed: 11. Design Records • Contract plans and specifications • Geologic report • Site and materials exploration report • Design report or design basis • Materials testing and appraisal report • Site seismicity report • Designer's operating criteria • Technical record of design b. Construction Records • Photographs • Inspector's reports • Record of foundation testing or grouting • Quality control test records • Construction reports • Geology reports ASCE!EPRI Guides 1989 3-2 c. Historical Reservoir or River OperaiWns Records • Stage and water level readings • Discharge records • Gate/valve/control operations d. Maintenance Records • Maintenance problems • Repairs • Alterations 3. Subsurface Exploration -Stage 2 The type of information and numerical data needed concerns structural, geologic, and per- formance features unobtainable by direct visual examination. In small hydro the cost of subsurface exploration must be balanced against the risk factors. This requires a detailed commitment on the part of the owner to understand the potential risk. The integrity of facilities may be questioned if foundation or embankment conditions are unclear or if satu- ration levels and seepage levels are important. In such cases, subsurface exploration is required to develop additional data and to provide samples for laboratory testing to deter- mine engineering properties. Many exploration tools and techniques are available to obtain and develop data in the evaluation of existing impoundment structures. Some of the com- monly used exploration tools are described below. • Geologic map and geologic cross sections. 1bese are essential tools for planning a subsurface exploration program, specifically in evaluating foundation conditions of the impoundment under investigation. If geologic maps and geologic sections are available, they should be updated to show existing features such as slope instability, groundwater seeps. the potential for impermeability and piping around and under the major structures and appurtenant wolb. as well as within the reservoir area. • Soil sampling. Information that can be obtained from drilling is required for earth and rock dams if the original site conditions, design criteria and analyses, and construc- tion records are unavailable or if visual inspection or performance records indicate that the facilities may not be performing adequately. The purpose of drilling is to obtain disturbed and undisturbed subsurface soil samples that provide information used to construct a three-dimensional subsurface picture. • Rock sampling. Core drilling with diamond drill equipment is the exploration method most commonly used for concrete or masonry structures and for relatively hard bedrock foundations. The core drilling program provides a means of investigating and evaluating the structure and its foundation, construction joints, and any cracking in the concrete or masonry. • Boring records. Logging all samples obtained in the drilling program and measuring groundwater in the drill holes is most important. Stage 2 3-3 ASCEIEPRI Guides 1989 Laboratory testing Small-scale hydro elements • Trenching or test pitting. These methods of exploration open a wider area of shal- low subsurface materials to detailed examination than does drilling. The excavation can be done by backhoe, bulldozer, or manually. In situ field tests can be conducted, and disturbed or undisturbed samples can be obtained from exploratory trenches or test pits. • Sample testing. Laboratory tests are performed to obtain data for rational evaluation of conditions and for use in engineering analyses. For convenience, laboratory tests are divided into two categories: (l) soils and (2) rock or concrete. All testing should be performed at established laboratories by experienced personnel. Laboratory testing of soils and soft rock consists of classification, physical properties test- ing, and engineering properties testing. Oassification and physical properties tests are based on a recognition of the various types and significant distribution of soil constituents, considering gradation characteristics, and plasticity of materials. Grain-size distribution data and the results of Atterberg limits tests provide the information, except for the deter- mination of organic content, to properly classify the material. Tests that are commonly per- formed to determined engineering properties of soils include compaction tests to determine the moisture-density relationships of materials containing a significant percentage of fines; relative density tests to determine the maximum and minimum densities for relatively clean sands and gravels; consolidation tests; permeability tests; and shear strength tests. Tests on concrete and hard rock samples are normally limited to determining the uncon- fined compressive strength. D. DEVELOPMENT OF SITE LAYOUT 1. General Small-scale hydroelectric developments typically consist of the following elements: • A dam to maintain the upstream water level, divert water to the power plant and in some cases, provide a reservoir for storage water • A spillway to permit floods or excess flows to be passed safely over or around the dam • One or more outlet works to permit controlled discharges to be made to the river, or other conveyance conduits or channels • A powerhouse containing the turbine-generator equipment • Waterways connecting the intakes with the powerhouse or outlet works; these may be steel or concrete conduits, a canal, or simply passages formed in a combined dam and powerhouse structure • Bypass works (i.e., spillways and outlet works) to permit discharges when the turbine is inoperative, (required at certain sites) • A switchyard and transformer through which the generator is connected to the trans- mission line at the stepped-up line voltage • A transmission line connecting the project with the power grid or point of use for the power • Special items such as fish ladders and desiltation works (required at certain sites) ASCE/EPRI Guides 1989 3-4 2. Project Layout The following considerations are necessary when developing a project development plan and determining project layout: • Flow and flood data • Method of operation • Project configuration, dimensions, and governing elevations • Construction plan and requirements for diversion and care of water • Elevations of headwater and tail water (minimum, normal, maximum) • Powerhouse and turbine type and number of units • O&M requirements (powerhouse crane, mobil crane, roof hatches, etc.) • Need for and capacity of intake and penstock • Need for bypass works, means of purging sediment and bedload deposited in front of intake • Method for connecting to existing facilities • Need for remedial or repair work. • Need for special works (fish facilities, etc.) • Transmission line requirements • Needs for project access • Sensitivity to environmental and archaeological issues Where a new small hydropower facility will be installed at an existing dam, the follow- ing general categories of project layout are applicable: • A new intake structure, penstock, and powerhouse will be constructed; an approach channel to the intake and a tailrace connecting the power plant to the river or other channels may be necessary (the intake may be located at a dam or on a canal); • An independent power plant will be attached to the downstream end of an existing conduit in a concrete dam or intake structure. • A penstock and an independent power plant will be attached at the downstream end of an existing outlet work. of an earth dam ( the existing outlet works typically con- sist of a tunnel or concrete conduit with a discharge valve located at midlength or on a steel conduit at the end of the tunnel or corxluit; though sometimes a control gate is provided at the upstream end). • A power plant acts as. or is integral with, the dam. E. ASSOCIATED AND JOINT-USE FACILITIES 1. Associated Facilities Other facilities that are occasionally associated with small-scale hydropower projects include: • Multilevel outlets. Gated or valved ports are occasionally installed in the intake structure to permit the diversion of water from different elevations in the reservoir to allow the mixing of water with variable temperatures and dissolved oxygen char- acteristics for water supply or fishery needs. Necessary considerations Categories of project layout 3-5 ASCE/EPRI Guides 1989 • Fish ladders. Fish ladders often consist of a series of concrete chambers rising in ele- vation in small steps. A steady flow of water is passed through the ladders to allow fish to migrate over or around the dam. • Downstream fish migration. Chutes, pipes, or other facilities are often installed to facilitate the movement of migrating fish downstream past the dam and hydro project. • Mechanical means of moving fish upstream. A scheme is used whereby fish are trapped below the dam, lifted out in a tank, and transported over the dam either by cable or truck. These are occasionally used to move upstream-migrating fish past the dam. • Development of new spawning grounds. A method of mitigating the effects of pro- ject development on upstream-migrating fish is to create new spawning grounds downstream from the dam. 2. Joint-Use Facilities Possible joint uses of small hydro power projects include: • Domestic water supply • Irrigation water supply • Stteamflow improvement • Flood control • Recreation ASCE/EPRI Guides 1989 CHAPTER 4. HYDROLOGIC DATA CONTENTS Section Page A. Introduction ................................................................................................................................................. 4-1 B. Streamflow records ..................................................................................................................................... 4-1 1. Representative record ............................................................................................................................. 4-2 2. Evaluation procedures ............................................................................................................................. 4-2 C. Reservoir characteristics ............................................................................................................................. 4-3 D. Tailwater rating curve ................................................................................................................................. 4-3 E. Spillway adequacy ...................................................................................................................................... 4-4 F. Sedimentation load ...................................................................................................................................... 4-5 G. Water quality studies ................................................................................................................................... 4-5 H. References ................................................................................................................................................... 4-6 ASCE/EPRl Guides 1989 CHAPTER 4. HYDROLOGIC DATA A. INTRODUCTION This chapter identifies the types and sources of hydrologic data required to perform Introduction hydropower studies at sites for small-scale hydro projects. This chapter also includes a brief description of the need for and use of this information. B. STREAMFLOW RECORDS The most important type of hydrologic data required for a hydropower study is a long-term streamflow record of the flow available for power production. The major source of stream- flow data is the U.S. Geological Survey (USGS). Streamflow data, diversion and water-use records are also available from other federal agencies, water users, and state and local agencies. Surface water records collected by the USGS are published by state for each water year in Water Resources Data. In addition to the summary of streamflow data, that publication also contains a detailed description of the station location. summary statistics for the period of record, extreme events during the year, problems in the record, and a listing of nearby diversions that affect the streamflow record. These documents are published annually and are available from the USGS district office of each state. Sources or data The entire historical record of a station is available from the USGS through the W AT-W A TSTORE STORE system, the USGS's National WATer Data STOrage and REtrieval System. Mean daily streamflows are available for the entire historic record for any active or retired gaug- ing station. In addition to the mean daily streamflow, WATSTORE contains additional information useful for hydropower studies: • Listings of all active and retired gauging stations within a state, including all water quantity and quality parameters that have been collected and the beginning and end- ing dates of each record • Peak flows and low flows • Water surface elevations, where collected • Water temperatures, daily maximum, minimum, and mean, where collected • Dissolved oxygen, daily maximum, minimum, and mean, where collected • Suspended sediment, where collected • Ionic concentrations, where collected W A TSTORE contains a number of computer programs and routines that process the data and print useful summaries. These computer programs and routines include: • Flow-duration curves that can be processed for the entire record, part of a record, month of year, groups of months or seasons of a year, and any combination thereof. Computer programs 4-1 ASCE/EPRI Guides 1989 Adjust historical record Evaluation steps • Monthly and annual statistics, including mean, variance, standard deviation, skewness, coefficient of variation, and percentage of average value that can be processed for the entire record or part of record. • Combination of station records whereby two or more stations can be combined by addition or subtraction to create a separate record that can be processed by any W AT- STORE program or process. • High-flow and low-flow event statistics whereby the 1-, 3-, 7-, 14-, 30-, 60-, 90-, 120-, and 183-day, low-and high-flow events may be calculated from the entire record or any portion of the record for various recurrence intervals for annual, monthly, or sea- sonal values. W A TSTORE processing can be obtained from the local USGS office or from any of the service bureaus that have access to the USGS WATSTORE system. 1. Representative Record The streamflow data is used to estimate the average annual energy that can be produced, and the streamflow data should reflect the conditions present when electrical generation occurs. If the historical record represents the future flow conditions, it can be used without modifi- cation. If not, the historical record may need to be adjusted for changes in the hydrologic regime, present and future diversions, inflow, seepage, evaporation, and minimum flow requirements. Standard hydrologic techniques may be used to adjust the historical record. If a streamflow gauge is not located near the hydroelectric site, a streamflow record from a representative nearby gauge may be adjusted by standard hydrologic techniques. Hydrologic characteristics that must be considered include drainage area, topography, soils, and precipitation patterns. If an abandoned gauging station is located near the hydroelectric site, the streamflow records from that station can be analyzed and compared with an equivalent period of record from an existing gauging station, then to the longer record from the existing station to eval- uate the adjustments in records at the abandoned station. Stochastic procedures are not justified for most small hydroelectric sites except in extreme instances where dependable capacity is a significant issue and the impact of an extreme drought should be analyzed during the feasibility stage. 2. Evaluation Procedures The following is a process by which representative data can be obtained from W A TSTORE or other sources for the hydrologic study: 1. Obtain a listing of all current and abandoned gauges near the proposed site to deter- mine the gauges and the period of record that should be used in the study. 2. Obtain monthly and annual statistics for the period of record to determine the seg- ments of the period of record that are applicable and should be analyzed, and to determine the seasonal nature of the streamflow regime. ASCE/EPRI Guides 1989 4-2 3. Obtain mean daily streamflows for specified periods and flow-duration curves for the applicable study period for the annual period, any critical months, and any seasonal combination of months, e.g., high-and low-flow months, seasons of the year, or months with high avoided cost payments. 4. Obtain supplemental data for low-flow events, floods, and other physical or chemical parameters. After obtaining and analyzing the above hydrologic data, other data needs are inevitable to resolve new concerns. C. RESERVOIR CHARACTERISTICS For hydroelectric projects where the storage of a reservoir is used or where the head is not constant, the storage-elevation and the area-elevation characteristics of the reservoir must be known. This data is necessary for the sequential streamflow routing analyses. If the storage-elevation and area-elevation characteristics are not available from the owner or design engineer for the reservoir, then the characteristics must be computed using stan- dard hydrologic techniques. If the only information available is not current or predates the construction of the reservoir, the characteristics should be used cautiously until the validity of the data is confirmed. It is not unusual to have a reservoir's volume substantially reduced by sedimentation. If the project is larger than 5 MW, an application for a FERC license requires an area- capacity curve showing the gross storage capacity and the usable storage capacity of the impoundment with a rule curve showing the operation of the impoundment and how the usable storage capacity is to be used. If the project is under 5 MW, an application for a FERC license only requires the reservoir surface area in acres and, if known, the net and gross storage capacity. If easily available from existing records, pool-elevation duration data is helpful in evaluat- ing the operational characteristics of the reservoir with respect to the maintenance of head. Pool-elevation duration data improves the accuracy of preliminary computations of energy production and serves as a check if reservoir operations are modeled. D. TAILWATER RATING CURVE The tailwater rating curve is necessary to define the discharge capacity of the channel downstream from the project. It is one of the most important hydrologic items needed for the evaluation of small-scale hydroelectric projects at in-stream dams and power plant analyses. In most channels downstream from dams the head, as measured between the headwater on the dam and tail water in the downstream channel, decreases with increasing flow because of the effect of backwater in the downstream channel. If the tail water rating curve is ignored by the assumption of constant head, estimates of power production can be substantially overstated. Computing characteristics Area-capacity curves Pool-elevation duration data Importance of curve 4-3 ASCFJEPRI Guides 1989 Dam safety report Tail water elevation is a function of downstream channel geometry, discharge, and down- stream backwater effect. At some project locations, tailwater rating curves have been established from historic records of tail water elevation and discharge. In some instances, a tailwater rating curve can be determined from observations on a range of flows. When opportunities for direct tail water measurements are nonexistent or difficult, tail water eleva- tions can be estimated by a variety of computer programs for backwater computations, including HEC-2, Water Surface Profiles. For a run-of-river project, the tailwater rating curve and the headwater rating curve can often be used to establish a head-discharge curve. Data from the head-discharge curve can be combined with the flow-duration data to establish an energy generation duration curve. For a peaking project, a steady-state backwater profile condition may not be established. In such cases, unsteady flow conditions predominate, and more detailed hydraulic analyses of unsteady flow conditions are appropriate to define the tailwater conditions. The potential for future channel degradation should also be addressed in the design of new hydroplants. Some sites have experienced as much as a 4-foot drop in the tailwater in 15 years. This could present some serious problems that must be prevented in the design. For example, if the spillway requires natural tailwater development to produce a hydraulic jump and obtain necessary energy dissipation, channel degradation could result in sweep- out at even relatively low flows and serious erosion endangering the stability of structures and abutments. In addition, the setting of most turbines (with the exception of Pelton turbines) requires some minimum submergence to prevent cavitation. If channel degradation occurs and the required submergence cannot be obtained. frequent and expensive maintenance may be required. An artificial sill can be provided in the tailrace to maintain the minimum tailwater required to obtain the desired submergence. E. SPILLWAY ADEQUACY The determination of spillway adequacy is essential to the evaluation of the integrity of an existing dam. If the spillway capacity is inadequate, the potential for overtopping of the structure is increased, and the associated safety issues should be evaluated in detail. A license application to FERC for a project that exceeds 5 MW must include the basis for the spillway design flood in sufficient detail for independent staff evaluation. The spillway design flood is the largest flood that a given project is designed to pass safely. If a dam safety report has been issued, an evaluation of spillway adequacy has been com- pleted and reported. Evaluations and reports on dam safety inspections can be obtained from inventories maintained by the district offices of the Corps of Engineers and from the state agencies responsible for dam safety evaluations. Reports should also be available from the owner of the dam. If no study has been performed or if there is reason to believe that conditions have or will be changed, spillway adequacy should be evaluated. Two primary issues should be ASCE!EPRI Guides 1989 4-4 addressed-the flow capacity of the existing spillway and the design capacity that the spillway should pass. The computation of the flow capacity of the spillway is a hydraulics problem adequately described in several references [USBR, 1977]. The determination of the appropriate discharge for the spillway design flood is based upon the height and capacity of the impoundment and the hazard potential classification. The lat· est criteria for the selection of the spillway design flood are available from the applicable state water resource agency, the Federal Emergency Management Agency, and the district office of the Corps of Engineers. F. SEDIMENTATION LOAD A knowledge of the sedimentation load of the stream is important to the design of facilities and selection of equipment. Not only can sediment deposited behind the dam or diversion structure fill the reservoir, reduce storage, and impair the operation of gates, but sediment passing through the turbine can wear and erode various machine parts. The suspended sediment load should be measured and furnished to the turbine supplier so that the wear and erosion of machine parts can be assessed. The bedload and suspended load should be analyzed to determine the potential for deposition within the reservoir. When the bedload is significant, sluicing of sediment may be required throughout the life of the project to keep the intake area free, and appropriate gates and sluicing facilities should be designed into the structure. Sluicing is effective for only a short distance upstream of the sluice outlet. G. WATERQUALITYSTUDIES Water quality data is needed to assess the potential for changes in water quality conditions from the implementation of the hydroelectric project. The need for water quality data should be determined early in the project. It is related to environmental issues, as described in the environmental chapters of these Guidelines. Exhibit E of a license application to FERC requires the applicant to provide: "A description of the seasonal variation of existing water quality for any stream, lake, or reservoir that would be affected by the proposed project, including (as appropriate) mea- surements of significant ions, chlorophyll a, nutrients, specific conductance, pH, total dissolved solids, total alkalinity, total hardness, dissolved oxygen, bacteria, temperature, suspended sediments, turbidity, and vertical illumination." Water quality data is available from the USGS WATSTORE system, state water resource agencies, state and federal water quality agencies, and state and federal fish and wildlife agencies. Flow capacity Problems Measurement and analysis Need for data Source of data 4-5 ASCE/EPRI Guides 1989 H. REFERENCES COE, Hydropower Manual; Engineering and Design, 1985. This new version of the Corps of Engineers plan- ning manual contains infonnation on available programs and their usage. USBR, Design of Snuzll Dams, 3rd ed., Bureau of Reclamation, Denver, Colorado, 1987. ASCE/EPRI Guides 1989 CHAPTER 5. ESTIMATING PLANT CAPACITY AND ENERGY OUTPUT CONTENTS Section Page A. Data requirements and sources .................................................................................................................... S-1 I. Physical and operational data ................................................................................................................. 5-1 2. Hydrologic data ....................................................................................................................................... 5-1 3. Data sources ............................................................................................................................................ 5-2 B. Technical characteristics of generating units ....................... , ...................................................................... 5-2 C.'fypical overall plant efficiency ....................................................... , ........................................................... 5-3 D. Flow-duration method ............................................................................................................................... ,5-3 1. Energy-flow-head relationship ...................................................... , ....................................................... 5-3 2. Flow-duration curve ............................................................................................ , .................................. 5-3 E. Determining installed capacity and energy output using the flow-duration method ................................. .5-4 F. Dependable capacity ................................................................................................................................... 5-7 G. Storage operation and sequential analysis ................................................................................................... 5-8 FIGURES Figure 5-1 Application ranges for hydraulic turbines .............................................................................................. S-2 5-2 Example flow-duration method, one unit. ............................................................................................. 5--4 5-3 Example flow-duration method, two units , ........................................................................................... 5-6 ASCE/EPRI Guides 1989 CHAPTER 5. ESTIMATING PLANT CAPACITY AND ENERGY OUTPUT A. DATA REQUIREMENTS AND SOURCES The hydropower capacity and potential energy output of a prospective development site, whether it is new or an addition to existing facilities, depends primarily on the magnitude and distribution of the flow and the head available at the site. Some idea of the flow avail- ability during low-flow seasons and during historical low-flow years is also needed to esti- mate the likelihood of credit for dependable capacity. However, power benefits are typical- ly based on average annual energy generation because capacity usually does not meet the standard definition of "dependable." More specifically, data requirements can generally be categorized into two groups: (1) physical and operational data, and (2) hydrologic data. 1. Physical and Operational Data Physical and operational data required to analyze either an existing retrofit or a new hydro facility are fundamental to estimating plant capacity and energy output. The following items are required to perform this analysis: • Maximum height of dam • Spillway crest elevation and configuration • Maximum permitted lake water surface elevation • Normal water surface elevation • Maximum drawdown for operation • Outlet configurations, locations, and ratings • Seepage losses • Reservoir surface area versus storage (rating) 2. Hydrologic Data Basic information and data are needed about the drainage area and runoff characteristics of the watershed and about any major water usage or diversions upstream of the dam. If daily flow data are readily available (at least 20 years is desirable), flow-duration data can be constructed from which average annual energy estimates can be computed. The accuracy of the capacity and energy estimates depends on the combined accuracy of flow character- istics and corresponding head variability. The following hydrologic items are necessary to complete the capacity and energy calculations: • Drainage area • Daily flow data (minimum 20 years if possible) • Flow-{Juration relationship • Flood hydrographs • Evaporation rates • Minimum flow release requirements • Tailwater rating Data requirements and sources Physical and operational data Hydrologic data 5-1 ASCEIEPRI Guides 1989 Data sources Thrbine/ generator 3. Data Sources The most logical source for both the physical and hydrologic data is the operator-<>wner of the existing facility. The U.S. Army Corps of Engineers has Phase I Safety Inspection Reports on most existing dams that are candidates for small hydro retrofits. These reports provide substantial physical and hydrologic data. In addition. the files of agencies charged with permitting and inspecting dams are a primary data source in many states. Most of the continuous flow data are published by the U.S. Geological Survey (USGS). Mean daily flow data are published by state and 5-year summary reports are published by major river basin grouping. Data published by the states and by the USGS are usually available in the state libraries, university libraries, or libraries of federal agencies such as the Corps of Engineers, Bureau of Reclamation, and Soil Conservation Service. B. TECHNICAL CHARACTERISTICS OF GENERATING UNITS A major cost of a small-scale hydropower development is the turbine-generator unit Several types of units are available, each designed to operate over a range of heads and capacities. Turbine efficiency is strongly conditioned by specific speed and size. If efficiency is important at the specific site studied, consult the Conventional Guidelines. Figure 5-1 shows some typical application ranges for various types of hydraulic turbines. This figure is valuable only for screening. Even at the planning stages. technical informa- tion on turbines recently developed specifically for small hydro applications should be used. 3000 2000 1000 500 400 200 E 100 .: 80 'C 60 :ll 40 J: 20 10 a 6 4 2 -/ mE .6rnl I A lr pumr ,--I"• L-··ri 1"-..... . 1-"" . • tn;pulsetl.lrilll* ,.-,... . 1 -.A i ....... .:< . ! ~MUlti• H n 1Jif'IC ....... -··"' ~o-· 'i suge-""" ..... ~ H11 ~[j.!~ ~ .. f'rlncis turbi ... <II'!!_ I . Industrial v L" pump / ~ I Pro~M~I• 1nc:1 I ~ ... ~~ I ~~ K.JI)Ian t\lltliniS i-' ~ I~ ~ :!:r"=~·-· n ~ Single-stage , ..... .. ~ ...-pumps! ·""' ..·:J ..... !1 ·:· lal Bulbuniu . t--... .... \L_ t--_;...--, , ....... I I I .. t--I I) •1 .... r··· r 1 I f< Stindard ized A C ' ~be~rbin~ 1 5 10 20 40 100 400 1000 10,000 100,000 400,000 60 40,000 Turbine output in kW Figure S-1.-Application ranges for hydraulic turbines. Courtesy Alli~halmers. ASCE!EPRI Guides 1989 5-2 -C. TYPICAL OVERALL PLANT EFFICIENCY The following efficiencies can be used as guides for planning purposes. Item Typical average efficiency Range Turbines 86.0 83--90 Generators 96.0 95-97 Speed Increasers 97.0 96--98 Step-up transfonners 98.0 98-99 Transmission lines 98.0 ~97 Step-down transfonners 98.0 98-99 Overall plant water-to-wire efficiency 75.0 70-85 D. FLOW-DURATION METHOD 1. Energy-Flow-Head Relationship The fundamental procedure for generating electrical energy from water stored at different elevations is to convert potential energy to electrical energy by means of a prime mover (turbine) connected to a generator that is, in tum, connected to an electrical power system. This relationship is described by equation (5-1): where: P = power (k.W), QHT] P=IIT Q = flow available for generation (ft3/s), H = head available statistically (ft), 11 = hydroplant average water-to-wire efficiency (in decimal fraction), and 11.8 = conversion constant 2. Flow-Duration Curve (5-1) A flow-duration curve is a cumulative-frequency curve that shows the percent of time that specified discharge values are met or exceeded during a given period. Daily flows should be used in constructing the curve. The relative percentage of time during which each flow in the series has been equaled or exceeded is computed. 1ben the curve is plotted showing the flow on the Y axis (ordinate) and the percent of time on the X axis (abscissa). See example curve on figure 5-2. The area under the flow-duration curve represents the quantity of water available at the site. As a starting point, oonnally flows in the 25-percent exceedance range are selected for analysis of the project installed capacity and energy output When the head is known, the power and energy potential for the site may be detennined using the power equation (5-1). Efficiencies Flow-head relationship Flow-duration curve 5-3 ASCE/EPRI Guides 1989 '(ij' -~ ~ g 1.. Flow-duration method 19000 18000 17000 16000 15000 14000 13000 12000 11000 10000 9000 8000 ······ ·· · ···· · ·· ·· · · · · ······· ·· · ·· · · w;,~e(6~g-~t J't~~ne ····· ········· · ··· · · · · · · ····· ...... ····· ........ . · · · · · · · · · · · ·· · · · · · · · · · · · · · · · · · · · · · 500 cfa Minimum · · · · · · · · · · · · · ·· · · ·· · · · · · · · · · · · · · · · ·· · · · ·· · · · · · · · · 7000 . . . . . . . . . . . . . . . . . . . . . . . ........... Flow Release) 5000 5000 4000 3000 2000 1000 0~--~----,---~----,-- 0 10 20 30 40 50 60 70 80 % EXCEEDENCE Figure 5-2. -Example now-duration method, one unit. E. DETERMINING INSTALLED CAPACITY AND ENERGY OUTPUT USING THE FLOW-DURATION METHOD To demonstrate the flow-duration method, an example is provided showing its use at a small hydro site: 1. Given: • Gross head = 20 feet • How-duration relationship (fig. 5-2) • Minimwn release for fishery= 500 ft3fs • Run-of-river project site 2. Installed Capacity (One Unit): • Plot 500 ft3fs minimwn flow release line on flow-duration curve (area A defined by the 500-ft3fs line on fig. 5-2) • Assume single turbine-generator unit installation • Assume adjustable propeller turbine installation ASCE/EPRI Guides 1989 5-4 • Assume adjustable propeller turbine installation (with flow range of 25% to 115% of design flow) • After a number of iterations, an optimum design flow of 5,200 ft3/s is selected • Turbine design flow= 5,200 ft3/s = Qd • Net design head= 19.3 feet= Hd (selected from head-flow relationship) • Assume turbine-generator efficiency = 86% • Installed capacity: Qdi!J11 _ (5,200)(19.3)(0.86) _ 7 315 kW kW = 11 . 8 -11 . 8 - ' 3. Energy Output (One Unit): • Plot the line representing minimum turbine flow plus minimum flow release on flow-duration curve= 1,300 + 500 = 1,800 ft3/s • Plot the line representing maximum turbine flow plus minimum flow release on flow-duration curve= 6,000 + 500 = 6,500 ft3/s • Calculate area B on flow-duration curve (fig. 5-2), which represents the average flow as if it were available to the turbine 100% of the time= 3,220 ft3/s = Q100 • Energy output: Adjustment of efficiency when using annual flow-duration curve = 0.95 = 171 Adjustment of efficiency due to tail water (head) fluctuations = 0.97 = 112 Adjustment to consider 4% unscheduled down time = 0.96 = 173 Water-to-wire efficiency= 0.75 11n (See section B) Turbine flow available 100% of the time= Q 100 = 3,220 ft3/s net head= 18.7 feet= Hn • Output = = = • Plant Factor: QlOOHn 11n111112113(8, 760) 11.8 (3, 220 )( 18. 7)( 0. 75)( 0. 95)( 0. 97)( 0. 96)(8, 760) 11.8 29,660,000 kWh/yr 29,660 '(XX) kWh/yr PF= (7,315kW)(8,760h/yr) =0 ·46 4. Alternative (Two Units): • Minimum release= 500 ft3/s (area A under curve on fig. 5-3) • Assume adjustable blade propeller turbines (flow range 25% to 115% of design flow) • After a number of iterations, design flows are selected for the two turbines as follows: Qd turbine 1 = 2,000 ft3/s (flow range = 500 to 2,300 ft 3fs) Qd turbine 2 = 9,200 ft3/s (flow range= 2,300 to 10,600 ft3/s) Energy output Alternative 5-5 ASCEIEPRI Guides 1989 19000 18000 17000 16000 Waxlmum Plant Flow 15000 Plus Wlnlmum Release ·············································· ··········· · · 14000 (12900 + 500 = 13400 cfs) ~ ................................................................................................................................................................. .. 13000 12000 ";;-11000 -~ 3: ~ 10000 9000 8000 7000 6000 5000 4000 3000 2000 1000 Wlnlmum Plant Flow Plus Wlnlmum Release ····· (500 + 500 = 1000 cfs) ...................................................................................................................................................................................... ··············8······················· .................................................................... . No Generatlor . ... . . . .. . . . .. . . ... ... . .. .. . .. ........... ·I ~-------------------04---~----~--~--~~ 0 10 20 30 40 50 60 70 80 90 100 110 % EXCEEDENCE Figure S-3. -Example flow-duration method, two units. Minimum plant flow= 500 ft3/s Maximum plant flow = 2,300 ft3/s + 10,600 ft3/s = 12,900 ft3/s • Design heads: H 1 = 19.5 feet H2 = 18.7 feet • Thrbine generator efficiency = 86% = 1]1 • Installed capacity: Q d 2H 21] I ( 9' 200 ft 3 I s ) ( 18. 7 ft)( 0. 86) kW T 2 = ll . 8 = 1l . 8 = 12,5 40 kW • Total plant installed capacity= 2,840 + 12,540 = 15,380 kW • Minimum plant flow plus minimum release flow = 500 ft3/s + 500 ft3/s = 1,000 ft3/s (broken line on fig. 5-3) • Maximum plant flow plus minimum release flow = 12,900 ft3/s + 500 ft3/s = 13,400 ft3/s (upper line on fig. 5-3) ASCE/EPRI Guides 1989 5-6 • Flow available to turbines 100% of the time (area Bon fig . .>-3) = 4,600 ft3fs • Net plant head with both units operable= Hp = 17.8 feet • Energy output: Q 100 = 4,600 ft 3/s Hp = 17.8 feet 11n = 0.75 771 = 0.95 112 = 0.97 773 = 0.98 (for two-unit plant, unscheduled down time is reduced to 2%) Output = Ql00Hp7J n1117]27]3(8, 760) 11 .8 = 40,330,000 kWh/yr • Plant Factor: PF = 40, 330,(XX) kWh/yr (15, 380 kW)(8, 7&J hr) = 0 ·30 F. DEPENDABLE CAPACITY The traditional definition of dependable capacity applied to a small hydro facility is the capacity that under the most adverse flow conditions of record can be relied upon to carry its share of the system load, provide dependable reserve capacity, and meet firm power obligations. If the small hydro plant is in an isolated system, its dependable capacity is lim- ited by the minimum flow occurring at any time. In unregulated remote streams, the avail- able flow is frequently zero. As a part of a larger system, the dependable capacity is affected by the characteristics of the other plants in the system and how the low-flow period relates to the occurrence of peak loads on the system. For example, low summer stream flows may be of small signifi- cance in a system with a winter peak load. In addition, the existence of excess capacity and storage reservoirs at other hydroelectric projects in a system during low-flow periods may influence the extent to which dependable capacity can be allocated to a run-of-river pro- ject. The criteria for determining whether or not dependable capacity exists should there- fore be made with regard to the system in which the plant will operate. The energy that can be generated by the plant during the period it can be considered dependable is referred to as finn energy. Computing this energy requires determining the lowest period of flow that has occurred historically at the time of year the peaking capacity in the power system is critical. The critical period may range from a day for an isolated run-of-river plant where the system is composed only of thermal plants to several months where a storage reservoir can be used. The minimum flow obtained from daily streamflow records occurring at the appropriate (usually minimum) head (obtained from daily streamflow records) provides the lowest and, therefore, the dependable capacity (provided it is larger than the minimum turbine flow). However, this capacity may have to be sustained for only a few hours per day, during the system's peak loads. Hence, if reservoir storage exists, it may be possible to conserve the flows during some hours to give an increased supply during the period of the system peak. Usually, some minimum flow is required in the river at all times to satisfy fishery or other Dependable capacity Firm energy 5-7 ASCE/EPRI Guides 1989 Sequential analysis Continuity equation needs. This approach is considered conservative because the minimum flow does not nec- essarily occur at the same time of the year as the maximum peak requirements of the sys- tem. As an alternative, many utilities often accept the flow that is equaled or exceeded 90 to 95 percent of the time as the critical minimum flow used to compute dependable capacity and firm energy. Although this method is not considered the most conservative approach, it may still underestimate the capacity that can be used during periods other than critical. There is no completely satisfactory method of determining the dependable capacity in a simple manner without considering the system. However, the advantages of small hydro projects are that they rarely influence the overall system with which they are interconnect- ed and they have a high availability rating with low outage time. G. STORAGE OPERATION AND SEQUENTIAL ANALYSIS At storage projects with variable head, it is not possible to estimate energy output using the flow-duration method without error because the volume of flow that passed the project at a particular head is unknown. Moreover, if the reservoir fluctuation falls outside the turbine head limits, then the volume of flow unavailable to the turbine during these periods is unknown. Therefore, a sequential operation analysis is used in these cases to obtain more accurate energy output conclusions. Sequential streamflow routing methods can be applied to almost any type of hydropower analysis, including studies of the following types of projects: • Run-of-river projects where flow and head vary independently • Run-of-river projects with pondage • Projects with flood control storage only • Projects with conservation storage not regulated for power • Projects with storage regulated only for power • Projects with storage regulated only for multiple purposes including power • Peaking hydro projects • Pumped storage hydro projects The sequential streamflow routing procedure was developed primarily for evaluating stor- age projects and systems of storage projects and is based on the continuity equation: dS=l-0-L (5-2) where: dS = change in reservoir storage, I = reservoir inflow, 0 = reservoir outflow, and L = losses (evaporation, diversion, etc.). ASCE/EPRI Guides 1989 5-8 Equation (5-2) is applied sequentially for each time interval in the period studied to obtain a continuous record of project operation. The chosen time interval should be consistent with the accuracy desired. In the case of power estimates during feasibility studies, the maximum time interval used should not exceed one month. Feasibility estimates of firm energy should be based on daily or weekly time intervals during critical periods using all available information on project purposes, diversions, seasonal storage levels, losses, tail- water rating, and plant efficiency data. If dependable capacity is not a consideration, a monthly analysis for the entire period of record is usually sufficient Energy output can then be estimated by applying the reservoir outflow values to the water power equation. At storage projects, the head and efficiency as well as the flow may be affected by the operation of the continuity equation, through the dS component. Normally, the range of efficiency characteristics of the turbine-generator equipment for various flows and heads would be incorporated into the analysis rather than a uniform efficiency for all head values. Sequential streamflow routing can require considerable data manipulation and thus can best be accomplished by a computer model. Several sophisticated models are capable of handling such functions as automatic optimization of firm energy production, evaluation of multiple-project systems, and operation of projects or systems to meet the requirements of flood control. Estimating energy output Computer model 5-9 ASCE/EPRI Guides 1989 Section CHAPTER 6. POWER SYSTEM USE AND CONNECTION REQUIREMENTS CONTENTS Page A. Introduction ................................................................................................................................................. 6-1 B. Need for }X)wer ............................................................................................................................................ 6-1 C. Power marketing ......................................................................................................................................... 6-2 1. Powercontracts ....................................................................................................................................... 6-2 2. PURPA .................................................................................................................................................... 6-3 D. Power system connection requirements ...................................................................................................... 6-4 ASCE/EPRI Guides 1989 CHAPTER 6. POWER SYSTEM USE AND CONNECTION REQUIREMENTS A. INTRODUCTION Along with the plant capacity and the energy output, discussed in chapter 5, attention should also be given to the use of power. Hydropower can be used in a power system in several ways, including: • Peaking loads • Intermediate loads • Base loads • Combinations of peaking, intermediate, and base loads Hydroelectric plants have the ability to come online rapidly and to respond quickly to load changes. Because of this quick reaction, hydroelectric facilities have been traditionally viewed as a peaking resource. However, most potential small-scale hydro developments are constrained from peaking operation by operating limits because of a run-of-river con- figuration or because operating conditions are imposed to protect the environment or to enhance recreational opportunities. Other small hydro projects are constrained from the daily and weekly shaping of power discharges to fit power demand by lack of storage or pondage. However, some load-following is possible within these constraints, by providing partial base load using minimum flow releases and by using a small amount of storage for peaking. In any event, increasing storage is not an alternative generally available at small- scale hydropower projects. If existing project purposes require release patterns that are near enough to the energy demand or usable on the load, some dependable capacity can be cred- ited to the project. The use of small-scale hydro to most utility systems is not of major importance where stor- age or pondage is not available. Where streamflow is dependable, the small-scale hydro plant may replace an increment of thermal capacity. Where streamflow is not dependable, the hydro energy may be usable only for displacement of the energy output of existing thermal plants. However, in some cases, the value of energy displaced may be high. In California and New England, where a substantial portion of the generation is oil-fired steam, the benefits attributable to this type of operation may be substantial. In summary, hydro energy has a fuel cost of approximately zero and will normally provide the best value in minimizing system operating costs when it is delivered during peak load periods. B. NEED FOR POWER Traditionally, the need for power is evaluated by performing a load-resource analysis so that the supply (power resources) and demand (power loads) can be evaluated. Small-scale hydropower does not often solve such major problems and, therefore, a power marketing analysis is more suitable. The power marketing analysis is performed to ensure that there is a market or use for the power generated. Hydropower uses Operating limits Load- following Load-resource analysis Power mar- keting analysis 6-1 ASCE/EPRI Guides 1989 Uses of power Purpose Wheeling power Power produced by small-scale hydroelectric facilities is normally used in one of the fol- lowing ways: • Use of power at site of generation. When power is used at or adjacent to the power plant location, the value of the power is the avoided cost of purchased power. • Wheeling of power to site away from power plant. When power is wheeled, it is placed into the power lines of the utility and transponed to a distant site, and the transporting utility charges a wheeling fee for the use of its facilities. The value of the power is the cost of avoided purchases at the site of use, less the wheeling fee. • Sale of power to utility at PURPA rates. When power is sold to a utility, the utility is required by PURP A (Public Utility Regulatory Policies Act) to pay a rate equal to the avoided cost of new facilities. Sometimes long-term contracts can be negotiated at rates less than PURP A rates and on terms favorable to both panies. • Sale of power to third party. Although the sale of power to someone other than the utility is an attractive alternative, it can make the seller a utility and subject to regula- tion by the state utility commission. An analysis of state utility regulatory require- ments should be obtained before pursuing this alternative. C. POWER MARKETING Power marketing is critical to the successful planning of a small-scale hydro project. Tile purpose of power marketing is to select a market, usually an electric utility, to achieve the best economic rerum. Sometimes a choice of electric utilities is available, but the choice may be influenced by regulatory requirements. Electrical utilities pay different rates for hydroelectric power. Rate differences may depend on the power source mix, recent capital improvements, and operational costs. Therefore, the economics of a project may be improved by selecting a utility that pays a higher rate. Usually, the service area of electrical utilities is regulated by the state, and the utility may not connect to a generating source outside its certified area without approval by the regulat- ing agency, sometimes after a public hearing. Therefore, in addition to inquiries with the local electrical utility, inquiries should be made with the state regulatory agency. In those rare but fonunate cases when different electrical utilities serve on opposite sides of the stream, the higher rate may be obtained by locating the powerhouse on the appropriate side of the stream. In addition to selling power to an investor-owned utility, power may be sold to a municipal utility or a rural electric cooperative. The wheeling of power may be allowed under rare circumstances. When power is sold to a nonlocal utility, the local electrical utility may transpon, or wheel, the power to the pur- chasing utility. In such cases, the wheeling utility receives payment for wheeling the power. To wheel the power to another utility, either the wheeling utility must agree to transpon the power or the state regulator must require utilities to wheel the power. The cost of obtaining wheeling agreements may preclude acquiring such an agreement 1. Power Contracts The developer of a small hydro project who intends to sell the energy produced to the utili- ty distributing the power must negotiate a power sales contract. To finance a small hydro ASCE/EPRI Guides 1989 6-2 project without other securities as collateral, lending institutions generally require the Power sales developer to negotiate a power sales contract that extends beyond the number of years in contract which there are debt service payments. In general, the two types of power contacts now written are: 1. Those with levelized energy rates for a specified time (which recover all facility costs Types and include some profit for the developer) 2. Those with energy rates that float with inflation and the cost to the utility of either purchasing energy elsewhere or building sufficient plant capacity to replace a like amount of energy (which results in some uncertainty regarding the potential profits for the developer) In general, type 1 is less risky in terms of the developer's ability to project a revenue stream based on the average annual energy output from the project. However, undepend- able plant energy output caused by design, construction, or equipment flaws, or extremely low-flow periods still pose significant risk for the potential developer. Type 2 provides the developer with less certainty concerning an annual revenue stream from the project over the debt service portion of the project life, but is more likely to result in higher unit prices paid for the energy in later years. A typical contract will normally specify: • Equipment required to be purchased and installed by the developer to protect the utility electrical system • Insurance covering liabilities arising from the operation and interconnection of the small hydro facility with the utility system • Phase, current, frequency, voltage, and delivery location of the energy generated by the project • Sale price • Termination procedures • Reasonable inspection provisions • Interruption provisions Potential developers should depend on individuals experienced and knowledgeable in power sales contract and rate negotiations to conduct discussions with utilities identified as potential purchasers of the project energy output. Tile advantage to the developer when using this approach is the ability to face the utility with a negotiating team knowledgeable about regional power capacity and energy needs, prevailing energy market rates, and stan- dard utility contact provisions. State public utility commissions (PUCs} normally have information about the state options available for power sales contracts. 2. PURPA PURPA specifies that purchasing utilities must purchase the output from qualifying small hydro facilities. Small hydro projects developed by independent power producers (includ- Typical contract specifications Experience of individuals 6-3 ASCE/EPRI Guides 1989 Voltage at point of inter· connection Type generator ing industrial concerns, electric cooperatives, and municipalities) that qualify under PURP A are those where: • The installed capacity of the project is no more than 80 MW, and • Utility equity investors do not hold more than a 50-percent share in the project. PURP A requires that the purchasing utility offer to purchase the total output of energy or capacity or any portion of either that the qualifying facility wishes to offer at the avoided- cost rate payable to a qualifying facility. The avoided.cost rate shall be just and reason- able and in the public interest, and it shall not discriminate against the qualifying power producer. The ultimate responsibility for defining the avoided cost has been assigned to each state's PUC or its equivalent. The developer should contact both the purchasing utility and the state PUC when making avoided-cost power sale contract arrangements under PURPA. Individuals experienced in negotiating power purchase contracts are recommended as an important member of the developer project team. D. POWER SYSTEM CONNECTION REQUIREMENTS Most small hydro projects in the United States are part of an interconnected system of elec- tric loads and generating facilities. Because most small hydro projects do not provide a sig- nificant portion of the required system capacity, the major concern of the local utility is safety and reliability. It is important that an electrical engineer be involved in discussions with representatives of the governing utility during the project planning phase to detennine the electrical interconnection equipment needs and to detennine those items that should be provided by the developer. In some cases, the interconnection equipment is designed, pur- chased, and installed by the utility, but paid for by the developer. Accurate cost estimates at the feasibility study level are important for project fmancing. The major electrical issue is the voltage at the point of interconnection. Occasionally, the issue is as simple as knowing the voltage of the nearest line. At other times, the utility may indicate that the nearest line is inappropriate for interconnection because of system stability issues. If nearby lines cannot be used, longer line lengths or system upgrading may be required to get to a substation or a higher voltage line. In addition, the transfonner, break- ers, and switches will be more costly when connecting to a higher voltage. Another important electrical issue is the type of generator that will be allowed. Some elec- trical utilities prefer synchronous generators instead of induction generators. The type of generator directly affects not only the project costs, but also the electrical protection equip. ment required by the utility. The electrical protection equipment required by the utility includes breakers and switches and can significantly affect project costs. Negotiations on protective equipment should be perfonned in conjunction with a qualified electrical engineer. ASCE/EPRI Guides 1989 6-4 CHAPTER 7. OPERATION AND MAINTENANCE CONTENTS Section Page A. Introduction ................................................................................................................................................. 7-1 B. 1Jesign phase ............................................................................................................................................... 7-l C. Operation phase ........................................................................................................................................... 7-3 D. Operator's manua1 ....................................................................................................................................... 7-3 E. 1Jescription of project. ................................................................................................................................. 7-3 F. Starting the plant ......................................................................................................................................... 7-4 G. Running the plant ........................................................................................................................................ 7-4 H. Stopping the plant ....................................................................................................................................... 7-4 I. Routine maintenance ................................................................................................................................... 7-5 J. Emergency or "need for assistance" procedures ......................................................................................... 7-6 K. Revisions ..................................................................................................................................................... 7-6 L. Maintenance manual ................................................................................................................................... 7-6 M References ................................................................................................................................................... 7-7 ASCE/EPRl Guides 1989 CHAPTER 7. OPERATION AND MAINTENANCE A. INTRODUCTION A full-time operation and maintenance (O&M) staff is not usually appropriate for small hydro projects. Plant operators may be: • Full-time but associated with an adjoining facility such as a water or sewage treatment facility, or other small hydro installation, • Part-time operators who visit the project periodically, • Project owners who live near the project, or • Part-time operators who visit the project periodically and respond to project alarms through a telemetry system. Practical project maintenance must generally be accomplished through local, already- established machine shops, electricians, or contractors. Suppon of the local maintenance team from equipment suppliers is needed. Cost-effective suppon for training work- arounds, repair, and maintenance. The project planning and feasibility document should consider the O&M philosophy to properly evaluate the workability of various project alternatives. Design requirements for the equipment should reflect the O&M philosophy and consider such items as lubrication schedules and level of personnel experience. Necessary suppon facilities (such as medical and sanitary) must be consistent with on-site personnel time. To eliminate costly changes during the design phase, the O&M philosophy must be established during the planning phase and the design must be allowed to accommodate the established philosophy. A document entitled "O&M Philosophy," which is developed during the planning phase, will assist in the preparation of the "O&M/Goals and Objectives" in the design phase. B. DESIGN PHASE As considered and proposed in the planning phase of the project, the O&M concepts and staffing should be determined early in the preliminary design of the project The O&M concepts must be discussed with the project owner and established before formalizing the detail design. The equipment and components selected for use at the project should require a minimum of regular servicing. However, plant operators and maintenance personnel should be famil- iar with the regular servicing required to operate the plant reliably. Preventive maintenance is the primary objective of the maintenance program; i.e., antici- pating potential problems and preventing them from occurring before they have a signifi- cant economic effect on the plant operating costs, loss of revenue, or major repair costs. This will, at times, require shutting down the plant at planned time intervals to make an inspection and perform tests. The plant owner should be involved in the decision concern- ing scheduling of planned shutdowns for maintenance. The plant operator and the mainte- nance personnel are responsible for keeping the owner well informed of potential prob- Types of operators DiscussO&M concept with owner Preventive maintenance 7-1 ASCE/EPRI Guides 1989 Telemetry system lems, indications of wear, and changes in operating characteristics that might require fur- ther investigations. An accurate and detailed record of O&M duties performed of observations made are neces- sary for the safe and reliable operation of the plant. The plant operation log book and log sheets provide a means of recording plant conditions and changes that affect these condi- tions, for future reference. The telemetry system records some of the plant conditions; however, the records kept by the operator and maintenance personnel are also necessary. From these records, potential problems can often be anticipated and prevented. Shutdowns can be scheduled by observing trends in the operation of the plant. This will also help determine which spare parts and consumable materials should be kept on hand at the plant. The O&M staffing and concepts must be considered in the design and specifications of all features. Particular emphasis should be placed on the following goals, objectives, and issues: • Trashrack and screen systems cleaning • Specifications for equipment selection • Security • Spare parts • Alarm, telemetry, and Supervisory Control and Data Acquisition (SCADA) systems • Shutdown devices • Project-and facility-monitoring devices • Bearing selection • Spare parts provided • Redundancy of features • Reliability • Ease of safely implementing control systems • Bypasses • Dedicated maintenance equipment verses shared and rented • Access to project facilities • Availability of supervision and special maintenance needs • Safety and fire protection systems • Project revenues and O&M costs • Auxiliary equipment provided for maintenance • Cold plant start-up time and costs • Maximum operator response time and consequences of late response • Restart time and effort due to de systems, drying equipment, etc. • Agency reporting requirements The operator staffmg considerations should include reliability, response time, skill levels, physical conditions, and adverse weather conditions. A document entitled "Operating and Maintenance/Goals and Objectives" should be devel- oped during the design of the project. The draft will significantly assist the design team, project owner, and constructor in understanding the operational concepts of the project. ASCE/EPRI Guides 1989 7-2 C. OPERATION PHASE The operation and maintenance manual is often separated into two manuals; namely, the operator's manual and the maintenance manual. The operator's manual should be directed towards the qualifications of available operators. The maintenance manual must include details required to replace, repair, disassemble, assemble, adjust, and troubleshoot the plant. A small hydro project may have all the features of a conventional hydro project O&M costs for a small hydro project are not directly related to size or production. Costs are relat- ed more to location, type of project, operation philosophy, utility requirements, environ- mental requirements, and water source. In addition, a good rule of thumb is that operations costs will be significantly (2 to 3 times) higher during the first year. The best way to esti- mate costs is from another small hydro operation with similar projects. Supervisory Control And Data Acquisition (SCADA) systems often help small hydro pro- jects minimize the number of maintenance personnel and improve production time. SCADA systems may vary from a simple automatic dialer that calls an operator for a com- bined alarm condition or plant shutdown, to a multipoint video graphic system communi- cating with a remote monitor or controller concerning all plant status and alarm conditions. The operators of a small hydroplant may be the owner, a person living nearby, or full-time operators. However, a small hydro project usually does not have a fully trained staff of machinists, electricians, millwrights, and engineers to fully operate, maintain, and repair the project. The owner or operator must rely on nearby machine shops, electricians, con- tractors, and the design engineer for support in maintaining and repairing the plant. D. OPERATOR'S MANUAL The operator's manual must include operations procedures in a concise but complete for- mat. It is needed by the operator to operate the plant upon completion of an operator train- ing program. The manual should use a checklist approach with referenced support docu- ments for detail. E. DESCRIPTION OF PROJECT The description of the project should, in a few pages, tell the operator how the planners and designers conceived the project to operate and define the actions necessary under both nor- mal and emergency operating conditions. It should provide a complete and concise functional description of every element of the project, such as: • Intakes. Fishscreens, trashracks, level control, downstream releases, flood conditions, bedload or gravel buildup, automatic penstock shutoff devices, protection devices. • Penstocks. Filling and draining requirements, air and vacuum valves, any isolation valves, drains. • Power canals. Cleaning, capacity, overflows, drains, control structures. • Powerhouses. Ventilation, turbine isolation and bypass valves, intake, tailrace, tailwa- ter minimum and maximum level, any control gates, house electrical systems, etc. Manuals Costs SCAD A O&M support Manual Project elements 7-3 ASCE/EPRI Guides 1989 Project elements Starting Running Stopping • Thrbines. Gates, runner, nozzles, deflectors, lubrication, bearings, type, rpm, alarms, protective devices. • Generators. Lubrication, cooling, type, connection to turbine, voltage, rpm, internal heaters, alarm protective devices. • Switch gear and controls. Protective relays, control system, water level controls, manual and automatic systems, synchronizing, excitation, safety devices. • Switchyard. Transformers, isolation switches, safety devices, alarms. • Transmission lines. Length, voltage, point of connection to service or utility. • Utilities. Representative to contact, requirements for operation, authorization for generating. • Ancillary agreements. Fish and wildlife agency agreements, irrigation, water rights. • Actions. To take during flooding and high water, equipment problems or malfunctions. F. STARTING THE PLANT • Initial conditions. The plant can be started either automatically or manually only after certain initial conditions are met for water level intake, penstock, protective relays (clear), valves, lubrication system, power line, generator condition, and tail wa- ter or headwater conditions. • Dry spin or rotating but not connected to system. List of items to check before generating, initial conditions check, how to stop if generating conditions are not met. • Synchronizing generators. Procedure for manual synchronizing or automatically synchronizing, connecting to grid, generating into a utility or system, rate of loading. G. RUNNING THE PLANT • Run conditions • Controlling generator output • Controlling reactive power output • Water level requirements and control • Reports and logs • Fish release • Intake operation H. STOPPING THE PLANT • Normal stop. Pennits the generator to unload to zero before the generator contractor is opened. 1be normal stop conditions vary depending on the design and equipment used in the project but generally are: • Hot oil temperatures • Hot bearing temperatures • High or low oil levels • Interruption of cooling water • Low batteries • Low or insufficient water levels • Penstock rupture • Governor failure ASCEIEPRI Guides 1989 7-4 • Emergency stop. Opens the generator breaker. The system runs in an overspeed con- dition until the water is prevented from reaching the runner and the system is brought to a stop. An emergency stop is automatic for protection of the systems, usually caused by electrical protective devices. • Restart. Procedures for restarting are different from those for starting the plant If automatic start is provided, list conditions for which the plant will automatically restart and the conditions for which the plant must be manually restarted. • Operational records and logs. Accurate operator records are important for future O&M of the project A preformatted log indicating information to be recorded helps ensure consistent reporting of information. The log varies with the project, equip- ment, environmental requirements, and project features. Typical useful information to be kept in a daily log are: • Water flow and level conditions • Plant production in kilowatts • Weather conditions and temperatures • Bearing and winding temperatures • Alarm conditions • Starting and stopping of the plant • Reasons for plant shutdowns • Trash accumulation and removal • Routine maintenance performed • Plant conditions • Voltage, power factor, vars • Pressures, oil, penstock, cooling systems • Battery conditions • Oil or water leaks • Powerhouse temperatures • Unusual noises, leaks, odors, vibrations I. ROUTINE MAINTENANCE Procedures and requirements for daily, weekly, or monthly maintenance are initially deter- mined by the project design engineers and equipment suppliers. These maintenance items are performed by the operators. In addition, typical routine maintenance should include: • Cleaning the power plant of dust, dirt, insects, trash, oil spills, etc. • Removal of weeds, grasses, trash, etc., outside the building • Safety procedures for maintenance • Rust prevention and painting • Filter maintenance • Periodic operation of emergency or standby equipment Emergency stop Restart Records Maintenance 7-5 ASCEIEPRI Guides 1989 Emergency procedures Revisions Maintenance manual J. EMERGENCY OR ''NEED FOR ASSISTANCE" PROCEDURES Emergency Action Plans for hydro projects are nonnally governed by FERC requirements as outlined in Part 12, Sections 12.20 to 12.25 of CFR 18. These cover conditions, such as floods, fires, and earthquakes, that affect the project facilities and may endanger the lives or property of others. Although those requirements are aimed at maintaining public safety and communications during emergency conditions, other less critical items should be consid- ered for nonemergency conditions. A list of names and phone numbers (plus alternatives) for assistance with electrical problems, mechanical problems, vandalism, and minor medi- cal problems is desirable. K. REVISIONS The operation procedure should be updated six months after startup and as a routine part of the annual maintenance to remove items that prove to be unnecessary and to add new ones. L. MAINTENANCE MANUAL The infonnation needed in the maintenance manual is detennined by the design engineers and equipment suppliers. However, the preparer of the manual must aggressively pursue the designers and equipment suppliers for maintenance infonnation. There cannot be too much maintenance infonnation. The maintenance manual should include: • Specific infonnation covering description, installation, operation, preventive mainte- nance, corrective maintenance, overhaul, lists of parts and spare parts, and an appendix. (A complete parts list and a list of recommended spare parts shall provide all necessary infonnation, including part numbers and catalog item numbers if appli- cable, for identifying parts. Parts or assemblies obtained from another manufacturer and identifying part numbers. The size, capacity, or other characteristics of the part shall be supplied if required for identification.) • Descriptive infonnation consisting of drawings and diagrams, and a physical and func- tional description of the equipment including major assemblies and subassemblies. • Installation infonnation covering preinstallation inspection, installation, calibration, and preparation for operation, both for initial installation and for installation after overhaul. • Operation infonnation including step-by-step procedures for starting, restarting, oper- ating, shutdown, and emergency requirements. The information shall also include per- fonnance specifications and operating limitations. • Maintenance infonnation including step-by-step procedures for inspection, operation checks, troubleshooting, cleaning, lubrication, adjustments, repair, overhaul, disas- sembly, and reassembly of the equipment for proper operation of the equipment. A list of special tools required for maintenance shall be included with the maintenance information. • As-built drawing of the project including all contract wiring, manufacturing, and fabri- cation drawings. • Name and location of the supplier (not manufacturer) of each device and where the device can be repaired or purchased. ASCE/EPRI Guides 1989 7--6 • Requirements for quarterly, semiarmual, and annual maintenance. • Detailed as-built measurements with tolerances of all wear surfaces that can be com- pared and evaluated during subsequent inspections. • When catalogues of standard manufacturer's data are provided, the pertinent sections should be identified. • Brush and tree trimming requirements for transmission lines. M. REFERENCES IEEE Standard 15-1983, "IEEE Guide: Test Procedure for Synchronous Machines." ANSI/IEEE Standard 492-1974, "IEEE Guide for Operation and Maintenance of Hydro- Generators." ANSI/IEEE Standard 43 1974, "IEEE Recommended Practice for Testing Insulation Resistance of Rotating Machinery." ANSI/IEEE Standard 432-1976, "IEEE Guide for Insulation Maintenance for Rotating Electric Machinery (5 hp to less than 10,000 hp)." 7-7 ASCE/EPRl Guides 1989 CHAPTER 8. ENVIRONMENTAL MITIGATION AND FACILITY DESIGN CONTENTS Section Page A. Introduction ................................................................................................................................................. 8-1 B. Impacts on fish ............................................................................................................................................ 8-2 1. Coldwater fish ......................................................................................................................................... 8-2 2. Wannwater fish ....................................................................................................................................... 8-2 3. Migratory fish ......................................................................................................................................... 8-3 4. Upstream fish bypass methods ............................................................................................................... 8-3 5. I>ownstream bypass methods .................................................................................................................. 8-3 6. Mechanical transportation systems ......................................................................................................... 8-3 7. Other guidelines ...................................................................................................................................... 8-3 C. Temperature and water supply considerations ............................................................................................ 8-4 1. Temperature ............................................................................................................................................ 8-4 2. Water supply considerations ................................................................................................................... 8-4 D. Dissolved oxygen ........................................................................................................................................ ~ E. Flow requirements ....................................................................................................................................... 8-6 1. Determining instream flow needs ........................................................................................................... 8-6 2. Providing minimum flows ...................................................................................................................... 8-6 F. Gas bubble disease ...................................................................................................................................... 8-8 G. Monitoring requirements ........................................................................................................................... 8-10 1. Required parameters ............................................................................................................................. 8-10 2. Operational monitoring parameters ...................................................................................................... 8-10 H. Dredging .................................................................................................................................................... 8-10 I. Water level fluctuations ............................................................................................................................. 8-11 1. Reservoirs ............................................................................................................................................. 8-11 2. Tailwaters .............................................................................................................................................. 8-13 J. Aquatic plants, insects, and wildlife ......................................................................................................... 8-13 1. Aquatic plants ....................................................................................................................................... 8-13 2. Insects ................................................................................................................................................... 8-14 3. Wildlife ................................................................................................................................................. 8-14 K.Gravel recruiunent .................................................................................................................................... 8-15 L. References ................................................................................................................................................. S-15 TABLES Table 8-1 Instream flow and habitat quality methods ........................................................................................... S-10 8-2 Summary of the potential environmental effects of dredging and dredged material disposal .............. 8-12 FIGURE Figure 8-1 Six approaches used to determine instream flow recommendations ...................................................... 8-7 ASCE/EPRI Guides 1989 CHAPTER 8. ENVIRONMENTAL MITIGATION AND FACILITY DESIGN This chapter discusses several of the most common environmental issues and presents plan- ning and design guidance in relation to them. A. INTRODUCTION The resolution of environmental issues directly affects the feasibility of hydropower pro- jects. Environmental issues must be addressed to obtain a license for the project, mitigative features often must be designed into the project, and these features must be operated to achieve the environmental goals established for the project. The major environmental impacts of hydropower development are those associated with the actual construction of a new dam and the subsequent inundation of land upstream from the dam if a dam is to be constructed for the first time. For the construction of a new reser- voir, this can be an extremely complex issue. If a dam already exists and a hydro addition is to be made or an existing one refurbished, of course the alternative uses of the upstream land are not at issue. Deep release dams characterize most of the major mainstream impoundments in the United States. Stanford and Ward [ 1979] characterized the general environmental impacts down- stream of such facilities as: 1. Stabilized, armored substrata caused by successive clearwater sluicing and lack of substrate redeposition, which normally occurs during floods 2. A low-amplitude (depressed) thermal regime that is flow dependent 3. Profuse accumulations of algae caused by increases in transparency, nutrients, bed stability, and the absence of sediment or ice scour 4. Reduced species diversity in the macroinvertebrate community, which may be attributed primarily to lack of thermal cues for completion of important life history events such as emergency egg hatching, and timing of maturation 5. Increased macroinvenebrate biomass, often with flow constancy or organic loading from the reservoir. Dams may act as barriers to fish migrating upstream or cause mortality to downstream migrants, which are forced to travel through penstocks and turbines to pass the dam. Releases from dams can also be low in dissolved oxygen (D.O.) and contain high concen- trations of soluble metals and hydrogen sulfide. Fish are also sensitive to water supersatu- rated with dissolved gases, which can result in gas bubble disease. Additional information on the environmental impacts of dams on downstream ecosystems is presented in [Hagen and Roberts, 1973], [Stanford and Ward, 1979], and [Ruane et al., 1986]. Environmental planning Downstream impacts Construction activities themselves cause another class of impacts. Often, the activity that Major issues causes the largest impact is dredging. 8-1 ASCE/EPRI Guides 1989 Fishery impacts Coldwater fish Warmwater fish The environmental issues that are normally the most imponant are discussed in this chapter: • Impacts on fish • Temperature and water supply considerations • Dissolved oxygen • Flow requirements • Gas bubble disease • Monitoring requirements • Dredging • Water-level fluctuations • Aquatic weeds, insects, and wildlife • Gravel recruitment B. IMPACTS ON FISH 1. Coldwater Fish Coldwater resident (nonmigratory) fish typically inhabit rapidly flowing streams at rela- tively high elevations, while most warmwater fish prefer deep, sluggish streams or reser- voirs and lakes. The construction of a reservoir will often tend to reduce coldwater fish habitat and create habitat for warmwater fish. Sometimes. however, such reservoirs ther- mally stratify (see sec. C. I) and create a coldwater pool in the bottom of the reservoir. Stratification of a reservoir can also lead to a two-story fishery. Warmwater fish such as bass will live in the upper elevations and trout will live in the lower elevations. This cold water can then be used to support a coldwater fishery in the tailwater if releases are made from the bonom. Coldwater fish prefer turbulent streamflows. A reservoir may aid these fish in downstream areas by augmenting natural seasonal low flows. However, there is a tradeoff with these releases because the cooler water must be drawn from the lower levels of the reservoir. This water usually has the lowest oxygen levels and might have to be reaerated. 2. Warmwater Fish Many warmwater fish use aquatic plants for cover and eat the insects that grow on the plants. These plants grow at a depth of 3 to 15 meters, depending upon the clarity of reser- voir water. and have a low tolerance to changes in reservoir depth. So the warmwater fish populations will decline if a reservoir's water level fluctuates drastically due to flood con- trol or hydropower requirements. Conversely, a reservoir level that is kept relatively stable for the benefit of fish cover and food will severely limit hydropower storage, with a result- ing loss of energy generation. In addition. most warmwater fish cannot tolerate large changes in reservoir elevation dur- ing their spawning cycles. A maximum fish population naturally occurs in a stable, shallow reservoir. This condition results in large lake evaporation losses, so once again there is a cost to hydropower generation. ASCE/EPRI Guides 1989 8-2 3. Migratory Fish Salmon and related species of migratory (anadromous) fish travel upriver to small streams to spawn, generally in the late fall, winter, or spring. The fingerlings may remain in this general area for up to three years, traveling to the sea in the late spring where they stay for one or more years before returning to their birthplace to spawn. A dam will block this migration completely unless some way is provided to allow the fish to bypass the dam. Bypass facilities must be designed to minimize the delay and physical exertion on the fish. 4. Upstream Fish Bypass Methods Migratory fish Fish passage methods The most common bypass is a fishway, which allows fish to swim through a series of baf-Upstream fles with stillwater bays at each step to allow resting. The water velocity is held below 1.1 m/s, and the facility is designed to accommodate the full anticipated range of tail water and headwater fluctuations. These fishways are sized to pass the largest possible percentage of fish at the least possible cost. Because most species of tropical migratory fish avoid fish ladders, some other method of transportation may have to be used. A comprehensive review of fish ladder design was conducted by Osborne [1985]. 5. Downstream Bypass Methods Even though a large percentage of fish can be safely passed through turbines and spillways, some mortality results. On some river systems several sequential dams can result in signifi- cant loss of young fish migrating downstream. Screens can be used at wrbine intakes to pass fish around the wrbines. In some cases, mechanical transportation systems should be used. 6. Mechanical Transportation Systems Downstream If a dam is very high or fish counts are relatively low, the fish may be transported past the Mechanical dam by mechanical means (locks, elevators, or trucking). The fish are enticed by an attrac· tion current. trapped in a hopper, then transported around the dam and placed in slackwater so that they have sufficient time to recover before resuming their migration. Sometimes, the fish are barged or trucked around a series of dams, thereby minimizing turbine mortali- ty and the time required to pass through many reservoirs, which also contributes to increased mortality. If the fish cannot be bypassed or all spawning areas are flooded (as on the Columbia River), the fish may be trapped and their eggs removed and raised to fingerling size in a hatchery. The fingerlings can be released into the stream or transported downstream past all obstructions. 7. Other Guidelines Several methods are used to pass fish around a dam, including fish ladders, trap and haul, lifts, locks, and cableways. Although the last two methods have been successfully applied, they are usually associated with large dams on large river systems. These methods are dis- cussed in Division II, Part D, "Environmental," of the Conventional GuideUnes (vol. 1). For small hydropower developments, ladders, trap-and-haul, and lift systems are usually 8-3 ASCE!EPRI Guides 1989 Temperature Water supply Multilevel intakes Dissolved oxygen the best methods. Design guidelines are also presented in Division II, Chapter 2, "Waterways." A comprehensive review of fish passage systems is presented by Bell [1986]. C. TEMPERATURE AND WATER SUPPLY CONSIDERATIONS 1. Temperature During the wanner months, the surface waters of a reservoir can become heated. This results in essentially two layers of water in the reservoir. The wanner, and hence less dense, top layer is called the epilimnion. Beneath it is the cooler, more dense bottom layer called the hypolimnion. This phenomenon, the fonnation of the two layers of water, is called thennal stratification. Reservoirs associated with small hydro development may tend to be shallow or have short retention times. These factors tend to reduce the importance of stratification. If maintaining downstream temperature objectives is important and stratification is a major consideration, then care must be taken in designing the hydroturbine intake structure. If the objective is to keep releases as cold as possible for as long as possible, placing the pen- stock entrance as close as possible to the reservoir bottom is all that is required. If the objective calls for wann water in the releases, then the penstock entrance must be placed as high as possible. A multilevel intake allows withdrawals to be made from several depths and allows for blending of the water to achieve the desired temperature in the turbine release. Seldom can a small hydropower project afford to construct a multilevel intake, however. Multilevel intakes are discussed under Division II, Part D, "Environmental," of the Conventional Guidelines. 2. Water Supply Considerations Multiple-use reservoirs used for water supply as well as hydropower, might have problems with algae. Certain blue-green algae can produce undesirable tastes and odors that could adversely affect water intakes. Where taste and odor are a problem, intakes must be placed low enough to avoid the influence of the algae. Generally, depths below the secchi depth are sufficient to avoid algae problems. Sometimes multilevel intakes are used for this purpose. Metals that are insoluble under aerobic conditions might become dissolved under anaerobic conditions. Sometimes it is necessary to place the intake high enough to avoid high con- centrations of metals such as iron and manganese. Another approach to iron and man- ganese control is discussed in the next section. D. DISSOLVED OXYGEN Biological and chemical processes that consume oxygen are at work throughout the reser- voir. In the epilimnion there are also photosynthetic processes that produce oxygen. In addition, the exposure of the surface of the reservoir to the atmosphere naturally replenish- es the oxygen supply. ASCE/EPRI Guides 1989 8-4 In the hypolimnion, no oxygen-producing processes are at work, but oxygen-consuming processes continue to be active. The epilimnion isolates the hypolimnion from oxygen replenishing processes. The result is that the hypolimnetic water in stratified reservoirs often contains depressed oxygen concentrations. Sometimes the oxygen concentrations approach zero. Anoxic decomposition of bottom sediments sometimes results in the pro- duction of hydrogen sulfide, which even in small concentrations is toxic to aquatic life. New reservoirs are particularly susceptible to oxygen depletion in ways that can cause a catastrophic break in the life cycle of resident biota. Therefore, the land that is to be inun- dated by a reservoir is often cleared of most of its vegetative matter, including grasses. Organic material remaining when the reservoir is filled may rot quickly, releasing large quantities of nitrogen and phosphorus into the water. This may cause severe but temporary instability in a reservoir with a large volume of water exchange because nutrients will lead to a quick increase in aquatic weeds, plants, phytoplankton, and fish. If a reservoir has a low exchange ratio, all existing dissolved oxygen (D.O.) may be consumed by bacteria, leading to the possible killing of most or all of the resident fish population. This break in the population life cycle might require years of concerted effort to rectify. The bottom of a reservoir may contain oxidized metals such as iron and manganese. In the Dissolved oxidized state, which is maintained by the presence of the oxygen, these metals are insolu-metals ble. However, when the oxygen disappears, the metals can be reduced to their soluble fonn. Because of depressed oxygen levels in the reservoir, water released to the stream below the Low D.O. project can be low in D.O. and can severely affect downstream aquatic life. In addition, downstream iron and manganese concentrations can also be high in the turbine releases. Because of the long period of time (generally days) needed to reoxidize the iron and, especially, the man- ganese, these species can adversely affect downstream water supplies. In some cases, they can be so high that they too can affect the stream aquatic life. If iron and manganese are a problem, they can only be controlled by aeration activities in Reservoir the reservoir or through the use of a multilevel intake. Much more common is simply the aeration presence of low D.O. levels that sometimes can be improved by using the turbine for aera- tion. Both turbine aeration and reservoir aeration will be discussed beginning with turbine Turbine aeration. aeration Releases from power-generating facilities can be reaerated in several ways. Systems include turbine aeration in which the hydroturbine is modified to draw in atmospheric air and mix it with the turbine discharge. Typical D.O. increases for this method are from 1 to 3 mg/L. Compressed-air systems have also been used to blow air into the penstock or draft tube. Theoretically, the turbine discharges can be saturated using this method. Aeration in the reservoir using either compressed air or high-purity oxygen is a third method. Division II, part D of the Conventional Guidelines discusses the design of these metlx>ds in detaiL The Tennessee Valley Authority [1981, 1983, 1985, and 1987] and Bohac et al. [1983] dis- cuss numerous methods for improving D.O. in releases from hydropower projects. 8-5 ASCEJEPRI Guides 1989 Minimum flow In stream flow needs Providing minimum flows E. FLOW REQUIREMENTS Some hydro projects might be faced with providing continuous minimum streamflows downstream. For projects at which the turbines are operated continuously to provide baseload power, providing minimum flow is not generally a problem. However, when pro- jects are used to supply power only during the peak demand period of the day, there can be extended periods of time in which there is little or no flow. 1. Determining Instream Flow Needs Instream flow needs may have to be established for navigation, recreation, assimilative capacity, and fish and aquatic life. Navigation and recreational flows are determined by hydraulic considerations to provide minimum depths at various control sections of the river downstream from the dam. A set of rating curves can generally be developed for a range of discharges to determine the minimum flow required to meet the minimum depth criteria. Assimilative capacity considerations require that downstream wastewater discharges do not cause violation of stream water quality standards. These flows are often determined by water quality modeling. Most state water quality regulatory agencies that specify the minimum flow needs use the QUAL2 streamwater quality model distributed by the Environmental Protection Agency [Brown and Barnwell, 1985]. The most difficult and controversial flow needs to assess generally deal with the flows needed for aquatic biota. The methods used to assess this category are numerous and com- plex, and usually require significant quantities of transect, substrate, flow, and aquatic species data. A review of several instream flow analysis is presented by Loar and Sale [1981] and by Morhardt and Altouney [1986]. Minimum flows for aquatic life are generally determined in one of six ways as illustrated on figure 8-1. Approximately 75 instream flow and aquatic habitat methods were investigated by EA Engineering, Science, and Technology, Inc. [1986]. Table 8-1lists 54 of the methods and the species for which the minimum flows are provided. It was concluded that the different methods when applied to the same stream may produce different results. At this time, it is difficult to conclude which of the methods are the more suitable. The difficulty is that few of the methods have been tested to determine whether the type of habitat and standing crop of organisms that they predict actually occurs when the specified flows are provided. More detail on how to determine minimum flows and systems to provide them is presented in division II, part D of the Conventional Guidelines. 2. Providing Minimum Flows In cases where minimum flows are provided at a multiturbine installation, perhaps the best approach is to size at least one turbine specifically to provide the minimum flow. In fact, one of the applications of small hydropower technology is to provide minimum flows at conventional hydropower facilities used for peak power production. ASCE/EPRI Guides 1989 8-6 -a • -j Traditional Methods a. Basin Variables b. Average Discharge c. Discharge Exceedence c: ·;; 0 en d. ... • -• e ... ~ Slope Recommended Aow • 01 ~ ~ • 0 >-<(II.. Recomended Aow • () c: 0 -a • ~ ~ >C II..~ Incremental/Habit at Quality Methods Un transformed e. Biologically Transformed f. Hydraulic Variables Hydraulic Variables Re lot iva = Point -a 0 a:j on 'l: u Curve 3::: • -.. -::;; c ~ :i c 3::::::1 iii Reconvnended Flow Recommended Flow Six approaches used to determine instreom flow recommendations. Recommended Flow Multiple Biologically Transformed Variables Selected Value / Recommended Flow o. As size or some other physico I choroc teri stic of the drainage basin increases, the minimum recommended flow also increases. (In this example, the policy sets different relationships between basin size and flow for sprinQ and summer.) b. The recommended flow is o fixed percentage of the overage flow. c. The recoiMiended flow is equal to the flow natural I y exceeded a fixed percentage of the time. d. A measurable physical variable is plotted as o function of flow, and the location of o break point on the curve determines the recommended flow. e. A nondirnensional suitability index based on physical hydraulic variables is plotted as o function of flow, and the peak, o break point, or some other feature of the curve is used as the flow criterion. f. The output of o predictive model of o measurable variable ( in this case Binns' Habitat Quality Index, which equals calculated standing crop) is plotted against f I ow, and the recommended flow is determined from a break point or some other feature of the curve. Figure S-1.-Six approaches used to determine instream flow recommendations. [EA, 1986]. 8-7 ASCE/EPRI Guides 1989 Gas bubble disease Super- saturation Spillway and intake design Aeration Other ways of providing minimum flows include sluicing and providing a downstream reregulating structure. Sluicing was previously described as a way to aerate the water. The use of reregulating structures, which are more common to conventional hydropower instal- lations, are discussed in division II, part D of the Conventional Guidelines. The Tennessee Valley Authority [1983, 1984, 1985, and 1987] presents several examples of alternative structures and systems to provide minimum flows. F. GAS BUBBLE DISEASE Gas bubble disease results when fish are subjected to water supersaturated with nitrogen, oxygen, and argon. The disease occurs when dissolved gases come out of solution in the blood of fish. The air bubbles cause embolisms resulting in damage to organs, especially the eyes. Often the embolisms result in death. An excellent survey of the literature on gas bubble disease is presented by Fickeisen et al. [ 1980]. A general rule of thumb for the supersaturation levels at which acute gas bubble disease can occur is 110 percent total gas pressure. The concentration of all three gases is consid- ered simultaneously in computing total gas pressure. Supersaturated conditions arise most often in spilling water. In this case, the water may trap air when it plunges to great depth at the end of a spillway. The added depth causes more of the gases to dissolve than would dissolve at the surface. When the water rises from depth to the surface, the saturation concentration is less than it is at the bottom of the plunge; the water is, therefore, supersaturated and the gases begin to come out of solution. Supersaturation is often avoided by installing flip lips at the bottom of spillways to deflect the water into the air or shoot it out horizontally from the spillway rather than let it plunge to great depth. In cases where hydroturbines are to be installed on an existing nonpower project, release of the water through the turbines rather than over the spillway would reduce the potential for gas bubble disease. The turbine intakes must be properly designed so that they do not entrain air. However, sometimes intakes are placed so deep in the reser- voir that the reservoir water is saturated with dissolved gas. If the intakes are very deep, water is released to the tailrace and exposed to much lower pressure and higher tempera- ture than in the reservoir. This can result in releases supersaturated with dissolved gas and the potential for gas bubble disease. More detail is presented in division II, part D of the Conventional Guidelines. In normal turbine operation, supersaturation, and hence gas bubble disease, is not generally a problem. Much experience exists in raising the D.O. from 0 or 1 mg/L to 3 or 4 mg/L on tributary dams along the Tennessee River without total gas pressures reaching 110 percent or the observance of gas bubble disease [TVA, 1981, 1983, and 1984]. However, aeration can theoretically cause supersaturation. If D.O. levels of 6 mg/L or more were achieved using air, supersaturation might well exceed 110 percent total gas pressure. If excessive supersaturation is suspected using air to reaerate the water, high-purity oxygen should be considered for use. The use of oxygen would eliminate the additional dissolution of nitro- gen that occurs when air is used. ASCE/EPRI Guides 1989 Table 8-1.-Instream flow and habitat quality methods. [EA, 1986]. Name of method Wetted Perimeter Method Diagrammatic Mapping Method Wyoming Habitat Quality Index USFWS Instream Aow Incremental Methodology Spawning and Rearing Discharge USFS Region 4 Method USFWS Habitat Suitability Index Model USFWS Habitat Suitability Index Model USFWS Habitat Suitability Index Model USFWS Habitat Suitability Index Model USFWS Habitat Suitability Index Model Utah Water Records Methodology USFWS Habitat Suitability Index Model USFWS Habitat Suitability Index Model Minimum Stream Aows for Fish USFWS Habitat Suitability Index Model USFWS New England Aow Recommendation Policy Habitat Suitability in Prairie Streams Habitat Suitability Index Model Discriminant Habitat Analysis USFWS Habitat Suitability Index Model USFWS Habitat Suitability Index Model USFWS IFG4 Hydraulic Simulation Model USFWS Water Surface Profile Model USFWS Habitat Model Montana DFWP Wetted Perimeter Method Habitat Needs for Salmonid Rearing Stream Aow Requirements for Salmonids Northern Great Plains Resource Program Method Spawning Habitat Using Watershed and Channel USFWS Habitat Suitability Index Model Fish Habitat Index Using Geomorphic Parameters Habitat Based Georgia Standing Crop Models USFWS Habitat Suitability Index Model One Flow Method USFWS Habitat Suitability Index Model USFWS Habitat Suitability Index Model USFWS Habitat Suitability Index Model USFWS Region 6 Single Transect Method Washington Basin Variables Method Washington Toe-Width Method Washington One-Variable Regression Method Riparian Strip Width Model 8-9 Species Salmonids Soho salmon Trout All species Anadromous salmon Trout Bigmouth buffalo Longnose sucker Common carp Slough darter Longnose dace Trout Warmouth Cutthroat trout Trout Northern pike All species Eight warmwater species Spotted bass Cutthroat trout Creek chub Coho salmon All species All species Coho salmon Salmonids All species Steelhead Alewife/blueback herring All species Nine species Brook trout Anadromous salmonids Black bullhead Bluegill Green sunfish Salmonids Steelhead Steelhead Salmon Vegetation ASCE/EPRI Guides 1989 Monitoring Dredging 'Thble 8-1.-Instream ftow and habitat quality methods. [EA, 1986].-Continued Name of method Montana Method Oregon Usable Width Method USFWS Habitat Suitability Index Model USFWS Habitat Suitability Index Model USFWS Habitat Suitability Index Model USFWS Habitat Suitability Index Model California Instream Flow Method R2-CROSS-8l Sag Tape Method WRR1 Trout Cover Rating Method Idaho Instream Flow Method Midwestern Trout Standing Crop Species All species Salmonids Blacknose dace Common shiner Fallfish Atlantic salmon Salmonids Trout All species Trout G. MONITORING REQUIREMENTS Monitoring at the project is determined by the requirements specified in the project license and parameters needed for operational control. 1. Required Parameters Often, the project is required to monitor and report values for flow, D.O. and temperature in the tailrace. A continuous recording of flow is generally required. Typical oxygen and temper- ature requirements might include reporting minimum and maximum daily values. These requirements can generally be best met by providing continuous D.O. and temperature moni- toring equipment. In cases where fish screens are used, reporting the head loss across the fishscreen is required to ensure that the fishscreen has operated properly. Flow monitoring of the automatic fish bypass systems might also be required to similarly ensure proper operation of that system. 2. Operational Monitoring Parameters To satisfactorily operate some of the environmental mitigation facilities, it might be necessary to monitor other functions. The turbine inlet D.O. and temperature might be monitored to activate the aeration system or change the withdrawal level in an intake structure. The temperature of a fish bypass system might have to be monitored and regulated to ensure that it meets the preferences of the fish. Fish attraction flows to ladders must be monitored and adjusted as water levels change. H. DREDGING Construction of a new dam or retrofitting an existing dam may require dredging. In some retrofit applications, dredging to reclaim lost storage facilities might also be considered. The ASCE!EPRI Guides 1989 8-10 six major environmental concerns about dredging are summarized in table S-2. Measures suggested by Loar et al. [ 1980], which can be used to reduce the severity of the impacts or in some cases eliminate them, include: • Avoid dredging during periods of high biological productivity (usually spring through midsummer). • Minimize turbidity and downstream siltation, especially if: o The impoundment is small and a large ponion of it will be dredged o Highly contaminated sediments are present o Dredging is not conducted during periods of low productivity or sensitive life stageS/species are present o Dredging does not coincide with the period of high sediment loading to the river. • Prevent downstream siltation if threatened or endangered mussel species inhabit areas below the dam. • Design confined upland disposal areas to minimize the levels of suspended solids in the effluent returning to the water body. • Avoid the disposal of dredged material in wetland areas. • Obtain information on historical land use in the watershed, including present industri- al and municipal effluent sources and water quality data on the watershed. If no prior data on the chemical composition of the sediments exist, then an inventory of the sed- iments to be dredged should be considered. Bulk sediment analysis, however, should not be used to predict the impacts of the proposed dredging and disposal operations. • Assess chemical changes in the water column before dredging using the Elutriate Test and compare the results with appropriate water quality criteria. If the results indicate that contaminants will be released to the water column during dredging, then: o Bioassays should be considered using sensitive species that inhabit the site o An evaluation of bioaccumulation potential should be conducted I. WATER LEVEL FLUCTUATIONS 1. Reservoirs Reservoir pool level fluctuations caused by operation of the hydropower units can cause physical, chemical, and biological impacts in the reservoir. Hildebrand [ 1980] has reported that physical and chemical impacts can include: • Resuspension and redistribution of bed and bank sediment • Leaching of soluble matter from sediment in the littoral zone as water moves into and out of the interstices (bank storage) in response to water level fluctuations • Changes in (a) sediment and nutrient retention (trap efficiency) of the impoundment because of hydroimposed changes in circulation patterns and hydraulic efficiency, and (b) water quality, which is coupled to circulation pattern and hydraulic efficiency In addition, biological impacts can include: • Habitat destruction resulting in partial or total loss of organisms • Changes in habitat quality resulting in reduced standing crop and production • Shifts in species diversity Water levels 8-11 ASCEIEPRI Guides 1989 Table ~2. -Summary of the potential environmental effects of dredging and dredged material disposal. [Loar et al, 1980) ). Physical/chemical effect 1. High suspended matter and high turbidity 2. Low dissolved oxygen 3. High concenrrations of inorganic plant nutrients (N.P) 4.Highconcenttations of toxic contaminants 5. Silt deposition below dam 6. Alteration of substratum ASCE/EPRI Guides 1989 Causes Resuspension of bottom sediments Inadequate disposal Fine-grained sediments ~ consumption by oxidation of resuspended organic matter and reduced chemical species Release of inorganic nutrients from dredged sediment and interstitial warer Release from interstitial water and dissolution/ desorption from dredged sediments Resuspension and trans- port of bottom sediments Erosion/runoff or overflow from disposal site Removal of sediments 8-12 Resultant biological effects Reduced primary productivity Disorientation of visual predators Death or stress due to clogging of gills (fish) and feeding structures (mussels, zooplankton) Death or stress to fish, plankton and benthic macroinvertebrates Increased algal and bacterial productivity Short-term: Death or stress to exposed biota Long -term: Entry into and accumulation in food chains (heavy metals, chlorinated hydrocarbons) Destruction of fish spawning areas and habitats Smothering of mussels and other benthic invertebrates, benthic algae, submerged macrophytes, fish eggs and larvae Shifts in species composition, distribution and abundance Removal of benthic invertebrates Shifts in species composition, distribution, and abundance Mitigation of the effects of water level fluctuation must be done through operation of the project. No structures or systems can be designed into the project. To aid in developing guidelines for reservoir operation to protect reservoir fisheries, Ploskey et al. [ 1984] used multiple-regression analyses to relate fish variables to seasonal hydrologic variables. Two kinds of hydropower facilities were examined, storage and mainstream. 2. Tailwaters Rapid turbine shutdown can result in the stranding of juvenile fish on shallow parts of the streambed that dry when the turbines are not operating or are operating only to provide for minimum flow in the river. Therefore, maximum downramping rates are sometimes devel-Tailwater oped for the project The downramping rates provide for the maximum rate of tailwater comments drop so that the fish have adequate time to return to deeper pools in the main river channel before the shallow areas are dry and strand the fish. Because the rates depend on the streambed morphology, fish species, fry emergence time, and fish growth, they must be developed on a case-by-case basis. Some reported downramping rates range from 1 to 6 in/hr as measured in the dam tailrace during critical portions of the year [Olson and Metzgar, 1987]. Fish eggs are not mobile, and serious losses to year classes can occur when eggs are dewatered [Cross, 1986]. J. AQUATIC PLANTS, INSECTS, AND WILDUFE 1. Aquatic Plants Aquatic plants can cause significant problems in reservoirs. The plants can choke water- ways and interfere with recreational activities, especially boating. Plants can also con- tribute to substantial oxygen demand in reservoirs. Aquatic plants or macrophytes can float on the surface, be rooted in the reservoir bottom, and grow out of the water. They can grow barely submerged or completely under water. Plants can be controlled with chemicals, mechanical methods, biological controls, or reser- voir operation. Once a reservoir becomes infested with plants, eradication is difficult; man- agement of the plants by controlling them in selected locations generally becomes the pri- mary objective. Physical control methods consist of cutting or pulling plants to reduce their growth or den- sity. Recent advances have been made in floating mechanical harvesters. Other physical methods include drawing the reservoir down at strategic times to freeze the roots of the plants. Light-attenuation methods, such as using colored dyes and sediment covers to reduce the availability of nutrients, have also been used [Moore, 1987]. Herbicides have been widely and successfully used for many years, but proper selection and application of the chemicals is paramount to their success. Hansen et al. [1984], have prepared an excellent reference on aquatic plants and the selection and use of herbicides. Addition of chemicals such as alum to inactivate phosphorus is another chemical control method [Mesner and Narf, 1987]. Weeds and algae 8-13 ASCEIEPRI Guides 1989 Insects Wildlife Biological control is the newest method. It involves the introduction of predator organisms into the reservoir. One of the most JX>pular species is the sterile grass carp. The carp can be effective but can eat other fish food organisms if the reservoir is overstocked [Moore, 1987]. 2. Insects The construction of a reservoir in tropical or subtropical areas may encourage the breeding of certain dangerous insect pests. These pests may have a profound impact on the local JX>pulace, to the point of shortening life spans considerably. Such infestations must be anticipated and dealt with before and during project construction. If the problem is ignored, or detected only after the project is built, much unnecessary suffering and expense will result It is always easier to prevent the introduction or spreading of insect pests than it is to eradicate them. Malaria and yellow fever may be transmitted by species of mosquito that require shallow, stable JXX>ls to breed. The construction of a reservoir in an area of rugged topography can create many linear kilometers of narrow backwater marshes, which are ideal for mosquito breeding. The magnitude of mosquito breeding has been found to be directly proportional to the water area covered by phreatophytes. If a reservoir is large, plant or insect control mea- sures may require impractically large storage releases, and stagnant areas along the lake must then be sprayed. Most mosquito breeding areas can be cleared by changing reservoir elevation at a rate of about 0.3 meters per week, which is too small a variation to harm fish. The Tennessee Valley Authority has developed unusual reservoir rule curves that allow weekly fluctua- tions of JXX>llevels during the mosquito breeding season. Other dangerous insect pests may require carefully planned and imaginative control mea- sures, particularly in developing countries. For example, the blackfly (Simulum Damnosum) breeds in rapids and inflicts river blindness (Onchoerciasis). 1be construction of a reservoir or irrigation scheme will naturally eradicate the insects where rapids or fast- moving waters are submerged. The Bilharzia (11ng) snail may be controlled by longer- cycle reservoir fluctuations, or may be progressively displaced over an extended period by the larger Marisa Comuarietis snail. 3. Wildlife Long before the construction of any water resources project, responsible agencies must conduct a comprehensive biotic inventory both in the area of the reservoir and in possible mitigation areas. Sometimes, threatened or endangered species must be moved and provid- ed mitigative habitat of equal value to the one they previously occupied. Habitat loss for nonendangered or threatened species must be compensated for by improving nonimpound- ed sites. Ducks, geese, and other migrating waterfowl require large, shallow lakes with sufficient food plants to support them and their small prey. A new lake provides a resting and nesting ASCE/EPRI Guides 1989 8-14 area for migrating waterfowl and inundates brushy areas along streams that serve as home to such species as deer, bear, and squirrel. However, the draining or submergence of flyway habitat confuses and hampers migration. It may be possible to flood low marshy areas near natural flyways to replace those areas inundated by a reservoir, if land costs are not pro- hibitive. Reestablishing the original habitat balance may take several years in a mitigation area. K. GRAVEL RECRUITMENT The construction of a dam reduces the renewal of sand and gravel in the tailwaters below the dam. Sands and gravels washed into the reservoir are deposited. High flows, especially during floods, continue to scour the sands and gravels below the dam, but the dam prevents redeposition. Because sand and gravel are important repositories for eggs, their absence in the tailwaters can impair fish and aquatic insect reproduction. This problem has been mitigated at several dams (e.g., Shasta Dam in California) by haul- ing sand and gravel from other sources and placing them in the tail waters. L. REFERENCES Bell, M.C., Fisheries Handbook of Engineering RequiremenlS and Biological Data, U.S. Army Corps of Engineers, Nonh Pacific Division, Portland, Oregon, 1986. Bohac, C.E., Boyd, J.W., Harshbarger, E.D., and Lewis, A.R., Techniques for Reaeration of Hydropower Releases, Technical Repon E-83-5, prepared by Tennessee Valley Authority for the U.S. Army Engineer Waterways Experiment Station, Vicksburg, Mississippi, 1983. Brown, L.C., and Barnwell, T.O., Jr., Computer Program Documentation for the Enhanced Stream Water Quality Model QUAL2, Environmental Protection Agency, EPN60013-85/065, Athens, Georgia, 1985. Cross, P.O., Darling, J., Dos Santos, 1., and Bradshaw, W., "Lower Flathead System Fisheries Study," Annual Reports, Bonneville Power Administration, Portland, Oregon, 1986. EA Engineering, Science, and Thchnology, Inc., "Instream Flow Methodologies" Research Project 2194-2, EPRI, Palo Alto, California, 1986. Fickeisen, D.H., Schneider, M.I., and Wedemeyer, G.A., "Gas Bubble Disease," Transactions Am. Fish Soc., vol. 109, p. 657, 1980. Hagen, R.J., and Robens, E.B., "Ecological Impacts of Water Storage and Diversion Projects," Environmental Quality and Water Development, Goldman, C.R., McEvoy, 1., and Richardson, P.J., editors, W.H. Freeman, San Francisco, 1973. Hansen, G.W., Oliver, F.E., and Otto, N.E., Herbicide Manual, U.S. Depanment of the Interior, Bureau of Reclamation, Denver, Colorado, 1984. Hildebrand, S.G., editor, "Analysis of Environmental Issues Related to Small-Scale Hydroelectric Development, III Water Level Fluctuation," ORNI./fM-7453, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 1980. Sand and gravel 8-15 ASCE/EPRI Guides 1989 Loar, J.M., Dye, L.L., Turner, R.R., and Hildebrand, S.G., "Analysis of Environmental Issues Related to Small- Scale Hydroelectric Development, I Dredging," ORNL/fM-7228, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 1980. Loar, J.M., and Sale, M.J., "Analysis of Environmental Issues Related to Small-Scale Hydroelectric Development, V Instream Flow Needs for Fishery Resource," ORNLtrM-7861, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 1981. Mesner, N., and Narf, R., "Alum Injection into Sediments for Phosphorus Inactivation and Macrophyte Control," Lake and Reservoir Management, vol. 3, North American Lake Management Society, Washington, D.C., 1987. Moore, M.L., NALMS Management Guide for Lakes and Reservoirs, North America Lake Management Society, Washington, D.C., 1987. Morhardt, J.E., and Altouney, E., "Instream Flow Requirement Below Reservoirs: Conclusions from the EPRI Study," Proceedings, Int. Symp. on Applied Lake and Watersheds Managements, November 13-16, 1985, Lake Geneva, Wisconsin, North American Lake Management Society, Merrifield, Virginia, 1986. Olson, F.W. and Metzgar, R.G., "Downramping Regime for Power Operations to Minimize Stranding of Salmonid Fry in the Sultan River," Proceedings, Waterpower '87, ASCE, New York, 1987. Orsborne, J., New Concepts in Fish Ladder Design (Four Volumes), Bonneville Power Administration, Project 82-14, Portland, Oregon, 1985. Ploskey, G.R., Nestler, J.M., and Aggus, L.R., Effects of Water Level and Hydrology on Fisheries in Hydropower Storage, Hydropower Mainstream, and Flood Control Reservoirs, Tech. Report E-84-8, Dept. of the Army, U.S. Army Corps of Engineers (Available from NTIS), 1984. Ruane, R.J., Bohac, C.E., Seawell, W.M., and Shane, R.M., "Improving the Downstream Environment by Reservoir Release Modifications," Proceedings, Reservoir Fisheries Management: Strategies for the '80s, So. Div. Am. Fish Soc., Bethesda, Maryland, 1986. Stanford, J.A., and Ward, J.V., editors, "Stream Regulation in North America," The Ecology of Regulated Streams, Plenum Press, New York, 1979. TVA (Tennessee Valley Authority), "Improving Reservoir Releases," TVA/ONR/WR-82/6, Knoxville, Tennessee, 1981. TVA, "Improving Reservoir Releases,"TVA/ONR/WR-83/10, Knoxville, Tennessee, 1983. TVA, "Improving ReservoirReleases,"TVA/ONRIA&WR-84/27, Knoxville, Tennessee, 1984. TVA, "Feasibility Report Tims/Ford/Elk River Minimum Flows," TVA/ONR/A&WR-85/22, Knoxville, Tennessee, 1985. TVA, "Improving Reservoir Releases," TVA/ONR/A&WR-87/33, Table I-H.2, Knoxville, Tennessee, 1987. ASCE/EPRI Guides 1989 8-16 CHAPTER 9. INSTITUTIONAL ISSUES CONTENTS Section Page A. FERC licensing ........................................................................................................................................... 9-1 B. Consultation process ................................................................................................................................... 9-1 1. Federal agencies .................................................................................................................................... 9-2 2. State agencies ........................................................................................................................................ 9-3 C. Legislation relevant to small-scale hydro development. ............................................................................. 9-3 1. The National Environmental Policy Act .............................................................................................. 9-3 a. NEPA requirements ......................................................................................................................... 9-3 b. Environmental impact statements .................................................................................................... 9-3 2. The Endangered Species Act ............................................................................................................... 9-3 3. The Wilderness Act .............................................................................................................................. 9-4 4. The Wild and Scenic Rivers Act .......................................................................................................... 9-4 5. The Fish and Wildlife Coordination Act .............................................................................................. 9-4 6. The Oean Air Act ................................................................................................................................ 9-4 7. The Public Utility Regulatory Policy Act of 1978 ............................................................................... 9-4 a. Title II .............................................................................................................................................. 9-4 b. Title IV ............................................................................................................................................. 9-5 8. The Oean Water Act ............................................................................................................................ 9-5 9. The Federal Power Act. ........................................................................................................................ 9-5 10. The Elecoic Consumers Protection Act of 1986 ................................................................................. 9-5 II. The Heritage Conservation Act of 1963 .............................................................................................. 9-6 12. The Federal Water Projects Recreation Act of 1965 ........................................................................... 9-6 13. Historic Preservation Acts .................................................................................................................... 9-6 14. The National Trails System Act of 1968 .............................................................................................. 9-6 15. The Coastal Zone Management Act of 1972 ....................................................................................... 9-7 16. Public and Indian lands ........................................................................................................................ 9-7 17. Navigation and flood control ............................................................................................................... 9-7 D. Cumulative impacts ..................................................................................................................................... 9-7 E. Reference ..................................................................................................................................................... 9-7 ASCE/EPRI Guides 1989 CHAPTER 9. INSTITUTIONAL ISSUES A. FERC UCENSING Before construction of a power project can begin in the United States. the applicant must obtain a license from the Federal Energy Regulatory Commission (FERC). FERC has jurisdiction if the project is located on a navigable river, affects interstate or foreign com- merce, uses federal lands, or uses surplus water from a federally owned dam or other facil- ity (canal, conduit, etc.). FERC regulations are published in the Code of Federal Regulations No. 18 (CFR 18), and all changes to the regulations are published in the Federal Register. Because CFR 18 is only published annually, it is important to check for any recent rule changes in the Federal Register. The best source of this information is the appropriate division within FERC. If it is determined that a license is required, the application can take several forms. The license application requirements are somewhat different in each case. The alternatives are: License requirements 1. An application for an exemption from licensing meeting these requirements: Exemptions • Small conduit hydro facility (15 MW or less) which uses a man-made conduit operated primarily for the distribution of water • Small hydro project (5 MW or less) situated on nonfederalland developed by the owner of the real property interests of the site 2. An application for license, short-form (5 MW or less). 3. An application for a license for a major project at a existing dam -for power plants greater than 5 megawatts. 4. An application for a license for a major project -for new construction or major modification proposed for more than 5 megawatts. A developer may also obtain a preliminary permit that is a study authorization. A permit is Study not a prerequisite to a license application, but does give the developer the exclusive right to authorization file a license application before the term of the permit expires (usually 3 years). Virtually all new nonfederal hydropower construction falls under the jurisdiction of FERC. FERC requires applicants to contact appropriate agencies and perform the required studies before the preparation and submittal of an exemption or license development application. B. CONSULTATION PROCESS The three-stage consultation process described by FERC [1985] is as follows: During the first stage, applicants are required to contact all appropriate agencies and pro- vide each of them with specific, detailed information, to the extent available, concerning the project. This information includes maps, engineering design, operational mode, affect- ed environmental and mitigation, and streamflow data. Applicants should seek the advice of the agency regarding potential impacts and what studies may be necessary to assess the effects of the project on the area's natural and socio-economic resources of the area. Consultation First stage 9-1 ASCE!EPRI Guides 1989 Second stage Third stage Federal agencies During the second stage of consultation, applicants must perform all reasonable studies necessary for FERC to make an informed decision regarding the merits of the application. Studies must be conducted before filing an application if the results: ( l) would influence the economic or technical feasibility of the project, (2) are needed to determine the design or location or project feasibility, (3) are needed to determine the impacts of the project on important natural or cultural resources, (4) are necessary to determine suitable mitigation, or (5) are necessary to minimize impacts to a significant resource. The results of any neces- sary studies must be provided to each agency along with a draft application. Applicants must respond in the draft application to any comments and recommendations made by agencies during the initial stage. Applicants are required to provide consulted agencies either 30 days or 60 days, depending on the type of application, to analyze and respond to the applicant's plans of development. FERC has determined that, in regard to exemption applications for small hydroelectric power projects, specified federal and state fish and wildlife agencies have the exclusive authority and responsibility for protecting fish and wildlife resources. Therefore, these agencies must determine which studies concerning fish and wildlife resources must be completed before they can review such applications. If the applicant disagrees with the agency requirements, only FERC has authority to resolve the differences. During the third stage of consultation, the application is filed with FERC and served to each of the agencies consulted. Any subsequent revision, amendment, or supplement of an application must also be provided to each agency consulted. Documentation that the requirements of all three stages of the consultation process have been satisfied must be included in the application, as well as any agency letters containing comments, recommen- dations, or terms and conditions. If the appropriate agencies waive compliance with any requirement, the applicant may omit compliance with that requirement provided the application includes an explanation of the circumstances of the waiver. When the applicant begins to prepare a license, FERC requires consultation with local, state, and federal agencies that may be affected by the project. Agencies that may have to be consulted in the FERC prelicensing process are listed below: 1. Federal Agencies • United States Fish and Wildlife Service regional offices • Environmental Protection Agency regional offices • River basin commissions • Corps of Engineers district office • National Marine Fisheries Service regional directors • Department of the Interior regional environmental officer • Department of the Interior, Bureau of Reclamation • U.S. Forest Service • U.S. Bureau of Land Management ASCE/EPRI Guides 1989 9-2 2. State Agencies • Water quality (agencies with approved NPDES permit program) • Water rights • Environmental quality • Dam safety • Mill Act provisions • Public utility regulation • Energy regulation • Resource development • Fish and wildlife • Recreation • Cultural resources C. LEGISLATION RELEVANT TO SMALL-SCALE HYDRO DEVELOPMENT 1. The National Environmental Policy Act (NEPA) a. NEPA Requirements.-Section 102, pan C of NEPA requires the writing of a compre- hensive environmental impact statement (EIS) by any entity considering the construction of a project that would "significantly affect the quality of the human environment." NEPA also requires that all agencies with legal jurisdiction or relevant expertise be consulted with regards to the construction of a project. FERC has adopted NEPA guidelines and regulations for the writing of an EIS and general- ly requires the submission of an EIS for any project with an installed capacity of greater than 1.5 megawatts. An environmental assessment will be completed and a Finding of No Significant Impact (FONSI) will generally be filed on smaller projects if appropriate. State agencies Legislation NEPA b. Environmental Impact Statements. -The key items of an environmental impact state-EIS ment are as follows: • A description of the proposed project and alternatives • A description of the existing environment • The environmental impact of the proposed project and alternatives • Measures to prevent, reduce, or offset impacts • A study of the "tradeoffs" between local shon-term impacts and the maintenance and enhancement of long-term productivity After a draft EIS has been reviewed and commented on by all interested agencies, the fmal EIS must include an additional section addressing the problems and objections raised by such review. This final EIS must then be fl.led with the Environmental Protection Agency. 2. The Endangered Species Act This act is designed to protect the habitat of endangered and threatened species. The appli- cant is required to obtain a list of endangered and threatened species from the U.S. Fish and Wildlife Service (FWS). The applicant must provide the FWS with a biological assess- Endangered species 9-3 ASCE/EPRI Guides 1989 Wilderness Wild and scenic rivers Fish and wildlife Clean air PURPA Buy from small developers ment. and the FWS will detennine if there is an impact. Small hydropower projects can sometimes receive an exemption if the applicant can show that all endangered species in the vicinity of the project shall not suffer adverse impacts as a result of the construction or operation of the project. 3. The Wilderness Act The Wilderness Act (Public Law 88-577) established the National Wilderness Preservation Program. It is designed to protect and manage undeveloped federal land to preserve its nat- ural state. The Department of Agriculture and the Department of the Interior may establish such areas. PERC cannot grant any kind of license in a wilderness area. 4. The Wild and Scenic Rivers Act The Wild and Scenic Rivers Act protects and preserves certain rivers in their natural, free- flowing state. PERC may not license any project that would be located on or would direct- ly affect any river in these programs or under study for inclusion in these programs. S. The Fish and Wildlife Coordination Act This act directs that wildlife conservation programs be coordinated with and set on an equal footing with other features of water resource development programs. All federal and state agencies will consider the impacts of their programs on fish and wildlife. Agencies with an interest in wildlife conservation include the U.S. Fish and Wildlife Service and state conservation agencies. If the project will impact anadromous, estuarine, or marine fish resources, the National Marine Fisheries Service must be consulted. These agencies can recommend fish passage facilities, fish hatcheries, or wildlife mitigation measures at hydropower projects. 6. The Clean Air Act This act requires entities that produce point sources of pollution to obtain pennits from designated state air quality agencies or from the EPA. No significant deterioration of air quality is allowed in designated areas, such as wilderness areas or national parks. The greatest impact that hydropower will have upon clean air is during construction activi- ties that may raise dust or cause localized chemical spills and evaporation. 7. The Public Utility Regulatory Policy Act of 1978 (PURPA) The purpose of this act is to encourage the conservation of electric energy and to create a program for the efficient exploitation of our country's hydropower resources. The following sections of PURPA, in particular, apply to the development of hydroelectric power. a. TITLE 11. -This title requires utilities to purchase energy from small developers at rates that are "just and reasonable," but not at a rate that will exceed the utility's avoided costs of generating the energy. Section 210 specified that Title II applies to hydropower plants with an installed capacity of 80 MW or less. ASCE/EPRI Guides 1989 9-4 FERC may exempt small hydropower facilities (less than 30 MW) from the Federal Power Act, and from applicable state laws and regulations "if the Commission determines such exemption is necessary to encourage cogeneration and small power production." b. TITLE W.-Section 405 of this title requires FERC to establish a program of simpli- fied licensing procedures for small hydro at existing darns (up to 15 MW). Section 405, however, affirms the applicability of all relevant federal environmental legislation in con- nection with this title and requires FERC to consult with the Council of Environmental Quality and the EPA regarding the possible environmental effects from the construction of such projects. In response to Title IV, FERC has developed a short-form application for conduits and for existing site projects, especially for projects of 1.5 MW or less. 8. The Clean Water Act The stated objective of the Clean Water Act is to restore and maintain the chemical, physi- cal, and biological integrity of the waters of the United States. This act provides limits on the discharge of substances (including dredged or fill material) into waterways through a permit system. Applicants should consult with state water quality agencies regarding the applicability of this act. If the construction or operation of a project will affect a domestic water supply, the regional Environmental Protection Agency office should be consulted. Section 401 authorizes state water quality agencies or the EPA to issue Water Quality Certificates, which primarily address minimum strearnflows and pollutants. FERC requires each applicant to acquire such a certificate. Federal agencies must also consult with each state water quality department in which their project will be built. Water Quality Certificate standards may vary from state to state. Section 404 gives the Corps of Engineers the authority to issue permits regarding the dis- charge of dredged or fill materials into the waters of the United States. These materials must be disposed of at sites selected under EPA guidelines. FERC requires every applicant to obtain a Section 404 permit, unless it is not applicable. Federal agencies are exempted from this requirement, but have agreed to comply with Section 404 guidelines. 9. The Federal Power Act Section 811 of this act authorizes FERC to require fishways prescribed by Federal fishery agencies (see the Fish and Wildlife Coordination Act). Section 4(e) requires FERC to gain Corps of Engineers approval before issuing any permit to a project that would have an impact on a navigable waterway (see the Rivers and Harbors Act of 1899). 10. The Electric Consumers Protection Act (ECPA) of 1986 This legislation amends the Federal Power Act. Significant highlights of the ECP A include the following: Small hydro Clean water Section 401 Section 404 Navigation Competitive licensing 9-5 ASCE/EPRI Guides 1989 Recreation Historic preservation Trails • Creates a competitive process under which a new license will be awarded to the appli- cant with the proposal which best serves the public interest on the basis of nonpower as well as power values. • Fish and wildlife considerations are to be given "equitable treatment" with power issues. • Requires FERC to investigate license violations and gives FERC new authority to enforce license terms and provisions. o The conduit exemption in the case of water supply for municipal purposes is expanded. o Gives greater environmental protection and control over new dams and diversions receiving the benefits of classification as small power production facilities under PURPA. o Specifies the charges for using federal dams and other structures. 11. The Heritage Conservation Act of 1963 Public Law 88-29 ensures that adequate outdoor recreation resources are conserved and developed for public use. This act directs that developers take recreational uses into consid- eration when planning and constructing hydro projects. It is implemented by FERC and the Department of the Interior. 12. The Federal Water Projects Recreation Act of 1965 This act requires federal development agencies to consider the enhancement of outdoor recreation and fish and wildlife resources when planning water resource projects. 13. Historic Preservation Acts The National Historic Preservation Act of 1966 (Public Law 89-665) established a National Register of Historic Places. A project must be reviewed by the National Park Service and the State Historic Preservation Office to determine whether it will affect sites currently list- ed or considered for inclusion on the National Register. In some cases, older dams being considered for hydropower development are themselves listed on the register. The Archeological and Historic Preservation Act of 1974 (Public Law 93--291) is intended to preserve historic and archeological data that might be destroyed as a result of federal pro- jects or activities. FERC or state Historic Preservation Offices may request an inventory before project licensing or construction. 14. The National Trails System Act of 1968 Public Law 90--543 establishes a national system of recreational and scenic trails of historic significance. Existing trails, including the Appalachian Trail and the Pacific Crest Trail, are managed by the U.S. Forest Service and the Department of the Interior. Hydropower devel- opers must consult with FERC and the Departments of Agriculture and the Interior during planning of any hydropower project that may affect these existing trails. ASCE/EPRI Guides 1989 9--6 15. The Coastal Zone Management Act of 1972 Public Law 92-583 preserves, protects, develops, and restores the resources of the Nation's coastal areas. Federal funds are provided to help the states protect and manage their coastal lands. If a hydropower project is planned in an area subject to the jurisdiction of a coastal zone commission sanctioned under this act, the project is subject to the provisions of the commission's coastal zone plan. 16. Public and Indian Lands If a project or its reservoir will be wholly or partially located on Indian or public lands (to include lands controlled by state or federal agencies), the U.S. Forest Service, Bureau of Land Management, and Bureau of Indian Affairs should be consulted. 17. Navigation and Flood Control If a project will affect flood control operations or any navigable waterway of the United States, the applicant must consult with the appropriate district of the U.S. Army Corps of Engineers. The Corps will also comment on environmental impacts of the project. If hydropower development is considered as a Corps project, the agency must be consulted throughout the planning and design project. Additional discussions of the above legislation as well as references for the amendments to the legislation can be found in Division I, "Planning" of the Conventional Guidelines. D. CUMULATIVE IMPACTS The last area of environmental impact investigation examines cumulative effects of other projects that might make the impact of a new project either greater or less than the new project would be by itself. For example, the effect of only one reservoir and dam on the downstream passage of smolt on the Columbia River is quite small. However, the cumula- tive impact of all the dams has a significant effect on the numbers of young fish reaching the sea. Because widespread interest is relatively new and few cumulative impact assessments have been completed, there are no established procedures for this type of analysis. Early identifi- cation of the need to perform a cumulative impact assessment on a project is essential because these studies can consume large amounts of time and money. E. REFERENCE FERC (Federal Energy Regulatory Commission), "Application Procedures for Hydropower Licenses, License Amendments, Exemptions, and Preliminary Permits." FER C-O 1001, Washington, D.C., 1985. Coast Indians Navigation and floods Cumulative impacts 9-7 ASCE/EPRI Guides 1989 CHAPTER 10. PROJECT SCHEDULE CONTENTS Section Page A. Introduction ............................................................................................................................................... 1 0--1 B. Preliminary planning ................................................................................................................................. 1 0--1 C. Regulatory issues ...................................................................................................................................... 10--1 D.l)esign and construction ............................................................................................................................ l0--1 ASCFJEPRI Guides 1989 CHAPTERlO. PROJECTSCHEDULE A. INTRODUCTION Few generalities can be made to describe the scheduling of a small-scale hydroelectric pro- ject. As a project progresses, its perception and detail change and, as a result, the project schedule changes. Project schedules are best presented and understood from a timeline. Timeline Such a graphical presentation for all components facilitates planning and identification of critical scheduling. For small-scale hydro facilities, the scheduling can be divided into three components: (1) preliminary planning, (2) regulatory issues, and (3) design (including the preparation of bid documents) construction. B. PRELIMINARY PLANNING Issues that should be considered are described in Division I, Chapter 2, "Development of Level and Scope of Study Plan." The focus should be directed to decisionmaking based upon data collection and analysis. The feasibility report should indicate whether an invest-Data collection ment should be made to proceed with design and construction. It should also provide suffi-and analysis cient data for a license application to FERC. The data requirements for the license applica- tion and design are project dependent, and the project schedule should be based upon the collection and analysis of relevant data. C. REGULATORY ISSUES Regulatory issues primarily refer to FERC licensing requirements, described in Chapter 9, FERC "Institutional Issues." Licensing requirements have been in constant evolution over the last licensing decade, and the time requirements for licensing have constantly increased. Recognizing that most small-scale hydro facilities have been built in less than one year and seldom longer than two years, the regulatory issues may take from one to three years to resolve. Regulatory issues are often beyond the control of the design engineer, and ample time should be allowed. D. DESIGN AND CONSTRUCTION While regulatory issues are being solved, the design may be started depending on the issues Design considered by the regulators. Because regulatory issues influence the design of the project, design cannot be completed until after the license is issued. The design phase includes the preparation of bid documents. The bid documents should Construction include the instructions to bidders, bid sheets, general and special conditions, technical specifications, and bid drawings defining the project features. The project work may be divided into a separate equipment supply contract and a general civil works contract, or these may be combined into one contract for smaller projects. The separate equipment supply contract is usually more convenient for low-head, large- discharge units in the 8-to 15-MW size. The separate equipment supply contract may include the turbines, governors, generators, and excitation equipment. If a long water con- 10--1 ASCE/EPRI Guides 1989 ductor is involved, a separate supply contract for the penstock may be needed. This equip- ment must be delivered to the site with sufficient lead time to permit timely installation by the general civil worlc.s contractor. The rest of the equipment, including the transformer, switchgear, powerstation crane and general electrical and mechanical equipment, should be provided by the civil works contractor. The overall integrated schedule must consider the time required to design, fabricate, and deliver electro-mechanical equipment to the site. The bid period should include the time for the contractor to prepare the bid and for the owner to evaluate, negotiate, and award the contract. The total time usually ranges from 4 to 6 months for a small hydro project. After the award of the contract, the critical path of construction is affected most by: • Mobilization and construction of site access o Diversion and site dewatering o Opening material borrow and disposal areas o Excavation and foundation preparation o Concrete placement o Installation of electro-mechanical equipment • Testing and placing the unit in commercial operation The planning and scheduling of construction activities must consider the effect of climatic conditions at the site. This includes temperatures, length of freezing season, depth of freez- ing, rainfall, and river discharges and related flow depths. Diversion is normally accomplished in the low-flow season to avoid high river stages. Placement and compaction of fills is practically impossible during the rainy season, which may be extensive in some regions. Similarly, placement and compaction of fills may be difficult and have to be delayed during long freezing seasons. Scheduling the placement of concrete for larger units must consider the number of monoliths in which the powerhouse will be constructed and the number of lifts in each monolith. Each lift will usually require 8 to 10 days for stripping and resetting forms; installing reinforcement, embedded parts, pip- ing and electrical conduits; and placing concrete. The number of monoliths generally deter- mines the number of concrete crews that can work simultaneously. ASCEIEPRI Guides 1989 10-2 CHAPTER 11. COST ESTIMATES CONTENTS Section Page A. Introduction ............................................................................................................................................... 11-1 B. Screening tools .......................................................................................................................................... 11-1 C. Reliable cost estimates .............................................................................................................................. 11-1 D. References ................................................................................................................................................. 11-1 / ASCE/EPRI Guides 1989 CHAPTER 11. COST ESTIMATES A. INTRODUCTION Cost estimates are a critical feature of project planning and analysis. Cost estimates that are Importance too high can result in the elimination of worthwhile projects, whereas cost estimates that are too low can result in needless expenditures of money and resources on projects that are not economical. With cost estimates that are too low, one may proceed to the bidding stage before canceling an uneconomical project and opening the engineer to criticism. Thus, the importance of accuracy in estimating costs is critical, and estimates should be performed carefully. B. SCREENING TOOLS A series of cost cutves have been developed to setve as initial screening tools. The first of Cost curves these cutves was reported by the Corps of Engineers [COE, 1979] and later expanded by the Bureau of Reclamation and EPRI [1980]. These cutves are indexed as of July 1978 to the Bureau of Reclamation cost indices as reported quarterly in Engineering News-Record. Screening equations have been described in other recent articles. The value of the screening cUIVes is to identify sites with the best opportunities for hydroelectric development When cost estimation aids are improperly used, significant errors can occur. Based on an EPRI/OOE study [ 1985], Christensen [ 1986] reported that "cost graphs for turbines, gener- ators, electrical equipment, hydraulic gates, and valves can be used with reasonable confi- dence as long as they are updated regularly" and that "the cost of civil works for intake structures, darns, spillways, and powerhouses cannot be reliably estimated by general cost graphs unless careful consideration is given to specific site conditions." C. RELIABLE COST ESTIMATES Because of the importance of cost estimates in the evaluation of small-scale hydro facili- ties, it is strongly recommended for the civil works that quantities and materials be deter- mined from a site-specific layout and that a detailed cost estimate be developed from this site-specific data. Help can be obtained from numerous sources, such as experienced con- tractors or equipment suppliers. The EPRIIDOE study in volumes 1, 2, and 4 [EPRI!DOE, 1985] reported on the problem in hydropower development from lessons learned in the DOE demonstration program -including the problems in cost estimating. A good summa- ry by the project manager on problems and procedures for cost estimating appears in a two- article series in Hydro Review [Christensen, 1986]. The importance of a detailed, site-spe- cific cost estimate cannot be overemphasized. D. REFERENCES Christensen, J.P., "Cost Estimates: What a Hydro Developer Needs to Know," Hydro Review, Spring 1986. EPRI/DOE, "Small Hydropower Development: The Process, Pitfalls, and Experience," 1985. Reliable cost estimates 11-1 ASCE/EPRI Guides 1989 EPRI, Simplified Methodology for Economical Screening of Potential Low-Head, Small-Capacity Hydro Sites, Tudor Engineering, 1980. COE, Feasibility Studies for Small-Scale Hydropower Additions-A Guide Manual, July 1979. ASCE/EPRI Guides 1989 11-2 CHAPTER 12. ECONOMIC ANALYSIS CONTENTS Section Page A. Introduction ............................................................................................................................................... 12-1 B.Costs .......................................................................................................................................................... 12-1 C. Benefits ..................................................................................................................................................... 12-1 D. Economic assesSillent ................................................................................................................................ 12-2 1. Benefit-cost ratio method ...................................................................................................................... 12-2 2. Internal rate of return method ............................................................................................................... 12-2 3. Computer models .................................................................................................................................. 12-2 E. Optimizing plant size using approximate economic methods ................................................................... 12-3 ASCFJEPRI Guides 1989 CHAPTER 12. ECONOMIC ANALYSIS A. INTRODUCTION The economic analysis of a small-scale hydropower facility compares project costs with the Costs vs. benefit derived from the sale of the energy. From this comparison, project return on invest-benefits ment is computed. B. COSTS Project costs include the types listed below: • Construction costs. Construction costs include all direct and indirect costs related to Types of costs the design and construction of the facility. • Costs of interest during construction. Interest accrued during the construction peri- od should be computed at the prevailing interest rate for borrowed funds. For small hydro projects, the construction period is usually between 18 and 30 months, depend- ing on size and complexity. • Project capital costs. Addition of the accrued interest to the total construction cost gives the project capital cost. • Recurring annual costs. Recurring costs include the average annual costs for opera- tion, maintenance, replacement, insurance, and general expense. Where applicable, the cost of obtaining water rights, or falling water rights (headwater benefits), should be included if paid annually. • Tax costs. Applicable taxes should be included in any economic evaluation. Such taxes for a small-scale hydro facility include: • Income tax (federal, state, and local) • Ad valorem tax or property tax • Franchise tax • Capital stock tax • Gross earnings or receipts tax • Other local fees or taxes • Total annual costs. The total annual cost of the project can be estimated as the sum of the above recurring costs and taxes together with the annual costs of amortization based on the assumed project life and interest on the capital cost. An interest rate appropriate to the current financial and investment climate should be selected. C. BENEFITS Project benefits commonly derive from the sale of energy at a negotiated contract price or "avoided cost" PURPA rate, to a utility. Nonnally, there is a differential and higher benefit paid for energy delivered during the system's peak usage period. Therefore, if possible, the project operation should be established to maximize this differential benefit In conducting the economic analysis, it is common practice for a small-scale hydro facility SO-year life to be considered as having a 50-year life. However, where existing civil works facilities are 12-1 ASCE/EPRI Guides 1989 Constant dollars Escalating dollars used, their physical condition may require a judgmental decision to consider a shorter peri- od of analysis. Another factor that could affect the period of analysis is a valid FERC license on existing facilities that expires before the end of the estimated life of the pro- posed project. D. ECONOMIC ASSESSMENT 1. Benefit-Cost Ratio Method One approximate method of economic assessment is the benefit-cost ratio. This analysis can be conducted using constant dollars or escalating dollars. When assuming constant dollars, the costs and benefits derived are based on values pre- vailing at the date of the study. Where the ratio is greater than 1.0, the project can be con- sidered economically feasible. An alternative approach is to use the constant dollar values for everything except the energy costs, which can be escalated at appropriate rates per annum. This analysis is intended to reflect the real change in value of energy with respect to other costs. If desired or where the benefit-cost ratio obtained by the constant dollar approach is less than l.O, an analysis can be made to account for future price escalation. Items subject to such variation are the costs of operation and maintenance, general expenses, insurance, taxes, and the values of energy. The values associated with the project capital cost and the dependable capacity should not be affected by inflation when these represent alternative fixed expenditures that would have been made during the construction of the hydro plant. In summary, the benefit-cost ratio method using either the constant or escalating dollar approach is based on a comparison of benefits to costs over the anticipated life of the pro- ject. Where this ratio is greater than 1.0, the project is normally considered to be economi- cally feasible. This method does not define rates of return for the investment. 2. Internal Rate of Return Method For some users it may be preferable to obtain an internal rate of return instead of selecting an interest rate for the economic analysis. In this case, the benefit-cost ratios would first be computed for a series of interest (discount) rates. The interest rate that gives a benefit-cost ratio of 1.0 is then found from a simple plot of discount rates against internal rate of return. It can be evaluated within the user's policy for making fmancial expenditures to determine the economic suitability of the plant, or it can be used in ranking alternative projects. 3. Computer Models Most entities involved in the development of small-scale hydro facilities now have com- puter models that analyze project economics by computing cost and benefit streams and then use these results to compute the rate of return for various investment scenarios. The advantage of these models is that many alternative plant configurations can be analyzed quickly, and the economic model can be used to optimize both plant sizing and rate of return simultaneously. ASCE/EPRI Guides 1989 12-2 E. OPTIMIZING PLANT SIZE USING APPROXIMATE ECONOMIC METHODS If it is desired to optimize the plant capacity using approximate economic methods, outputs can be obtained for each of the ranges of plant capacities selected. Annual costs and bene- fits are then determined for each capacity. The preferred plant capacity can be selected as that at which the incremental cost equals the incremental benefit. A simple graphical procedure that can be used to obtain this capacity is described in the steps below: 1. Plot a graph of plant annual cost against plant capacity. 2. On the same grid, also plot a graph of plant annual cost against annual benefits, using the same scale for each axis. 3. Draw a line at 45°(1:1) to either axis and tangent to the benefit-cost curve; the tan- gent point will define the preferred capacity at which incremental benefit equals incremental cost. 4. Project this point to the cost-capacity curve to obtain the value of the optimum plant capacity, this value may be rounded to an even number as appropriate. Either the constant dollar or escalated value approach can be used, but the optimum capaci- ties selected will differ somewhat in value according to the approach used. Following selection of the plant capacity, the power-cost-benefit procedures can be repeat- ed for that capacity or, alternatively, the values can be obtained by graphical interpolation of the data obtained previously for the selected range of capacities. Where the internal rate of return approach is preferred, it will nevertheless be simpler to carry out the plant sizing procedure on the basis of one selected interest rage, then to deter- mine the internal rate of return for the adopted capacity. Graphical procedure 12-3 ASCEIEPRI Guides 1989 SMALL-SCALE HYDRO DIVISION II. DESIGN Chapter 1. Storage, Diversion, and Appurtenant Structures Chapter 2. Waterways Chapter 3. Power Plants Chapter 4. Substation and Transmission Lines ASCE/EPRI Guides 1989 Section CHAPTER 1. STORAGE, DIVERSION, AND APPURTENANT STRUCTURES CONTENTS Page A.I>efinition and type ...................................................................................................................................... 1-1 B. Field data requirements ............................................................................................................................... 1-2 1. Topographic maps ................................................................................................................................... 1-2 2. Geologic maps ........................................................................................................................................ 1-2 3. Hydrologic infonnation .......................................................................................................................... 1-2 C.I>esign of storage and diversion structures ................................................................................................. 1-3 1. Type, size, and arrangement ................................................................................................................... 1-3 2. Hydraulic and structural design .............................................................................................................. 1-4 a. Barrages and weirs ............................................................................................................................. 1-4 D. Material specifications .............................................................................................................................. 1-11 E. Spillways ................................................................................................................................................... 1-12 F. Low-level outlets ....................................................................................................................................... 1-20 G. Sediment control ....................................................................................................................................... 1-21 H. River diversion during construction .......................................................................................................... 1-25 I. References ................................................................................................................................................. 1-26 FIGURES Figure 1-1 Typical powerhouse arrangements .......................................................................................................... 1-5 1-2 Diversion darn used to divert water into a forebay ................................................................................. 1-6 1-3 Diversion darn used to divert water into a power canal .......................................................................... 1-7 1-4 Diversion of water into a conduit ........................................................................................................... 1-8 1-5 l'ypical flashboard configurations .......................................................................................................... 1-9 1-6 Section of gabion darn .......................................................................................................................... 1-10 1-7 Plan of typical emergency spillway ...................................................................................................... 1-13 1-8 Typical layout of side-channel spillways .............................................................................................. 1-14 1-9 Siphon spillway-typical sections ...................................................................................................... 1-15 1-10 'fypical riprap protection ....................................................................................................................... 1-16 1-11 'fypical gabion walls ............................................................................................................................. 1-17 1-12 Labyrinth spillway ................................................................................................................................ 1-18 1-13 Semicircular spillway ........................................................................................................................... 1-19 1-14 Spill ways with double-sided crests ....................................................................................................... 1-19 1-15 Sections of a typical outlet structure ..................................................................................................... 1-20 1-16 Submerged vanes .................................................................................................................................. 1-23 1-17 Concave/convex guide bank: ................................................................................................................. 1-23 1-18 Extended groyne wall ........................................................................................................................... l-23 1-19 Cantilever platfonn ............................................................................................................................... 1-23 1-20 I>esiltation basin ................................................................................................................................... 1-23 1-21 Silt excluder .......................................................................................................................................... 1-24 1-22 Silt extractor, or ejector ......................................................................................................................... l-25 1-23 Haystack, or straw bale, darns .............................................................................................................. 1-26 ASCE/EPRI GUIDES 1989 CREDITS The "Storage, Diversion, and Appurtenant Structures" chapter was written by: Anand Prakash, Ph.D., P.E. Chief Water Resources Engineer Dames and Moore 1626 Cole Boulevard Golden, Colorado 80401 ASCEIEPRI GUIDES 1989 CHAPTER 1. STORAGE, DIVERSION, AND APPURTENANT STRUCTURES A. DEFINITION AND TYPE Economic considerations usually dictate that small hydroplants are installed at existing dams. Where a new dam must be constructed as part of a small-scale hydropower project, detailed investigations and analyses are required to develop a safe and economical design for the dam. Guidelines and methods for conducting such investigations and analyses and for designing different types of dams are given in Design of Small Dams [USBR, 1987], Design of Gravity Dams [USBR, 1976], Design of Arch Dams [USBR, 1977], Handbook of Dam Engineering [Golze, 1977], Engineering for Dams [Creager et al., 1945], and Earth and Earth-Rock Dams [Sherard et al., 1963]. In addition to the abovementioned investigations, analyses, and designs, the construction of a new dam usually requires an environmental impact statement (EIS) or environmental report and a number of permits from local, state, and federal agencies [Golze, 1977: ch. 1; USBR, 1987: ch. 2]. Most of the dams described in the Conventional Hydro Guidelines, are suitable for small hydroelectric installations. In addition to the dams required for the development of conventional hydropower, certain relatively small storage and diversion dams (weirs) may also be suitable for small hydropower development. These include: • Rock.fill or concrete weirs with or without flashboards provided as diversion and stor- age structures across stream channels • Barrages (gate-controlled) provided as diversion and storage structures across existing waterways • Timber or steel cribs filled with rock and with steel or concrete facing to minimize seepage • Steel frames with skin plates joined together to hold water, supported by steel props or frames on the downstream side • Timber dams with wooden planks joined together to hold water, supported by wooden or steel props on the downstream side • Dams formed of gabions with steel, concrete, or synthetic liner on the upstream face • Inflatable rubber or synthetic fabric dams • Cofferdams with or without impervious membranes on their upstream faces • Dams constructed with fabriforms or fabricast bags filled with fme-aggregate concrete • Rockf'ill with upstream concrete facing • Rollcrete (roller-compacted concrete, or RCC) Diversion dams 1-1 ASCE/EPRI Guides 1989 Maps Geologic information Hydrologic data B. FIELD DATA REQUIREMENTS 1. Topographic Maps For hydrologic analyses pertinent to hydroelectric development on an existing or proposed dam site, the 71/2 minute (1 in= 2,000 ft) quadrangle maps of the U.S. Geological Survey with a contour interval of 20 feet provide sufficient information about the drainage area. Additional detailed survey maps are required to estimate available storage, height of dam, and available head, and to locate various structural elements of the dam and power plant These supplementary maps should preferably be on a scale of 1 inch = 100 feet, with a contour interval of 2 feet. More detailed maps may be required for small impoundments on relatively flat terrains, whereas larger scales and contour intervals may be adequate for larger impoundments in steep valleys. For small hydropower development on existing dams, construction drawings of the dam and its appurtenances should provide adequate information for locating the powerhouse and other structural components. 2. Geologic Maps Geologic maps of the damsite area or vicinity are usually available from the state or U.S. Geological Survey (USGS). 'These maps should be reviewed to ascertain whether there are adverse geologic conditions requiring expensive foundation treatment for the construction of the dam or powerhouse at the selected location. This information should be supplement- ed by one or more borings at the locations of the dam and powerhouse. Soil maps of the watershed should be obtained from the U.S. Soil Conservation Service (SCS), Bureau of Land Management (BLM), U.S. Forest Service (USFS), or other local agencies. This information is used to estimate the hydrologic characteristics of the water- shed upstream of the damsite. Additional information on geotechnical investigations for small hydroelectric installations is given in [EPRI, 1981; COE, 1979b; COE, 1985; and USBR, 1980a]. 3. Hydrologic Information Hydrologic information required to design a small-scale hydropower plant is generally the same as that for a conventional hydroplant: • Hydrologic characteristics of the drainage area • Flow frequency curve • Probable maximum flood (PMF) • Hazard potential • Develop spillway design flood hydrograph • Design-basis floods and flood protection requirements for all components of the power plant • Diversion design flood • Daily and monthly streamflow data for a period of 20 years if available ASCE/EPRI Guides 1989 1-2 o Daily and monthly flow-duration curves o Mass curve of daily and monthly flows o Elevation-area-storage curve for the impoundment o Spillway and outlet rating curves o Downstream water-release requirements • Downstream discharge versus tail water elevation curve • Estimated rate of reservoir sedimentation o Monthly lake evaporation rates • Seepage losses, water requirements for fish bypass, and other direct diversions from reservoir storage upstream of the power plant • Operational constraints on single or multipurpose use of storage Additional information on hydrologic investigations for small hydroelectric installations is given in the publications mentioned previously [EPRI, 1981; COE, 1979b; COE, 1985; and USBR, 1980a]. C. DESIGN OF STORAGE AND DIVERSION STRUCTURES 1. Type, Size, and Arrangement If the type of storage or diversion structure selected is a conventional earth or rockfill, con- crete gravity, concrete arch or buttress, or roller-compacted concrete dam, then the size and arrangemem of structures should be determined by the methods described for conventional hydropower plants. The same methods are used when the power plant is to be retrofitted into an existing dam by providing a power conduit through the dam. The other type of storage and diversion structures that may be used for small hydropower development are listed in Section A. The methods used to determine the storage capacities, spillway sizes, and heights of these dams are the same as those for any conventional water supply dam. These methods are well documented in the literature [Davis and Sorensen, 1970: ch. 4; Linsley and Franzini, 1972: ch. 7; Golze, 1977: chs. 1 and 2; USBR, 1987: ch. 1; and Creageret al., 1945: ch. 5]. They include: o Developing and using the mass curves of available streamflows and anticipated demands of the proposed project to estimate the capacity of the required storage and diversion structure. • Estimating the power generation potential at the site with different sizes and capaci- ties of the proposed storage and diversion structures and the time-variant nature of available streamflows using computer programs like the HEC-3 and HEC-5 [COE, 1974 and 1979a]. • Estimating the hazard potential and design basis flood for the spillway and flood rout- ing computations to select the least expensive combination of dam height and spill- way size using computer programs like the HEC-1 [COE, 1987], TR-20 [SCS, 1969], and TR-55 [SCS, 1975]. Typical arrangements of power plants that use a conduit through an existing or proposed conventional dam are shown on figure 1-1. The general arrangements of small hydropower plants using some of the diversion dams listed in section A are shown on figures 1-2, 1-3, Reservoir sizing 1-3 ASCE/EPRI Guides 1989 Hydraulic analysis and 1-4. On figure 1-2, the diversion dam is used to divert water into the forebay of a powerhouse; on figure 1-3, water is diverted into a power channel, and the powerhouse is located at the tail end of the power channel; and on figure 1-4, water is diverted into a con- duit that will become the penstock of a proposed powerhouse. 2. Hydraulic and Structural Design The designs of earth and rockfill, concrete gravity, concrete arch or buttress, and roller- compacted concrete dams are described in the chapter on dams in the conventional hydro volume. Design criteria for the other types of dams listed in section A are described in the following paragraphs. a. Barrages and Weirs. - A barrage is a diversion structure constructed across natural or man-made waterways. It has a concrete or masonry weir in its bottom portion and a system of gates in its top portion. The ponding of water is accomplished primarily by means of gates. The power plant may be located in one of the bays of the barrage. Alternatively, water may be diverted to the power plant through a conduit or power channel. The design of barrages constructed on rigid bed channels is similar to the designs of drop structures, low-head weirs and spillways, and energy dissipation devices as documented in [USBR, 1987: chs. 9 and 10; USBR, 1978a: ch. 2; USBR, 1978b; COE, 1959; SCS, 1973; and SCS, 1976a]. In principle, this involves the following: • Hydrologic and hydraulic analyses to determine the length, crest elevation, and shape of the weir crest necessary to pass the design flood. For preliminary esti- mates of the crest width and gate height, this may include use of the weir and orifice flow equations to pass the peak design discharge. The coefficients of discharge may be taken from [USBR, 1987: ch. 9; and Davis and Sorensen, 1970: ch. 2]. For detailed designs, flood routing computations should be performed using computer programs like the HEC-1 [COE, 1987], TR-20 [SCS, 1969], and TR-55 [SCS, 1975] to finalize the crest width and gate height. • Hydraulic analyses to develop alternative combinations of weir heights and gate sizes to impound the desired quantity of water without undue flooding in the upstream reaches due to back water. This may include backwater computations using computer programs like HEC-2 [COE, 1982], and WSP2 [SCS, 1976b] or hand computations using the open-channel flow equations for gradually varied flow [Chow, 1959: ch. 10]. • Hydraulic analyses to determine the characteristics of the hydraulic jump down- stream of the weir crest under different discharge conditions, length of the downstream apron, depth of expected scour, and extent of the required down- stream erosion protection. [Chow, 1959: ch. 15; Davis and Sorensen, 1970: ch. 17]. • Economic analyses to optimize the weir width and height, gate size, apron sizes and slopes or approaches on the upstream and downstream sides of the weir crest, and the design of energy dissipation arrangements. This includes estimation of preliminary costs of the alternatives developed using the aforementioned hydrolog- ic and hydraulic analyses. ASCE/EPRI Guides 1989 1-4 CANAl. OR DAM WI NEW PEHSTOCIC CONCRETE DAM WIEXISTING CONDUrT ' ====. I . I EARnt DAM W/EXISTING OUTUT WORKS Figure 1-1.-Typical powerhouse arrangements. 1-5 ASCE/EPRI Guides 1989 Subsurface considerations Flash boards RIV{h I GUI(Jf tiA NIC CUIOI. IJIINI( {)IVIOt WAlL -----/ ~ ~---'l-:-~..-~-~..-:·_,::..-.~'.....,:..-s-uf "~"":··~w·E-, ..... ~-./~1 -,r.-=:::::r~_c_ Figure 1-2.-Diversion dam used to divert water into a forebay. The methods of designing barrages on penneable foundations are described in [Davis and Sorensen, 1970: ch. 17; Harr, 1962: ch. 5; Khosla et al., 1962; and Leliavsky, 1965]. The designs of these structures require both surface and subsurface flow considerations. 1be surface considerations include the hydrologic and hydraulic analyses described previously. The subsurface considerations include the following: • Estimation of the maximum uplift pressures below the floors of these structures and provision for adequate structural safeguards [Prakash et al., 1978; Khosla et al., 1962; Davis and Sorensen, 1970: ch. 17]. • Estimation of the maximum exit gradient at the downstream end of the floors of these structures and provision for adequate safeguards [Khosla et al., 1962; Prakash et al., 1978; Davis and Sorensen, 1970: ch. 17]. • Estimation of the maximum scour depth at the toe of the structure given the particle size distribution of the bed material and provision for adequate safeguards [Davis and Sorensen, 1970: ch. 17]. The hydraulic design considerations for the timber or steel cribs, steel dams with skin plates, and timber dams with wooden plates are the same as those for the barrages. Rockfill weirs with or without flashboards have been used to impound water since the 19th century. A few typical flashboard configurations and designs are shown on figures 1-5. The gabion dam is an improved version of the same concept. Gabions may be used with and without flashboards to impound water for small hydroelectric installations. ASCEIEPRI Guides 1989 1-6 Rock apron F'iow Block aoron Impermeable Hoor 1 I We1r I . 1 sect1on 1 ' Pervious block ocr on Baffle block 1 • '\. Rock apron Pile line "A"~ I !--Intermediate ~ p1le line v-Filter Impermeable floor Pile line .. 8 .. ~ Exit gradient I I I \ \ \ \ \ \ \ \ ~.. __ ~-Flood protection bund \ ' ~oin bund '-a reaching section PERMEABLE FOUNDATION Section through ba.rr:::s.ge Flood---~ protection bund Under Sluices\ /Regu lot or Moen bund~ .~ CANAL Borroqe Jl=====~r--Guide bonk ~ ~ ,."' I ' ' ,. I ', \ Figure 1-3.-Diversion dam used to divert water into a power canal. [Davis and Sorensen, 1970: ch. 17]. Canol'\.. 1-7 ASCE/EPRI Guides 1989 \ POSSIBlE r __. / -); FUlllAE PU4STOCI ' / / / / ~ ~ ~J[[~ ·, / -~- [ =-__ -=r .. ·~_/', (') / ~.:· ·.· , • 4i 42' HOW[U-BUNCER------r 0 __ "\_~,----·<-VllV[ ~~ -'-:.::_-_:: .--:= -\ 18' H0WEll·BUNCER ""'"" ' ~J ' "" ._::_; --·~.;--:,t~tt-,----" \~~ ----- SECTION H 5 15 ~- 0 10 JO ,----OPEIIl T OR SCll£ 114 HE T SECTION ALONG CUHERLINE OF OUTLET WORKS Figure 1-4.-Diversion of water into a conduit. [Mascolo, 1987]. 45 1 The design principles of gabion and riprap dams are described in brochures published by gabion manufactures [Terra Aqua, 1983; and SCS, 1976a], respectively. Additional infor- mation on design criteria for the use of gabions is available in [Simons et al., 1984]. The life of gabions may be as long as 50 years or more with the use of galvanized or synthetic wires. The section of a typical gabion dam is shown on figure 1-6. The basic principles for stability analyses of low-head dams are the same as for large dams. The forces to be estimated for stability analyses of these dams include: 1. Horizontal water pressure 2. Weight of the dam and its appurtenant works 3. Uplift pressures 4. Silt loads and ice pressure 5. Dynamic pressures caused by earthquakes 6. Extra loads anticipated during dredging and maintenance These forces are discussed below. ASCE/EPRI Guides 1989 1-8 :b f;; ~ '2 Cl c ~ en -\0 00 \0 2"xl2"•8'-0" PLANKS -v '""·'-· _\·1 l > ... "'•'-'• J ~i - --1/.2 3/8"1> 0 PIN--~ • -"' 1-t \ -- ~ tlh ~) .... .:i ~ IIU :ll~ II~ SPILLWAY :1 -' 1!]1 CREST i!ll di__:... J" STD. PIPii: SOCKET _... DOWNSTREAM ELEVATION -- 2"'x4 .. CLEAT SECTION . . ' .. ;, .·: ·"': ..,. j (a) FLASHBOARDS W/PINS ~ . i - - - ll:•l •"'I :illt I 0 I "' I /5" 7 ( SPLASH PLATE H BEAMS'\. II II \\ ~~~!4--6"• U·BOLT-""-' PIPII HlliGE ) DOWNSTREAM ELEVATION -:-~j .. ·~:~·:'·-: SECTION (b) HINGED FLASHBOARDS ... '-_\..!, \.... • ..>1 oWl I Zl -.CI .., .. If II l1 2"x4" I fcL£ATs~ II II ~I I II d SPILLWAY CIIEST UPSTREAM ELEVATION 4"+ PIPE I 3'-0"oc 1 o•-o-oc PIN SECTION (c) FLASHBOARDS W/PROPS Figure 1-S.-Typical flashboard configurations. Courtesy Dames and Moore, 1984. us 7 Water Ltvel ___ , <~:=::::;:;::::::.-::::====:.'!.;,• fer Love I Horizontal forces Uplift pressures Caunrtr Dam Gabian eaus Figure 1-6.-Section of gabion dam. [Paudial et al., 1987]. Configuration selected should fit site and now conditions. Orcqtnal Canal Btd 1. Horizontal water pressure including dynamic loads due to water overflowing the dam and tailwater. The horizontal hydrostatic and hydrodynamic forces on darns may be evaluated as follows: where: w h ht c a y Hydrostatic force on the upstream face = O.S wh2 Hydrostatic force on the downstream face due to tail water= O.S wh 12 Hydrodynamic force due to earthquakes = 0. 726 Cawhy = = = = = = unit weight of water, depth of water above base, depth of tail water above base, dimensionless coefficient [Davis and Sorensen, 1970: ch. 9], earthquake intensity as a coefficient of the gravitational acceleration, and distance below reservoir surface where the hydrodynamic force is to be calculated. 2. Weight of the dam and its appurtenant works (e.g., gates and flashboards). This includes all vertical loads on the foundation of the darn. • Vertical load due to the mass of the darn • Vertical load due to water above the slopes of the darn • Vertical load due to silt deposit above the slopes of the dam 3. Uplift pressures on the foundation of the dam. For gravity darns, the uplift pres- sure on the foundation is assumed to vary from the full reservoir head at the heel to a ASCE/EPRI Guides 1989 1-10 fraction (usually taken to be 1/3 to 1/4) of the difference in head between reservoir and tail water along the line of the drains; thereafter, the uplift is assumed to follow a straight-line drop to the tailwater elevation at the downstream toe. Methods to com- pute uplift pressures through permeable foundations are given in [Davis and Sorensen, 1970: ch. 17; Harr, 1962; and Khosla et al., 1962]. 4. Pressures from silt loads and ice. The horizontal force from silt deposited upstream of a dam (/3 ) may be estimated by the Rankine formula, where: w 3 h;(I-sin¢) fs = 2(1 +sin¢) w s = submerged unit weight of silt, h3 = depth of silt above foundation, and ¢ = angle of internal friction. (1-1) Ice pressures on dams are usually estimated empirically. For the continental United States, ice thrusts ranging from 5,000 to 20,000 lb/ft may be used depending on location. 5. Dynamic pressures caused by earthquakes. The dynamic pressures caused by earthquakes may act in any direction. Horizontal forces are produced by the inertia of the dam and vertical forces are caused by the upward component of the seismic acceleration. These forces are calculated by using the earthquake coefficient applica- ble to the seismic zone where the dam is located. The maps of the seismic zones along with the coefficients of earthquake acceleration and factors of safety used for designs of dams are given in [COE, 1976; and NAP, 1985: chs. 6 and 10, app. B]. Forces on submerged structures have positive pressures on the upstream side and neg- ative pressures on the downstream side caused by movement of the structure or fluid. 6. Extra loads anticipated during dredging and maintenance of the reservoir. These loads can be estimated using a modified height of the dam measured from the dredged bottom of the reservoir with a safety factor of 1.5 to 2 to account for impact loads from moving equipment. D. MATERIAL SPECIFICATIONS The specifications for the construction materials used for small hydropower plants and their appurtenant structures are generally the same as those for conventional hydropower plants. However, materials like timber or steel used for cribs, props, skin plates, planking, gabions, and synthetic liners may not be applicable to conventional hydropower plants. The specifications for structural steel and timber are given in the appropriate American Society for Testing and Materials (ASTM) standards. Specifications for rock and gabions may be adapted from those given in [DOT, 1970 and 1975] manufacturers' publications, e.g., S.P.A. Officine Maccaferri, Bologna, Italy and Terra Aqua Inc. Specifications for syn- thetic liners may also be obtained from manufacturers. Silt loads Earthquake forces Extra loads Construction materials 1-11 ASCE/EPRI Guides 1989 Earthcut spillway Side-channel spillway Morning Glory spillway E. SPILLWAYS The types and designs of spillways required for small hydroelectric power plants are the same as for conventional hydroplants. However, most dams suitable for small hydroelectric installations are small in height and storage capacity. Therefore, the spillways required for these dams are smaller in size and may be designed to pass the 100-year flood, one-half the probable maximum flood (PMF), or the entire PMF depending upon the size and hazard classification of the dam. The methods to determine the size and hazard classifications of dams and spillway design floods are described in [COE, 1976] and in Safety of Dams [NAP, 1985]. Where the spillway is designed to pass a flood lower than the PMF, special flood protection arrangements should be provided to protect the power plant and other pub- lic or private property against inundation in the event of overtopping or failure of the dam. Such flood protection measures may include one or more of the structures described in the following paragraphs. 1. An earth cut emergency spillway in the dam with riprap, grass, or asphaltic pro- tection against erosional damage. These spillways are excavated in a portion of the dam embankment and may be provided with earthen or armored approach and exit channels. Hydraulic design considerations for these spillways are given in [SCS, 1968; SCS, 1973; and Barfield, Warner, and Haan, 1981: ch. 4]. The plan of a typical emergency spillway is shown on figure 1-7. Potential lateral erosion may be con- trolled by installing sheet piling on sides, delineating the spillway. The riprap design criteria for the approach and exit channels are described in [Barfield, Warner, and Haan, 1981: ch. 3; Simons and Senturk., 1977: ch. 7; SCS, 1976a; COE, 1977; and COE, 1970]. 2. An uncontrolled concrete side-channel spillway provided on a side of the dam. 'These spillways may be used on sites where the sides of the valley are steep and the topography permits the construction of a spillway crest on a side of the reservoir with an exit channel parallel to the spillway crest The hydraulic design principles for these spillways are described in [USBR, 1987; Davis and Sorensen, 1970: ch. 20; and Chow, 1959: ch. 12]. Typical layouts of side-channel spillways are shown on figure 1-8. 3. An uncontrolled concrete or masonry weir provided across a stream as a portion of a barrage. These weirs are constructed as low diversion dams across stream chan- nels. A portion of the weir is provided with a lower crest (2 to 5 ft lower than the remaining and uncontrolled portion) and gates to maintain a deep pond of water on one side of the stream. The offtake channel or pipe is located on this side of the stream. Excess water is discharged over the uncontrolled weir. The gates in the undersluices (portion of weir with depressed crest) may be operated to pass extreme floods and to flush sediment deposited in the pond upstream of the offtake channel or pipe. The design principles of such structures are described in [Khosla et al., 1962; and Davis and Sorensen, 1970: ch. 17]. 4. An uncontrolled morning glory spillway or a battery of uncontrolled siphon spillways provided to pass excess flood inflows. These spillways are suitable to sites where space for providing the other types of spillways is limited. The design ASCE/EPRI Guides 1989 1-12 TOP OF SEDIMENT STORAGE Figure 1-7.-Plan of a typical emergency spillway. [Barfield et al., 1981]. principles for these spillways are described in [USBR, 1987: ch. 9; and Davis and Sorensen, 1970: ch. 20]. Additional infonnation for small siphon spillways is given in [USBR, 1978a: ch. 4]. Typical sections of a siphon spillway are shown on figure 1-9. The design details of the morning glory spillway are given in the chapter on spillways in the conventional hydro volume. 5. A fuse-plug spillway designed to fail when the water surface elevation in the reservoir reaches a prescribed maximum [USBR, 1987: ch. 9]. The fuse-plug spillway consists of a section of an eanh dam that is generally lower than the crest of the main dam. When overtopped this section is designed to fail by rapid erosion as it is overtopped so as to pass excess flood water without damaging the main dam. The designs of such sections are based on judgment, experience, and appropriate Fuse-plug spillway 1-13 ASCE/EPRI Guides 1989 Flood protection Labyrinth, semicircular, or double- sided entry hydraulic and geotechnical analyses to ensure that the intended failure would occur in the same way envisioned in the design [USBR, 1984]. In all cases, tailwater conditions resulting from high spillway discharges should be ana- lyzed to determine the potential for inundation of the power plant. Methods for these analy- ses include the HEC-2 computer program [COE, 1982], the DWOPER program [NWS, 1982], and the WSP2 program [SCS, 1976b]. If it is found that the tailwater elevations may inundate the powerhouse building, its ancil- lary structures, or access, then the affected facility may have to be protected by a flood wall, divide wall, or by a watertight dike or concrete box structure. These walls or dikes may be riprap-protected earth or rockfill structures, gabion structures, or concrete or masonry retaining walls. Typical riprap and gabion protections are illustrated on figures 1-10 and 1-11. The riprap size should be obtained from some suitable guide. It is related to the velocity associated with the discharge, slope, and flow acceleration. In many small hydropower installations, the space available for locating a spillway of ade- quate size may be limited due to topographic constraints or due to interference caused by some structural elements of an existing facility. In these cases, labyrinth, semicircular, or double-sided-entry spillways should be considered to obtain higher discharges per unit width of the spillway openings [Hay and Taylor, 1970; Prakash, 1987; and Cassidy et al., 1985]. The plans of labyrinth and semicircular spillways are illustrated on figures 1-12, 1-13 and 1-14, respectively. Ground Une on C.L GENERAL PLAN AND PROFILE Elev B End of Weir~ of Spillway Channel OF SIDE CHANNEL SPILLWAY 2919.00 W.S. Q= 30000c.f.s.l :N Control Scale of Feet Section 100 o 100 200 JOO Top of Concrete Uning El Rock Une 26~00 81 +I Elev.2864.60 ~~ Elev.2964.30 ~1 Q=30000c.f.s. !: Profile Cii L =420ft .; " = 0. 75, a = 0.25 Cii Figure 1-8.-Typical layout of side-channel spillways. [Creager et al., 1945]. ASCE/EPRI Guides 1989 1-14 Outlet transition Original ground surfac~ - SECTION A-A NWS Metal pan DETAIL A PROFILE L 3131 ~ Embedded I" i 1 a" Anchor bolts at 12" max., welded to L DETAIL 8 Figure 1-9. -Siphon spillway-typical section. [USBR, 1978a]. The principles and methodology for the design of stilling basins and energy dissipators for these spillways are the same as described in the spillways chapter in the conventional hydro volume. For smaller pipe or conduit spillways, impact basins may be adequate. The criteria for the design of these impact basins are described in [SCS, 1971; USBR, 1978a: ch. 6; and USBR, 1978b: sec. 6]. Nonnally, spillways provided on small hydroelectric installations are uncontrolled, and gates and hoists are not required. They are similar to those described in the spillways chap- ter in the conventional hydro volume. For small gates, simpler lifting arrangements, e.g., winches, counterweight, hand crank or wheel, and hydraulic controls may be considered. For stop logs, flap gates, flashboards, and dropping shutters, several different designs have been used at different installations [Davis and Sorensen, 1970: ch. 21]. Some of the flash- board designs are described in [Creager et al., 1945: ch. 24; Creager and Justin, 1950; and Barrows, 1943]. The designs of gates, hoists, and flashboards must be developed by experi- enced mechanical engineers or manufacturing companies. Energy d.issipators Gates 1-15 ASCEIEPRI Guides 1989 'Z Min. Freeboard+ --"----·-1"'1 100-Year Water Surface 5L. 2 Times o 50 Riprap 4 • Granular Bedding Channel Bed 3.0"Min.J ASCE/EPRI Guides 1989 Geotex"tlle <optional) 3 Times o50 Alprap / Rock Rip-Rap Geotextlle Fatric Bedding Layer (optional> Figure 1-10.-Typical riprap protection. 1-16 v .. · •' .. ... , : ~ (,' ._-...;· :_. ·_,·· Toe-in Trench =''' 'If,, ~/. _Ill""'" nt'"" "*" Q;.a \II 7 Figure 1-11.-Typical gabion walls. 1-17 ):( " 1(0 -~~,I If\::::. PERMEABLE \.a MEMBRANE ASCE/EPRI Guides 1989 ASCE!EPRI Guides 1989 a. Plan of spillway. "' <Z: :I ot-... g O<Z: WEIR EL 209.1 CREST I Zl- ''"" EL~i!W:c c .. .. I ~ ::! c ; I s •.01 / EL 193.6 I I ~ ~ :! :! c c .. .. .. i I s • .l3 I lL 111.7 ~ EL 111S.t I ~ I ~ + ~ . .... .... ---~ ~ c .. .. .. i I I b. Profile of spillway. =rJWl:, ~-WIIR CRIST OETA.IL A: •• 221 ... SECTION A.-A c. Weir geometry and pressure tap locations. Figure 1-12.-Labyrinth spillway. [ASCE, 1985]. 1-18 Semi-Circular Spillway at Lower Dam .... ----240'---- 80' Cl Cl Cl Cl Cl Cl Cl II:] II:] a:::::J a:::::J a:::::J [[J a:::::J Plan Figure 1-13.-Semicircular spillway. [USBR, 1980b]. MIGUEL HIDALGO SPILLWAY NEAR EL FUERTE, SINALOA, MEXICO DESIGN FLOW 580,480 cfs (16,450 m3/s} OI.ENSA SPILLWAY NEAR FRYOEK-MISTEK. CZECHOSLOVAKIA DESIGN FLOW 3,388 cfs (96m3ts} Figure 1-14.-Spillways with double-sided crests. [Prakash, 1987]. 1-19 ASCE!EPRI Guides 1989 Emergency evacuation Energy dissipation F. LOW-LEVEL OUTLETS For small hydroelectric installations, low-level outlets are sometimes used to perfonn the dual function of downstream release and emergency evacuation of the reservoir. However, there may be situations where two separate systems must be provided. Nonnally, hydraulic modeling is only required in complex hydraulic situations. The plan and sections of a typi- cal low-level outlet structure are shown on figures 1-4 and 1-15. For installations with barrages and timber or steel dams, a bay of the diversion structure may be used for emergency evacuation. In other cases, a low-level conduit with a cone valve at the exit end or with a slide-gate control at the inlet end may be provided. The ener- gy dissipation arrangements at the outlet end of the gates or conduit may be designed using the methodology in [USBR, 1978a: ch. 6; USBR, 1987: ch. 9; and DOT, 1975]. STCI'LOGSUTS PLAN OF lOW lEVEl INTAKE SECTION H 10 SCAl[ IH FU T NMNM.lOW WJ.. 6800' 20 5'·6' ~ S'·6' 15 SHUT OFF SLDE GATE 0 10 20 ScALE IN fEET SECTION THRU VALVE CHAMBER CONTINUOUS WlUUY 0 2 6 ~ SCALE IN fEET OUTLET TUNNEL Figure 1-15.-Sections of a typical outlet structure. [Mascolo, 1987]. ASCE/EPRI Guides 1989 1-20 G. SEDIMENT CONTROL The sediment transport characteristics of natural streams vary widely from region to region and season to season. It is therefore extremely difficult to develop satisfactory generalized designs of sediment control devices based solely on analytical or empirical formulas. Where silting of diversion dams or intake structures appears to be a potential problem, the design and performance of the proposed sediment control device should be verified by model experiments. The fundamental principles and conceptual designs of the different types of sediment control devices suitable for small hydroelectric projects are described in the following paragraphs [CBIP. 1971: ch. 5; Singh, 1967; and Moore, 1988]. In general, all the sediment control measures described in the sections on conventional hydroelectric installations apply to the dams and intakes of small hydroelectric installations as well. Other sediment control devices suitable for the power channel, intake, or diversion dam of a small hydroelectric power plant may include the following: • Submerged vanes • Guide banks and extended groyne walls • Skimming and cantilever platforms • Desiltation basins • Silt excluders • Silt ejectors or extractors • Undersluices • Low-level gabion, straw-bale, or haystack dams • Trashracks and screens For a new site, an attempt should be made to locate the intake of the power channel at the outer (convex) side of a river bend. Normally, open channels have a tendency to deposit sediment on the inner (concave) sides of the bends and maintain a relatively sediment-free deeper flow on the opposite side. An intake located at the convex side is likely to draw less than its proportionate share of sediment. Submerged vanes are thin vertical walls curved at a radius of 25 to 40 feet. They are pro- vided in the main channel to deflect the bottom silt-laden water to an angle of about 30 degrees from the direction of flow. The walls may be made of 3-inch-thick concrete or steel plates. Their height is 25 to 30 percent of the normal depth of flow, and their spacing is about 1.5 times the height. On the upstream side, the vanes should extend about 2 to 5 feet beyond a line drawn at an inclination of 2: 1 to the axis of the parent channel from the downstream edge of the intake, as shown on figure 1-16. On the downstream side, they should extend beyond the centerline of the intake. The dimensions of the submerged vanes should be finalized after adequate model testing. If the economics of a particular project permits, a concave-convex guide bank may be con- structed upstream of the intakes so that water may be withdrawn from an artificially con- structed convex bend in the stream, as shown on figure 1-17. The extended groyne wall, sometimes called "Gibb 's groyne wall," is an extension of the downstream wingwall of the intake structure into the main channel in the form of a smooth Sediment control devices Submerged vanes Concave/ convex guide bank Gibb's groyne well 1-21 ASCE/EPRI Guides 1980 Skimming platform Cantilever platform Silt excluder Silt ejector curve. The groyne wall is extended upstream into the main channel to cover about 75 to 100 percent of the width of the intake so as to divide the discharge of the main channel in proportion to the requirements of the power channel and the channel downstream. It is assumed that the sediment load is proponional to the discharge and is divided proportion- ately between the intake and the downstream portion of the main channel. If the power channel should receive less than its proportionate share of sediment, then the groyne wall is designed to diven extra water toward the intake and the surplus is released through an opening near the bottom of the groyne wall, as shown on figure 1-18. The skimming platform is a modification of the groyne wall. In this case the bottom floor of the intake consists of a raised crest and a concrete slab spans the space between the groyne wall and the crest of the intake to form a skimming platform. The curved groyne is provided only above the platform. Thus the flow passing between the crest of the intake and the groyne wall is divided by the cantilever platform into the silt-laden bottom ponion, which escapes into the main channel and the relatively silt-free top portion, which enters the intake. In addition, adjustable shutters may be provided with appropriate openings in the groyne wall to release surplus discharge into the main channel as in the case of the Gibb's groyne wall. The cantilever platform consists of a raised crest on the floor of the intake with a concrete cantilever slab extending into the main channel at a level approximately 1 foot below the crest, as shown on figure 1-19. The cantilever slab separates the top and bottom water. The relatively silt-free top water enters the intake and the silt-laden bottom water flows into the main channel. A desiltation basin is a depression provided in the power canal immediately downstream of the intake structure. It has gradually diverging walls to reduce the flow velocity to about 0.25 ft/s. An outlet is provided at the bottom of the basin to periodically flush the accumu- lated sediment out of the power canal. A well-proportioned desiltation basin is illustrated on figure 1-20 [Moore, 1988]. The design principles of desiltation or setting basins are given in [Oart, Veissman, and Hammer, 1977; Merritt, 1976; and Pembenon and Lara, 1971]. A silt excluder includes an intake with a raised crest and a number of gate-controlled tun- nels running nearly parallel to the crest of the intake with their tops forming a skimming platform at the elevation of the crest. The bottom silt-laden water is passed through the tun- nels at a high velocity of approximately 10 ft/s, and the relatively silt-free top water enters the intake. A sketch of the silt excluder is shown on figure 1-21. The silt extractor, or ejector, is a structure designed to extract and eject sediment that has already entered the power channel. In principle, it is similar to the silt excluder and is provid- ed in the power channel downstream of the intake structure. The entire width of the power channel is divided into three or four tunnels. The tunnels are curved at right angles so as to exit into an escape channel at one of the banks of the main channel. The widths of the tunnels are gradually reduced as they approach the mouth of the escape channel. In each main tunnel, partitions subdivide the tunnel into a number of smaller tunnels terminating near the exit of the main tunnel. The height of the tunnels is about 20 to 25 percent of the normal depth of flow in the power channel, and their roofs extend into the main channel for a distance of about 1.5 feet beyond their mouth. A typical silt ejector is illustrated on figure 1-22. ASCE/EPRI Guides 1989 1-22 ~~)L 1\r-~ I 12! I Jr I I Figure 1-16.-Submerged vanes. Figure 1-18.-Extended groyne wall. [Singh, 1967]. Right bank canal Concave-convex left guide bank left bank canals Figure 1-17.-Concave/convex guide bank. [CBIP, 1971]. Figure 1-19.-Cantilever platform. [Singh, 1967]. Pli\N PROFILE Figure 1-20.-Desiltation basin. [Moore, 1988]. 1-23 ASCE/EPRI Guides 1989 Undersluice Gabion and straw-bale (haystack) dams RI!CiUI.,ATOI'< CREST !.I::V~J . .. ' .. . ~. . ; I ('AN .. l " ( C "'A TQR C trNT --Q -· ._fi_ --0--~---lJ..)_ 0--0 --G--0--0--0--~, __ .,.. lfl v J:/f PLAN Figure 1-21. -Silt excluder. [Singh, 1967]. An undersluice bay is a bay of the diversion weir or barrage near the intake of the power channel. The crest and floor of this bay are about 2 to 3 feet lower than those of the other bays. It is separated from the other bays by a divide wall. The divide wall is an extension of the pier both on the upstream and downstream sides of the crest of the weir or barrage. The lower elevation of the floor of the undersluice bay tends to maintain a deeper pool of water in the portion of the main channel immediately upstream of the intake. The under- sluice bay is provided with gates that are operated to flush the sediment deposited upstream of the intake. If required, similar gate controlled openings may be provided in one or two other bays of the weir or barrage located near the center or other appropriate portions. Low-level submerged gabion and straw-bale (haystack) dams are small obstructions, tem- porary or permanent. constructed across the main channel upstream of the intake of the power channel. These structures trap bed load consisting of pebbles and rocks and sedi- ment and debris moving down the channel before it reaches the intake. The entrapped bed load is removed after the flood season or as required. Gabion dams are similar to, though smaller, than the structures described in section A. Haystack dams are illustrated on figure 1-23. The design information for trashracks and screens is described in Division II, Chapter 2, "Waterways." ASCEIEPRI Guides 1989 1-24 ..J < z .. " - LIN EO 'Se.C: T/Oi .. CIAP,..QAGM) C:ANAJ..~ SECTION AT xy 0 ,.. Figure 1-22.-Silt extractor, or ejector. [Singh, 1967]. H. RIVER DIVERSION DURING CONSTRUCTION The construction period for small hydroelectric installations varies from a single season to 1 or 2 years. In some cases, construction may be completed within the dry season and no diversion arrangement may be necessary. In other cases, river diversion may be required for a year or so. Diversion structures may be designed for 2-to 5-year flood events. Feasible river diversion arrangements include the following: • Earth dikes with riprap protection and a diversion channel or conduit • Gabions with impenneable membranes on the upstream face • Levees or guide banks with riprap protection • Inflated dams constructed of rubber or synthetic materials • Impenneable groynes • Temporary pipe culverts or box culverts • Fabrifonns or fabricast bags filled with fine-aggregate concrete • Sheetpile diversion dams 1-25 ASCE/EPRI Guides 1989 DOT FlOW---• Bambol~ place on the contour Straw bale check d.1111s. Figure 1-23.-Haystack, or straw-bale, dams. [Barfield et al., 1981]. The methodology for the design of these structures is given in [CBIP, 1970; Davis and Sorensen: 1970, ch. 8; DOT, 1965; AISI, 1981; and PCA, 1964]. I. REFERENCES AISI (American Iron & Steel Institute), Handbook of Steel Drainage and Highway Construction Products, Washington, D.C., 1981. ASCE, "Labyrinth Spillways," Journal of Hydraulics Engineering, March 1985. Barfield, B.J., Warner, R.C., and Haan, C.T., Applied Hydrology and Sedimentology for Disturbed Areas, Oklahoma Technical Press, Stillwater, Oklahoma, 1981. Barrows, H.K., Water Power Engineering, McGraw-Hill Book Co., New Yorlc, 1943. Cassidy, J.J., et al., "Boardman Labyrinth-Crest Spillway," Journal of Hydraulic Engineering, ASCE, March, 1985. CBIP (Central Board of Irrigation and Power), River Behaviour, Control and Training, Publication No. 40, New Delhi, India, 1971. ASCEIEPRI Guides 1989 1-26 Chow, V.T., Open Channel Hydraulics, McGraw-Hill Book Co., New York, 1959. Clark, J. W., Viessman, W., and H.ammer, M.J., Water Supply and Pollution Control, Harper and Row Publishers, New York, 1977. COE (U.S. Army Corps of Engineers), Hydraulic Design Criteria, Washington, D.C., 1959. COE, Hydraulic Design of Flood Control Channels, EM-111~2-1601, Engineering and Design, 1970. COE, Reservoir System Analysis for Conservation, HEC-3, Generalized Computer Program, The Hydrologic Engineering Center, Davis, California, 1974. COE, Recommended Guidelines for Safety Inspection of Dams, 1976. COE, Hydraulic Design Criteria, 1977. COE, Simulation of Flood Control and Conservation Systems, HEC-5, Generalized Computer Program, The Hydrologic Engineering Center, Davis, California, 1979a. COE, Feasibility Studies for Small Scale Hydropower Additions, The Hydrologic Engineering Center, Davis, California, 1979b. COE, HEC-2, Water Surface Profiles, Computer Program, The Hydrologic Engineering Center, Davis, California, 1982. COE, Hydropower, Engineering Manual EM-1110-2-1701, Engineering and Design (Final Draft), 1985. COE, Flood Hydrograph Package, HEC-1, Generalized Computer Program, The Hydrologic Engineering Center, Davis, California, 1987. Creager, W.D., Justin, J.D., and Hinds, J., Engineering for Dams, 2nd ed., Jolm Wiley & Sons, Inc., New York, 1945. Creager, W.D., and Justin, J.D., Hydroelectric Handbook, Jolm Wiley & Sons, Inc., New York, 1950. Davis, C. V. and Sorensen, K.E., Handbook of Applied Hydraulics, McGraw-Hill Book Co., New York, 1970. DOT (U.S. Department of Transportation), "Hydraulic Charts for the Selection of Highway Culverts," Hydraulic Engineering Circular No.5, Bureau of Public Roads, Washington, D.C., 1965. DOT, "Use of Riprap for Bank Protection," Hydraulic Engineering Circular No. ll, Federal Highway Administration, Washington, D.C., 1970. DOT, "Hydraulic Design of Energy Dissipators for Culverts and Channels," Hydraulic Engineering Circular No. 14, Federal Highway Administration, Washington, D.C., 1975. EPRI (Electric Power Research Institute), Simplified Methodology for Economic Screening of Potential Low- Head, Small-Capacity Hydroelectric Sites, EPRI EM-1679, 1981. Golze, A.R., Handbook of Dam Engineering, Van Nostrand, Reinhold Company, New York, 1977. Gordon, J.L., Parkinson, F.E., and Rakolondrafara, B., "Andekaleka Gathering Tube Hydropower Intake," Journal of Hydraulics Engineering, ASCE, 1987. Harr, M.E., Groundwater and Seepage, McGraw-Hill Book Co., New York, 1962. Hay, N. and Taylor, G., "Performance and Design of Labyrinth Weirs," Journal of Hydraulics Division, ASCE, November, 1970. IRI (Irrigation Research Institute), Hydraulic Design of Nanona Barrage, TM No. 33-44 (H 1-4), U.P., India, 1963. 1-27 ASCE/EPRI Guides 1989 Khosla, A.N., et al., Design of Weirs on Permeable Foundations, Publication No. 12, Central Board of Irrigation and Power, India, 1962. Leliavsky, S., Design of Dams for Percolation and Erosion, Chapman & Hall, Ltd., London, 1965. Linsley, R.K., and Franzini, J.B., Water Resources Engineering, McGraw-Hill Book Co., New York, 1972. Mascolo, R., "Preliminary Design of Sandstone Darn Low Level Outlet Works," Proceedings, Conference on Design of Hydraulic Structures, Colorado State University, Ft. Collins, Colorado, 1987. Merritt, F.S., Standard Handbook for Civil Engineers, McGraw-Hill Book Co., New York, 1976. Moore, E.T., Hydro Review, vol. VII, No. II, Hydro Consultants Inc., Kansas City, Missouri, April1988. NAP (National Academy Press), Safety of Dams, Flood and Earthquake Criteria, 1985. NWS (National Weather Service), Operational Dynamic Wave Model, U.S. Department of Commerce, NOAA, Silver Springs, Maryland, 1982. Paudial, G.N., and Yoder, R.D., "Design of Hydraulic Structures to Improve Farmer-Managed Irrigation Systems," Proceedings, Conference on Design of Hydraulic Structures, Colorado State University, Ft. Collins, Colorado, 1987. PCA (Portland Cement Association), Handbook of Concrete Culvert Pipe Hydraulics, Skokie, illinois, 1964. Pemberton, E.L., and Lara, J.M., A Procedure to Determine Sediment Deposition in a Settling Basin, Bureau of Reclamation, Denver, Colorado, 1971. Prakash, A., Arumugarn, C., and Jagadheesan, A., "An Experimental Investigation of Uplift Pressures," Hydraulics Division Specialty Conference, ASCE, University of Maryland, College Park., Maryland, 1978. Prakash, A., "Discussion on Boardman Labyrinth-Crest Spillway," Journal of Hydraulic Engineering, ASCE, June, 1987. Prakash, A., "Hydrologic Safety of Earth Darns," ASCE Conference on Hydraulic Engineering, Colorado Springs, Colorado, 1988. SCS (Soil Conservation Service), Hydraulics for Broad-Crested Spillways, Technical Release No. 39, 1968. SCS, Computer Program for Project Formulation Hydrology, Technical Release 20 (TR-20), Supplement No. l, U.S. Dept. of Agriculture, 1969. SCS, A Guide for Design and Layout of Earth Emergency Spillways as Part of Emergency Spillway Systems for Earth Dams, Technical Release No. 52, 1973. SCS, Urban Hydrology for Small Watersheds, Technical Release 55 (TR-55), U.S., 1975. SCS, Hydraulic Design of Riprap Gradient Control Structures, Technical Release No. 59, 1976a. SCS, WSP2, Water Surface Profile, Computer Program Technical Release No. 61, 1976b. Sherard, J.C., Woodward, R.J., Gizienski, S.F., and Oevenger, W.A., Earth and Earth-Rock Dams, John Wiley & Sons, Inc., New York, 1963. Simons, D.B., and Senturk, F., Sediment Transport Technology, Water Resources Publications, Fort Collins, Colorado, 1977. Simons, D.B., et al., Hydraulic Test to Develop Design Criteria for the Use of Reno Mattresses, Maccaferri Steel Wire Products, Ltd., Ontario, Canada, 1984. Singh, B., Fundamentals of Irrigation Engineering, Nem Chand & Bros., Roorkee, India, 1967. ASCE/EPRI Guides 1989 1-28 Terra Aqua, Inc., Flexible Weirs for River Training and Water Supply, Englewood, Colorado, 1983. USBR (Bureau of Reclamation), Design of Gravity Dams, Denver, Colorado, 1976. USBR, Design of Arch Dams, Denver, Colorado, 1977. USBR, Design of Small Canal Structures, Denver, Colorado, 1978a. USBR, Hydraulic Design of Stilling Basins and Energy Dissipators, Washington, D.C., 1978b. USBR, Reconnaissance Evaluation of Small, low-Head Hydroelectric Installations, Denver, Colorado, 1980a. USBR, Design of Small Dams, 3rd ed., Denver, Colorado, 1987. USBR, "Rehabilitation of Guajataca Dam," Puerto Rico Electric Power Authority, 1980b. USBR, Design of Small Dams, 3rd ed., Denver, Colorado, 1987. 1-29 ASCE/EPRI Guides 1989 CHAPTER2. WATERWAYS CONTENTS Section Page A. General design concepts .............................................................................................................................. 2-1 1. Small-scale hydro project design ............................................................................................................ 2-1 B. Intake structures .......................................................................................................................................... 2-1 1. 'fypes of intakes ...................................................................................................................................... 2-1 2. Hydraulic design ................................................................................................................................... 2-10 3. l)ebris control arrangements ................................................................................................................. 2-14 4. Icing problems ....................................................................................................................................... 2-17 5. Gates and valves .................................................................................................................................... 2-19 C. Power canals ............................................................................................................................................. 2-20 1. Sizing ..................................................................................................................................................... 2-20 2. Hydraulic design ................................................................................................................................... 2-21 3. Linings ................................................................................................................................................... 2-22 4. Appurtenant structures .......................................................................................................................... 2-22 D. Penstocks and conduits ............................................................................................................................. 2-23 1. 'fypes and materials ............................................................................................................................... 2-23 2. Hydraulic design ................................................................................................................................... 2-23 3. Structural requirements ......................................................................................................................... 2-41 4. Protective valves, gates, and appurtenances ......................................................................................... 2-43 5. Protective coatings for penstocks .......................................................................................................... 2-44 E. Tailrace channels ....................................................................................................................................... 2-45 F. Hydraulic modeling ................................................................................................................................... 2-49 G. Downstream fish passage ......................................................................................................................... 2-49 1. General .................................................................................................................................................. 2-49 2. 'fypes of fish screens ............................................................................................................................. 2-50 H. Upstream fish passage .............................................................................................................................. 2-62 1. General .................................................................................................................................................. 2-62 2. 'fypes of fishways .................................................................................................................................. 2-62 3. Selection of upstream fish passage ....................................................................................................... 2-68 I. Instream fishery mitigation and habitat improvement ............................................................................... 2-70 1. General .................................................................................................................................................. 2-70 2. Structures and methods ......................................................................................................................... 2-71 J. References .................................................................................................................................................. 2-74 TABLES Table 2-1 1'ypical entrance loss coefficients ......................................................................................................... 2-11 2-2 Laterally unsupported lengths of steel trashrack bars ........................................................................... 2-15 2-3 Head losses through trashracks ............................................................................................................. 2-17 2-4 Free-discharge coefficients for gates and valves .................................................................................. 2-20 2-5 Permissible velocities and side slopes for earthen power canals .......................................................... 2-20 2-6 1'ypical Manning's roughness coefficients forchannels ....................................................................... 2-21 ASCE/EPRI Guides 1989 CONTENTS -Continued Table 2-7 Characteristics of selected pressure pipes ............................................................................................. 2-24 2-8 Pipe roughness values, k ....................................................................................................................... 2-27 2-9 Allowable bearing pressures for different soils .................................................................................... 2-43 FlGURES Figure 2-1 Intake with raised sill .............................................................................................................................. 2-2 2-2 Aumed intake with raised sil1 ................................................................................................................. 2-3 2-3 Perforated pipe intake ............................................................................................................................. 2-3 2-4 Catchment basin type intake ................................................................................................................... 2-4 2-5 Through-the-bank type intake ................................................................................................................. 2-5 2-6 Culvert pipe intake -plan and sections ................................................................................................ 2-6 2-7 1'ypical intake gating arrangements ........................................................................................................ 2-7 2-8 Velocity cap intake -section and operation .......................................................................................... 2-8 2-9 General layouts of typical intake structures ............................................................................................ 2-9 2-10 Symmetrical and lateral approach flow conditions ............................................................................... 2-13 2-11 Devices to minimize potential for free-surface vortices ....................................................................... 2-13 2-12 Frazil ice production and supercooling ................................................................................................. 2-17 2-13 Diagram for determining the Darcy friction coefficient.. ..................................................................... 2-26 2-14 Loss at sudden expansion ..................................................................................................................... 2-28 2-15 Loss at conical expansion ..................................................................................................................... 2-28 2-16 Loss at sudden contraction .................................................................................................................... 2-28 2-17 Intake losses .......................................................................................................................................... 2-31 2-18 Definition sketch for hydraulic transient analysis ................................................................................ 2-32 2-19 Surge tank definition diagram ............................................................................................................... 2-34 2-20 Relief valve operation at power plant ................................................................................................... 2-36 2-21 Waterbammer chan for uniform valve closure ..................................................................................... 2-40 2-22 Waterbammer for valve opening ........................................................................................................... 2-40 2-23 Tailrace design to prevent erosion ........................................................................................................ 2-46 2-24 Tailrace fish barrier (1) ......................................................................................................................... 2-47 2-25 Tailrace fish barrier (2) ......................................................................................................................... 2-48 2-26 Stationary screen with brushing mechanism ........................................................................................ 2-51 2-27 Paddle wheel screen .............................................................................................................................. 2-51 2-28 Inclined stationary screen ..................................................................................................................... 2-53 2-29 Powerhouse intake structure with fishscreens ...................................................................................... 2-53 2-30 Pressure wedge-wire screen in turbine penstock .................................................................................. 2-53 2-31 Coanda screen ....................................................................................................................................... 2-55 2-32 Cylindrical wedge-wire screen ............................................................................................................. 2-55 2-33 Drum screen-elevation view ............................................................................................................ 2-56 2-34 Rotary drum screen ............................................................................................................................... 2-57 2-35 Installation of bar screen in turbine intake ............................................................................................ 2-58 2-36 Submersible traveling screen at turbine intake ..................................................................................... 2-59 2-37 Schematic of submersible traveling screen ........................................................................................... 2-59 ASCE/EPRI Guides 1989 ii CONTENTS-Continued Figure Page 2-38 Louvers ................................................................................................................................................. 2-61 2-39 Louver vector analysis .......................................................................................................................... 2-61 2-40 Schematic of Denil fishway .................................................................................................................. 2-63 2-41 Typical weir and pool fishway .............................................................................................................. 2-63 2-42 Typical weir and pool fishway, modified ............................................................................................. .Z-65 2-43 Ice Harbor weir crest. ............................................................................................................................ 2-66 2-44 Dimensions of pools at Cabot Ladder, Connecticut River ................................................................... 2-67 2-45 Venical slot fishway .............................................................................................................................. 2-67 2-46 Elevator design ..................................................................................................................................... 2-69 2-47 Fish lock system .................................................................................................................................... 2-69 2-48 Fish lift system ...................................................................................................................................... 2-70 2-49 Hewitt Ramp ......................................................................................................................................... 2-72 2-50 Rock deflectors ..................................................................................................................................... 2-72 2-51 Effects of deflection on stream flow ..................................................................................................... 2-73 2-52 Dimensions for deflectors ..................................................................................................................... 2-73 The "Waterways" chapter was written by: Anand Prakash, Ph.D., P.E. Chief Water Resource Engineer Dames and Moore 1626 Cole Bouleverd Golden, Colorado 80401 Thomas H. Logan, P.E. Consultant 1310 Wadswoith Boulevard, Suite 100 Lakewood, Colorado 80215 Head, Penstocks Section, USBR (Retired) CREDITS iii Ronald F. Ott, Ph.D., P.E. Ott Water Engineers 1412 !40th Pl. NE Bellevue, Washington 98007 Charles E. Bohac, Ph.D., P.E. Tennessee Valley Authority 2S 270C Haney Bldg. Chattanooga, Tennessee 37401 ASCE/EPRI Guides 1989 CHAPTER2. WATERWAYS A. GENERAL DESIGN CONCEPTS 1. Small-Scale Hydro Project Design The designs of water conveyance structures for small-scale hydro projects are basically the same as those for conventional hydroelectric projects. However, the ratio of the costs of these structures to the total cost of the project may be significantly different for the two cases. Therefore, the considerations for the selection of the mode of water conveyance; for the selection of the alignment, location, and design of the various components of the water conveyance system; and for the selection of construction materials for the waterways of a small-scale hydro project can be different. In some cases, an existing ditch, drainage, pipeline or intake may be used as part of the water conveyance system for a small hydropower project. In these situations, the dimen- sions and designs of the existing structures should be checked for adequacy, structural integrity, and safety. If necessary, the existing structure should be modified and rehabilitat- ed to meet the requirements of the proposed project. 'The methods and criteria to check the designs of the existing structures are the same as those for new structures. The various structural elements of the water conveyance system for a hydroelectric power- plant include the intake structure, power canal or power conduit, penstock, surge tank or forebay, tailrace, and structures to facilitate the safe movement of fish through the project. The engineering considerations for these structures are presented in the following sections. B. INTAKE STRUCTURES 1. Types oflntakes The different types of intakes suitable for small hydroelectric projects include the following: • River intake with a raised sill where the entry of water into the power canal may be controlled by gates or stoplogs. This intake is illustrated on figures 2-1 and 2-2. These intakes are suitable for rivers with significant bed load movement and reser- voirs with potential for sediment deposition at the location of the intake. The raised sill prevents the sediment bed load from accumulating and blocking the intake when some suitable means is provided for purging the accumulated material from time to time. • Perforated pipe intake where water is withdrawn from a river or lake through one or more perforated or screened pipes [Richards and Hroncich, 1976). A schematic of this intake is given on figure 2-3. These intakes are suitable for locations where low approach velocities and fish protection are major concerns and bed load movement is relatively low. Project design concepts Intake structures 2-1 ASCE/EPRI Guides 1989 Intake structures 1 HALF PLAN 0 l..,... . e-141&. H·~·;....----"~---· I.-S~~TION Figure 2-1.-Intake with raised sill. • Catch basin or through-the-bank type river intake with a pipe outlet as shown on fig- ures 2-4 and 2-5. These intake structures are suitable for diversion of water from shallow streams or the stream or supply channels. A portion of the water flowing through the stream or supply channel is caught into a catch basin located immediately upstream of the pipe which runs through a bank of the parent channel. In the case of a river intake, a steel grating may be provided on the top of the catch basin to prevent debris from entering the intake [USBR, 1978: ch. III; Anans, 1985]. • A culvert pipe river intake is shown on figure 2-6. These are miscellaneous types of intakes suitable for specific site conditions. The one illustrated on figure 2-6 has a catch basin connected to an existing pipe culvert. The catch basin discharges into a squash culvert connected to a concrete chamber which discharges into the pressure pipe leading to the power plant. • Vertical tower intake with screened or open inlets for rivers and reservoirs as shown on figure 2-7. These intakes are used on earth dams or rivers where the abutments or banks are not suitable for the construction of intake structures and for concrete dams where the intake must be located on the abuonent. If required, these intakes may be used for selective withdrawal of water by providing inlet ports at different elevations along the periphery of the vertical tower. • A velocity cap type intake for lakes, reservoirs, and rivers is illustrated on figure 2-8 [EPA, 1973]. The underwater velocity cap in this type of intake ensures horizontal flow velocities at the entrance and thus minimizes the entry of fish into the intake. If required, a steel cage may be provided along the rim of the intake pipe to prevent debris from entering the intake. ASCE/EPRI Guides 1989 2-2 j_ T ()JSTRIIJVTARY L-SECTION OIST~I BIJT .tRY 11 ROAQ T PLAN Figure 2-2. -F1umed intake with raised sill. u.JF=ICTR:&:o.."TlOt-...~ :::.~s (-....JEL...L. ~ew 'T'{PE) Figure 2-3. -Perforated pipe intake. Courtesy Ott Water Engineers. 2-3 ASCE/EPRl Guides 1989 II' LOHO IY II' WIDE OAA TE COHCAE TE BOX ITRUCTURI PROFILE TYPICAL GRATE 'BARS' Figure 2-4. -Catchment basin type intake. I' WID! flAHOE BEAM • Inclined pipe intakes for rivers and reservoirs are suitable for earth dams or rivers where the inclined pipe can be supported on the slope of the embankment or river bank and selective withdrawal of water at different elevations is required due to envi- ronmental considerations. • Vertical submerged structures are sensitive to seismic forces -such is the nature of dynamic forces that they cause both positive and negative pressures on the structure. The general layout of a typical intake structure is illustrated on figure 2-9. The type and layout of the intake structures will differ from project to project. Depending on the site conditions, the intake may be located several miles upstream of the powerhouse on a high- head project, as an integral part of the powerhouse on low-head systems, or in a deep reser- voir upstream of an existing dam. In any case, the location should be floodproof or such that adequate flood protection may be provided at reasonable cost. Technical considera- tions for the siting of intakes are included in [Mosonyi, 1963: vol. I, pp. 227-236; ASCE/EPRI, 1989b]. Some information on intake designs to minimize cost and maximize output is presented by Gordon et al. [ 1985] and Moore [ 1988]. ASCE/EPRI Guides 1989 2-4 tT-- ---------AL'.-=:.....1--+++----+-lflem~··...i-=:!!'" ~H---- ' ' ll' ··•• .... , ct.;: lent ,_ .. ,. •"' her ... ..., ................ taoCII\,.tlt ... QIICIIIOI"IIOitlft ........ N ,., ' l '' '' '' CD ---f-t ' .... ' ~ ... ,. ..... 7 SECTION B-B ... _ (,.._....,,_ati'...,.H SECTION A-A ........... _, ..... , .. o, ~~~ar' ,..,. .. ,.. CIMCI'e,. AIR VENT DETAIL NOTES c • rwr,..., qote .,... .,. ..... ..,.., ... •• e»• .. c_.. ..... DtOt d ...... , .. ,,,.., 0 " ........... .._,.., '"' ,...., •• u...-d dloii!H_. ,.,. IAOff .,. ...... Go,. fP'OIRe ,....,., "'"~" ooo.. ( of ,..,. _..... Figure 2-5. -Through-the-bank type intake. [USBR, 1978]. 2-5 ASCEIEPRI Guides 1989 EXISTING 24.CULVERT EXISTING ROAD ASCE/EPRI Guides 1989 a. Plan. 241 x 38.CULVERT b. Sections. 151 VALve AUTOMATIC SHUTOFF GATE Figure 2-6. -Culvert pipe intake -plan and sections. 2-6 ,,, ............... __ t > en ~ Cl c 0: (II v. ....... \0 00 \0 ll a z 0 w "' ;'! !: ... ~ _. .. _. _. .. ll .. lr ... ll ... "' .. .. z 0 ... " i ... .. '3 .. "' ~ .. .. _. SCH[MATIC ILLUSTRATION FLOW OIR[CliOII - r--'"" HOISI·""· .. : tot ;.-·H<><sl HO<>it Reser volt' w s-., 1'-ll 1 I ··A.-llfnl e. alreom stols -. ~r_.v, .. e ... ror ~ -JI[·I~·~-~--~ Qoles ••tb up- · · ·f ul long lh went ' for downstream Curlou> WQII-- Trashrack····· uols :·?·"·lntcrmedtoft ·Corulu1l TYPE Ruervoll" w Sw~~ Slol Stoptogs·· · Nolo lhol lloplogs must stock to o much greater heoghl of a dup curlo1n oral IS not uud os "' Type 8 obowe Troshrock----.. Whetl G< Role<· Mounted Gale··· • Stem Stchons Whttl or Ralltr- Mounltd Galt n=r-·P•pe s:~ .. ~-~-j~ ... ·, C:;:.t,· · ironsolion TYPE 8 HOUSUl9 Hoosl Noun···· ) ' t.loa w S ol whiCh Bulkhead -1 Fill / con be used for unwotenng .• Cur loin Wol· • '!I. · lroshrod.--. NOT£5 ANO COMMENTS lntoke ljpt$ used pr111copo1ty on con· crete dams ond on torth dotns w1lh abutment •nlokes. TjPe A uud pnmorft for s1ng1t w out It I works lJP• 8 uud lor oM IJPU of power outlets ond for branched ond mon1fald type or outlet works Type of in I okt frequently ustd on lhin·orch concrete dams Used for. ott l1pe. of powor out· lets ond lor brooch· td ond monilotd outlet works Goolry crone IS usuoMy pro- wldrd lor hondi"'Q gale ond sloplogs lor multiple oullel instolohons . lnlokt ustd moonly for obullfttnl onloktl on earth doma HOisl llems must be pro· Ytdtd with supporl wheels Reduchon 1n etrechve we1gnl for gro"l J closon9 moy require IN! prowtsKin of ciOSiilQ lhrusl bJ the ho1sl • or the use or ··oler ·mounttd gotes .. a " .. _. "' .. ,. :! :.l 5 "' " ;'! !: a: "' ~ ;; ... .. .. .. "' 0 "' J ,.. I! "' " ;'! I a: "' g ;;; ~ ! :I .. "' .. ... .. .. , ., "' " "' "' :I .. , !! ... ... ~ .. H015t--~~ ••• Reurvmr w S:~~ .... Cur tom Troshrock-·----> Oulkheod Golt·--·-·-·· Whul or Roller- Mounted Gate----·- ,-Orodqe to Oom :' or Abutment I .... ~.-~ HOist----L---1 Reservotr ws.-~ ... ~. ~ ~..r-. ,, -... - ,·llrod9e to Oom { or Abutment Aor Vents------;:- Troshrock · --~ ~ ~-> C yhnder Gate·----- ;' ~ [)om .-·RUttvOif W.$:-~, ,·Removoble Troshrock to \ perftlll ~nstol1n9 Bulkhead --lnto~e Structure -Trashrack · · ·Corculor Oulkheod Gote ·tloost Stem Sechons Figure 2-7.-Typical intake gating arrangement. (Davis and Sorensen, 1969]. ltOT[S AltO COM,.Eitnl Tower mlo~ts ore u~td pr 1nc: •Potly on eorlh d&.-ns •here obutme~ts ort not $llltoblt for tntoke s~ruch.~res Also used for concrete doms where W'ltokes must be ~ocoted on obulments ood 01t1er lypts ore not •rntoiJe 8oste Oftonqement 15 '$1mllor to verl1cof obulmenl 14\lo~e Bndqe 1s usuollr prowtded to dom or abutment rower Intake used prunor1ly where 1nlokt entrance 1S verflCOI Other selection toctors ore suntlof to lhose sloted obowe for ~erhco• towers. for feclonqulor qoles lntokt orron~tmtnt u~ed prmctpaly on eor lh dams Sholl usuoQy tocoled ntor OlliS. of dorn, ttl her lfl dom Of abutment Abutment tocollon iS preftH)ble lo OYO«d JOtnl Del ween abut- ment rot~ and dom f ,. 1otoke Bvlkheod mstaliohon reqwrts dr0*1nq reservotr down or plocemeflt from a borqe ond the employment of dlllff'S Manual line Screens Inle 7 t. ~ ,...~1 structu" / " ---uu--~ \~ ~~~~ l---~~· ~·~·~/-~~,~·'--------------------~ Inlet Condui a. Intake section. I Velocity Cap J Canal to Plant ( Velocity Distribution Without Cap Velocity Distribution With Cap b. Intake operation. Figure 2-8.-Velocity cap intake-section and operation. [EPA, 1973]. ASCE/EPRI Guides 1989 2-8 a. Layout a. b. Layout b. Figure 2-9.-General layouts of typical intake structures. Courtesy Ott Water Engineers. 2-9 ASCE/EPRJ Guides 1989 Intakes Flow computation Flow equations 2. Hydraulic DesiJPI a. Intakes. -An important consideration in the hydraulic design of intakes for small head hydroelectric projects is that the head loss during the passage of water from the parent channel to the power canal or power conduit is minimized. The intake design should avoid abrupt and supercritical contractions and expansions, large drops, and abrupt entrance con- ditions. The hydraulic design criteria for subcritical and supercritical channel transitions are given in Open Channel Hydraulics [Chow, 1959: ch. 7]. The head loss through a drop structure is the difference in the total energy lines on the upstream and downstream sides of the drop The methods for hydraulic computations associated with a drop structure are given in Design of Small Canal Structures [USBR, 1978: ch. 2] and Open Channel flow [Henderson, 1966: ch. 6]. The loss coefficients for typical inlet conditions are given in table 2-1 [AISI, 1971 and 1980; Brater and King, 1976; and USBR, 1987: ch. 10]. b. Flow Computation.-The total head loss through the intake structure must be known to estimate the net head causing flow and therefore the discharge that can pass through it with different water surface elevations in the parent channel or reservoir. Whereas physical and computer models may be required to analyze the hydraulics oflarge intakes, simple trial and error procedures are usually adequate for preliminary design of intakes for small hydroelec- tric projects. 1be computational steps of one such procedure for an open channel intake are given below: • For a given water surface elevation in the parent channel or reservoir, guess a trial water surface elevation downstream of the intake. • Compare the downstream water surface elevation with the elevation of the sill of the intake and determine if the flow will be free or submerged. • If the breadth of the horizontal portion of the intake sill along the direction of flow is more than twice the head of water above it, treat it as a broad-crested weir; otherwise assume it to be a sharp-crested weir. • Estimate a trial discharge using one of the following equations, as applicable [Lewin, 1958: ch. 5; Brater and King, 1976: ch. 5]. • Typical entrance loss coefficients are given in table 2-1. 1. Free Flow Condition Broad crest: Q = 3.CY:JLH 312 2 ~ 3/2 Sharp crest: Q = 3Cd v 2 g (L-o. 1 n H)H where H = head above crest in feet. 2. Submerged Flow ASCE/EPRI Guides 1989 2-10 where: Q = L = n = discharge through the intake (ft3/s), total open span of the intake (feet), number of end contractions, H = difference in head between the water surface elevations upstream and downstream of the intake, Cd= coefficient of discharge (may be 0.6 for sharp-crested, and 0.8 for broad-crested weirs), d = difference between the water surface elevation downstream of the intake and sill elevation, and g = gravitational acceleration (ftJs2). Table 2-1.-Typical entrance loss coefficients.• Entrance type Slightly rounded entrances Fully rounded entrances Square-cornered entrance flush with wall Square-edge wingwalls Headwall with rounded edges or rounded entrance Mitered pipes or sloping side walls to conform to fill slope Conduit, or intake walls projecting from fill, or inward projecting, square-cornered entrance Beveled entrance Circular bellmouths at conduit entrances Square or rectangular bellmouths at conduit entrances Head loss coefficient 0.23 0.10 0.5 0.5 0.2 0.7 0.9 0.25 0.05 0.16 • These loss coefficients are adequate for preliminary computations. See also [USBR, 1987]. Alternative equations for submerged and free flowover sharp-crested weirs unless are given in [Brater and King, 1971]. If the intake submergence is such that free-surface vonices develop with their crotches extending significantly beyond the pipe inlet, then the intake flow may be estimated using the orifice, weir, and open-channel flow equations modified for the shapes of the pipe inlets as appropriate [Chow, 1959: chs. 6 and 9; Brater and King, 1971: ch. 5]. If the intake is located in close proximity to the powerplant, inadequate submergence may result in the development of vortices which tend to reduce the discharge coefficient of the inlet and the efficiency of the turbine and may pull floating debris into the turbine. Empirical equations and guidelines to determine minimum required submergence to avoid the development of free surface vonices have been proposed by Gordon [1970]; Gulliver, et al. [1983 and 1986]; and Zielinski [1974]. For small intakes where hydraulic modeling is not economically feasible, these equations and guidelines may be used. A summary is given below. Entrance loss coefficients Intake submergence Intake vortices 2-11 ASCE/EPRI Guides 1989 Submergence Transitions where: S = minimum required submergence measured above upper lip of the bell mouth (feet), V = velocity through the intake measured at the gate or through the penstock (ft/s), d = diameter of the intake pipe or penstock (feet), and C = a coefficient equal to 0.3 for symmetrical and 0.4 for lateral approach flow conditions. For horizontal intakes with a vertical bellmouth inlet, the minimum submergence is given by: where: V0 = Intake velocity at the bellmouth (fils), Sn = Submergence measured above the centerline of the bellmouth (feet). Another criterion for the vortex free operation of horizontal intakes with vertical bellmouth inlets is as follows: For vertical intakes the following range of submergence has been suggested: where: s vo d s 0. 7 and r::;-s 0.5 ygd Some modifications to the inlets of intakes which may be useful in minimizing the poten- Vo F=.vgd tial for the development of free-surface vortices are shown on figures 2-10 and 2-11. As a rule, abrupt intake transitions should be avoided because such transitions may induce a strong vertical down-flow at the face of the intake with potential for vortex formation. The preferred outline for the approach channel to an intake along with that for an undesir- able abbreviated asymmetrical approach channel is shown on figure 2-lOa. Another pre- ferred layout which minimizes abrupt changes in velocity is shown on figure 2-lOb. Both these configurations avoid conditions which may lead to the formation of free-surface vor- tices [Moore, 1985]. ASCEIEPRI Guides 1989 2-12 a. Symmetrical and Asymmetrical b. Lateral Figure 2-10.-Approach flow conditions. [Gordon, 1970]. y G= to INVERTED INLET WITH SUCTION 6ELL ~ ([) I FLOW SPLITTER OR CROSS IN FLOOR DRAIN Figure 2-11.-Devices to minimize potential for free-surface vortices. [Zielinski, 1974]. 2-13 ASCE/EPRI Guides 1989 Intake locations Debris control methods 3. Debris Control Arrangements Depending on the size of the parent channel, debris control arrangements developed for conventional hydropower are also suitable for small-scale hydro installations. As far as possible, intakes should be located as close to the spillway as possible. The preferred orien- tation is when the intake headwall makes an angle of 90° to 100° with the axis of the spill- way so that the trash is removed by frequent flood flows passing over the spillway (see fig. 2-1 0). If the face of the intake must be coincidental and parallel to the upstream face of the spillway or overflow weir, it should be located adjacent to the spillway. This allows the operator to push some of the larger trash away from the intake and over the spillway during high floods. Intakes located in a dead comer away from the spillway tend to accumulate trash, which must be removed by periodic maintenance [Moore, 1988]. Some of the debris control devices particularly suitable for smaller intakes and smaller streams include the fol- lowing: • Debris control dams located in the parent channel a few hundred feet upstream of the intake structure. These are low head structures like timber trestles; beaver dams; check dams made up of pervious rock; straw bale barriers; and timber barriers with filler fabric, brush, or rock dikes that permit turbulent seepage to pass through them. Access should be provided to the small catchment basins crested to permit periodic cleaning using a front-end loader and dump truck [Barfield et al., 1981: ch. 7]. • Floating booms, log booms, or rock-training beams installed across the channel immediately upstream of the intake structure. • Trashracks made up of vertical or slightly inclined 2-to 4-inch-diameter wooden logs placed parallel to each other and bolted to horizontal wooden beams at top and bottom and in between as required from structural considerations. The spacing between the logs may vary from 3 to 6 inches depending on the size of trash carried by the parent channel or hydraulic requirements of the water passages of the selected turbine. A walkway is provided across the top to permit periodic cleaning. • Trashracks made up of vertical or slightly inclined circular or rectangular steel bars placed parallel to each other welded or bolted to horiwntal steel beams at top and bottom and in between as required from structural considerations. The spacing between bars may vary from 3 to 6 inches depending on the nature of debris trans- ported by the parent channel. A walkway is permitted to permit cleaning. • Bird-cage removable trashracks designed as cylindrical caps made of steel wires to be fitted on top of vertical pipe intakes. • An ungated barrier wall constructed across the forebay channel or across the approach channel upstream of the intake with submerged openings above its base. The wall starts from the end of the spillway or diversion dam and extends upstream across the approach channel. The well-submerged openings prevent trash from entering the approach channel upstream of the intake and the height and orientation of the barrier wall ensure that flood flows carry accumulated trash to the spillway. The submerged openings may be dimensioned to have a maximum flow velocity of 2 ft/s to prevent fish from being sucked into the intake. ASCE/EPRI Guides 1989 2-14 Some special guidelines for the design of trashracks include the following: • The open area in the rack should be such that the maximum velocity through the trashrack does not exceed 2 ft/s to avoid attraction of floating debris to the trashrack. • The trashrack should be removable for repair and maintenance. Where debris is a severe problem, relatively simple automatic or semi-automatic mechanical rakes may be installed. Usually, trashracks are custom designed and built. • The logs, bars, or wires and the frame of the trashrack should be designed to with- stand the hydrostatic and vibration-induced forces expected when the trashrack open- ings are plugged up to 50 to 60 percent with debris or ice, and also the drag forces associated with the obstructions to flow provided by the trashrack. • The openings in the trashrack should be as large as possible subject to the condition that floating debris transported by the parent channel do not pass through them. • To facilitate the cleaning operation, the trashrack should be inclined at an angle of 5° to 15° from the vertical. • The trashrack should be located away from channel transitions so that there is mini- mum turbulence and nearly uniform velocity distribution before and after the rack. At the same time, it should not be located in a stagnant area where there is potential for the growth and accumulation of algae or in an area where prevailing winds may drift debris into the rack. • If the trashrack is made up of steel bars, care has to be taken to design it so as to mini- mize vibrations. For small intakes with flow velocities of 2 ft/s or less through the trashrack, the limiting laterally unsupported length of steel bars may be taken from table 2-2 [Davis and Sorensen, 1970, ch. 24]. • The bar opening must also be sized relative to the opening between the turbine blades. Table 2-2. -Laterally unsupported lengths (in inches) of steel trashrack bars. Bar thickness, For velocity through net For velocity through net inches area of racks = 2 ftls area of rack = 1.5 ft/s 1/4 20 22 3/8 30 35 1/2 40 46 5/8 50 58 3/4 60 70 7/8 70 80 1 80 84 For larger intakes, appropriate structural analyses should be conducted to determine the unsupported lengths of trashrack bars. Trashrack guides Unsupported length 2-15 ASCE/EPRI Guides 1989 Spacing of bars Trashrack head loss • The spacing of trashrack bars should be as large as feasible and the thickness as low as practicable to minimize head losses. The head loss through trashracks depends upon the shape, size, and spacing of bars and the velocity of flow. [USACB, 1959] presents curves for head loss coefficients for trashracks with different types of bars oriented perpendicular to the line of flow and protruding above the water surface. For small intakes where model testing is usually not justifiable, the following formula may be used to estimate the head loss through the trashrack [Chow, 1979, ch. 7; Davis and Sorensen, 1970, ch: 24]: 4/3 2 h = k( ~) ; g sin a where: h = head loss through the racks (feet), t = thickness of bars (inches), b = clear spacing between bars (inches), v = velocity of approach ahead of rack (ftJs2), g = acceleration due to gravity (32.2 ft!s2), a = angle of bar inclination to horizontal (degrees), and k = a coefficient with a value of 2.42 for bars with square nose and tail and l. 79 for round bars. The head losses given by this formula are applicable to clean racks. The head losses for partially clogged racks may be taken to be higher than these. The Bureau of Reclamation's equation to estimate the head loss coefficient for trashracks is as follows [USBR, 1987: ch. 10]: where: K1 = trashrack loss coefficient, an = net area through the rack bars, and a8 = gross area of the rack and supports. For a conservative estimate of the head loss, the trashrack should be assumed to be 50 per- cent clogged. As an approximation, the following values of head losses shown in table 2-3 may be used for different velocities through clean trashracks [Davis and Sorensen, 1970: ch. 22]. ASCE/EPRI Guides 1989 2-16 4. Icing Problems Table 2-3. -Head losses through trashracks. Velocity through the rack, ftls 1.0 1.5 2.0 Head loss, ft 0.10 0.30 0.50 Icing problems at hydropower intake structures are usually caused by frazil ice and are similar for small, pumped storage, or conventional hydroelectric powerplants. Large intake grates or bar screens can be quickly and completely blocked when frazil ice fonns in the flowing stream, upstream, and impinges on the gate. Frazil ice fonns in turbulent flows where the water is super-cooled at a rate of about 0.03 to 0.1 °F/min. If an intake is locateddownstream from a section of water that can undergo rapid cooling, frazil ice is likely to be a problem (fig. 2-12). .. 0: :> ~ .. .. .. .. s .. ~ .. .. .. " Q ..... '-'o: ""' 0 1-I S 0 .. : ll ... ... 0 u -., -::! ~ t,Q "'" "O 0: .. ... 0 "-0 00 ~ Q: Q_$ ..... ;:)0. 0 .. 0 I I I / / / / ' TIM(, MIN . .u ~ DC -=·! ... 0, 0 -o -. 2 a. . 11'1 RATE OF WAT!R COO~ING •c/IIIN. Figure 2-12.-Frazil ice production and supercooling. [Logan, 1974]. ,01 Icing problems Frazil ice production 2-17 ASCEIEPRI Guides 1989 Frazil ice formation Intake design Solutions to ice problems Frazil ice fonns over a very shan period of time, but conditions exist such that quantities can be fonned rapidly when the proper atmospheric conditions exist. Immediately after fanning, frazil ice is in the active state where it will readily and quickly adhere to many materials, especially metal. The critical period for intake plugging is during the active peri- od. The temperature of water stans to increase as soon as the ice starts to fonn because of the heat given off on ice fonnation. Tilis eventually results in an inactive period when the water temperature returns to 32 °F. Because of the small size of ice panicles, in the inactive state they will usually pass through a grate or screen without plugging. Before designing the intake, it may be desirable to check local climatic conditions and the perfonnance of other intakes in the area with particular reference to icing problems. Average daily temperatures are not sufficient to detennine the potential for frazil ice fonnation. One must examine the daily fluctuation during the day and night during cold spells. Frazil ice can usually be seen by examining the stream when it is below freezing at night For verification of the potential for frazil fonnation a chain or pipe with a metal weight on it may be suspended into the water. On a clear, cold day frazil ice will adhere quickly if it is in the active state. Some of the solutions for frazil ice problems panicularly suited to small hydroelectric installations include the following: • Use a well screen buried in a sand-gravel bed in the stream. • Use a surface, nonmetallic "boom," which skims the floating ice off the stream and away from the intake or screen. Frazil ice usually remains near or at the water surface. • Heat the intake, trash rack, or screen when the stream temperatures approach 32 °F. Field experience indicates that around 200 watts per square foot of actual screen or trashrack metal surface will prevent the ice from adhering. Various coatings, such as ureathane and teflon have also been used to prevent the ice from adhering to the metal in the screen. • Avoid locating the intake immediately downstream from steep, shallow reaches of the stream which promote the high heat loss necessary for frazil ice fonnation. • Frazil ice seldom fonns in lakes or ponds where an ice sheet can develop. Thus, if a small reservoir can be fanned over the intake, frazil ice will probably not be a prob- lem. Tilis reservoir should be large enough so that the surface is quiet and a sheet of ice fonns when the air temperature drops below freezing. Frazil ice will not fonn under this sheet of ice. • When ice begins to fonn, the plant output should be reduced such that the velocity in the forebay, approach channel, or power canal is S' 2 fils, and the discharge should be held constant until an ice sheet is established over the entire surface. ASCE/EPRI Guides 1989 2-18 5. Gates and Valves Depending on the size of the intake, the gates and valves used for small hydropower installa- tions are generally the same as those used in conventional hydro practice. Gates for the intakes of small hydroelectric projects may be "off the shelf' items supplied by different manufacturers or custom-built using timber or steel. Some of the gates and valves particularly suited to the relatively smaller intakes for small hydroelectric projects include the following: • Stoplogs made up of wooden boards controlled manually or by winches, or by a screw and wheel arrangement • Needles made of dimension timbers • Rap gates with or without counterweights and floats • Sliding, fixed-wheel, or stoney vertical-lift gates • Bear-trap gates • Needle, tube, fixed-cone, hollow-jet, sleeve-type, butterfly, and sphere valves for pipe intakes Additional information on different types of gates and valves is given in [Davis and Sorensen, 1970: chs. 21 and 22; and ASCE/EPRI, 1989]. The design of gates and valves should be fmalized after consultations with mechanical engineers and manufacturers, par- ticularly for mechanically-operated, remote control, and automatic gates and valves. In some states, the Department of Fish and Game requires that the inlet gates or valve have an automatic closure feature in the event of penstock rupture. Depending on the layout and design of the intake and diversion structures, one or all of the following types of gates may be required: • A gate at the inlet to the pipeline or canal. The type of gate or valve used for intake closure will depend on the size and location of the gate or valve. The device must be capable of operating with maximum potential flow through the system. This maxi- mum flow must consider the possibility of ruptured penstocks when they are part of the system or at least a full load flow through the generating unit. If the gate or valve is located at the head of the penstock, the arrangement must include provision for the release of air during penstock filling and air admission when emptying. • A gate to drain the area behind the trashrack and fishscreen located upstream of the trashrack. • A gate located within the intake structure to allow for flushing of sediment. This gate can be used as a drain and can also be opened during high flows thus reducing the number of times the structure is inundated. Because of the high erosive potential of sediment and rocks passing through this gate, the seats of the gate should be made of steel. Concrete seats tend to get eroded and pitted, resulting in the development of leaks around the gate. The coefficient of head loss through gates and valves may be calculated by the follow- ing formula [Davis and Sorensen, 1970: ch. 22]: where cd = free-discharge coefficient Gates and valves Types of gates 2-19 ASCE/EPRI Guides 1989 Free discharge coefficients Power canals Sizing Permissible velocities and side slopes Approximate values of the free-discharge coefficient, Cd are given in table 2-4. Table 2-4. -Free-discharge coefficients for gates and valves. Type of gate or valve cd Slide gates 0.95-0.97 Needle valves 0.45-0.60 Tube valves 0.50-0.55 Fixed cone valves 0.85 Hollow-jet valves 0.70 Sleeve valves 0.85 Butterfly valves 0.60-0.80 Sphere valves 1.0 C. POWER CANALS 1. Sizing Guidelines for sizing power canals for small hydroelectric projects are the same as described in [ASCEIEPRI, 1989b]. Power canals for small hydroelectric plants may some- times be aligned along existing drainages or ditches, designed as contour channels, or exca- vated to minimize cut and fill. To minimize cost, they should be designed as unlined trape- zoidal channels with no rapids and drops. The earthen channels should be sized to pass the design discharge for the generating units with a minimum freeboard of 1 feet plus 25 per- cent of the design water depth. The maximum pennissible non-scouring channel velocities and sideslopes for these channels are shown in table 2-5. Table 2-S. -Permissible velocities and sideslopes for earthen power canals. Bed and bank material of the channel Ordinary finn loam and volcanic ash Colloidal stiff clay, noncolloidal graded loam to cobbles, and collidal alluvial silts Cobbles and shingles Permissible channel velocity, ft/s 2.5 -3.0 3.75-4.0 5.0 Recommended slide slopes 2H:1V 1.5H:1V 1.5H:1V In many situations, topographic constraints may require these channels to have steeper slopes producing higher flow velocities. In such cases, the channels may have to be lined or the bed slopes flattened by introducing drop structures at appropriate locations. ASCEIEPRI Guides 1989 2-20 2. Hydraulic Design Methods for the hydraulic design of lined and unlined earthen channels are documented in [Chow, 1959: ch. 7; Barfield et al., 1981: ch. 3; Davis and Sorensen, 1970: ch. 7]. The methods described use Manning's formula for uniform flow along with the continuity equation as follows: where, for a trapezoidal channel: Q = flow (ft3/s), v = flow velocity (fils) R = AlP= Hydraulic radius (feet), s = friction slope assumed to be equal to the bed slope of the channel for uniform flow (feet/foot), n = Manning's roughness coefficient. A = by+ zy2 =area of flow (ft2>, p = (b+2~)(Y) z = channel side slope, horizontal: vertical, b = bottom width of channel (feet), and y = water depth (feet). Typical values of Manning's roughness coefficient are shown in table 2-6. Table 2-6. -Typical Manning's roughness coefficients for channels. Channel material or type Oean, straight earthen channel Straight earthen channel with short grass Winding and sluggish earthen channel with some weeds Winding and sluggish earthen channel with cobble bottom and clean sides Unmaintained earthen channels with uncut weeds and brush on sides and clean bottom Concrete-lined channels Asphalt-lined channels Gunited channels Rubble masonry Riprap-lined channel Manning's n 0.022 0.027 0.030 0.040 0.050 0.013-0.017 0.013-0.016 0.019-0.022 0.020-0.025 0.030 Hydraulic design Manning's equation 2-21 ASCE!EPRI Guides 1989 Linings Common linings Appurtenant structures 3. Linings In certain situations, the topography along the channel aligmnent and cost of excavation may require that the channel be designed with a relatively steep bed slope resulting in high- er velocities of flow than the permissible nonscouring velocities for earthen channels. In these cases the channel bed and banks have to be lined with erosion-resistant material. In other situations, the available material along the bed and banks of the channel may be too pervious· resulting in significant seepage losses. In these cases, the channel bed and banks have to be lined with impermeable material. The cross-section of a channel lined with con- crete, asphalt, or synthetic membranes may be smaller and the permissible bed slope for a lined channel may be steeper than that of an unlined channel designed for the same dis- charge. Also, there may be differences in the operation and maintenance costs for lined and unlined channels. Therefore, it is desirable to make an economic evaluation of both lined and unlined channels before finalizing the design of the power canal [Davis and Sorensen, 1970: ch. 7]. Some commonly used canal linings are listed below: • Rock riprap -details of riprap design for erosion protection on the bed and banks of channels are given in [Simons and Senturk, 1977: ch. 7; Barfield et al., 1981: ch. 3, and COE, 1970]. • Vegetation protection against erosion [Barfield et al., 1981: ch. 3; Chow, 1959: ch. 7]. • Earth linings including clay liners, soil-cement lining, and use of soil sealants, stabi- lizers, and admixtures [Davis and Sorensen, 1970: ch. 7]. • Concrete and asphaltic linings including guniting [Davis and Sorensen, 1970; USBR. 1984]. • Plastic membranes, geotextile mats, and fabriform linings -detailed information on these types of linings should be obtained from manufacturers of plastic, geotextiles, fabricast concrete, and other synthetic materials. Information on the designs of flexi- ble buried linings of polyvinyl chloride (PVC) or polyethylene (PE) membranes and flexible exposed linings of butyl rubber (isobutylene-isoprene), EPDM (ethylene propylene diene monomer), hypalon (chlorosulfonated polyethylene), CPE (chlorinat- ed polyethylene), HDPE (high density polyethylene), and HDPEAM (high density polyethylene alloy membranes) is given in [USBR, 1984]. 4. Appurtenant Structures Appurtenant structures for power canals of small hydroelectric projects include the following: • Silt Ejector or Extractor. This structure is described in the section on Sediment Control. • Drop Structures. These structures may be used to reduce the bed slope of the power canal so as to minimize the requirements for linings and erosion protection measures. The methods for the design of these structure are given in the Design of Small Canal Structures [USBR, 1978: ch. 2]. ASCE/EPRI Guides 1989 2-22 • Cross-Drainage Structures. These include inverted siphons, over chutes, drain inlets, culverts and bridges. The methods for the designs of these structures are given in [USBR, 1978: ch. 2; AISI, 1971; BPR, January, 1963; and DOT, 1973]. • Escape Channels, Wasteways and Side Channel Spillways. These are gate con- trolled or uncontrolled outlets located in one of the banks of a power canal connected to a natural drainage by a manmade or natural channel. The objective is to permit safe release of surger resulting from a sudden shutdown of the generating units. The meth- ods for the design of these structures are given in Design of Small Canal Structures [USBR, 1978: ch. 4]. As an alternative to these structures, surges in power canals may be taken care of by providing additional freeboard in the canal above its full sup- ply level [USBR, 1978: ch. 1 ]. D. PENSTOCKS AND CONDUITS 1. Types and Materials In general, all the types and materials of penstocks used in Conventional Hydro practice are suitable for small hydroelectric installations [ASCE/EPRI, 1989b]. Depending on topography, site geology, cost of excavation, ambient temperature, environmental consider- ations, and size and length of the conduits, penstocks for small hydroelectric plants may be designed as surface or buried pressure pipes. The selection of the material of the penstock for a small hydroelectric plant is based on the cost of the conduit, transportation, installation, working pressures, corrosion resistance or durability, and range of sizes in which the pipes are readily available. Information on pres- sure pipes suitable for small hydro is given by Gordon and Murray [1985], Giroud and Frobel [WPDC, 1984], and AWWA Manual M9 [1979]. The basic characteristics of some of the pressure pipes which may be used for small hydro- electric installations are summarized in table 2-7. 2. Hydraulic Design a. Steady-State. -( 1) General. -Low-head hydro by its very nature requires short waterways and reasonably efficient operation. A loss of 10 feet of head for a 500-foot hydroplant has little impact compared with the loss of 10 feet of head from a plant having a gross head of only 40 feet. (2) Friction Losses.-Shear stresses at the boundaries are the source of friction losses in hydraulic conduits. The guidelines committee suggests that the Darcy formulation be adopted by hydro engineers for all computations. The Manning formula appears to be so deeply ingrained in the hydraulic literature its usage is difficult to discourage and therefore its use is acceptable for open channel flow. The use of Scobey, Chezy, Hazen-Williams and other such formulae is discouraged. Excellent graphs and designs aids are available in the literature [Hydraulic Research, 1983] for solving friction loss problems directly. A useful design aid is included on figure 2-13. Penstocks and conduits Materials Hydraulic design 2-23 ASCE/EPRI Guides 1989 Table l-7.-Characteristics of selected pressure pipes. Approx. Max. nu Size max. working (soU unit range, pressure wt = 110 Average Type of pipe feet (ft of water) lb/ft3) Mannlng'sn Comments Reinforce concrete 1 to 12 150 40 0.013 Requires interior Characteristics (precast) steel jacket to of prevent leaks pressure Cast-in-place Ito 20 58 300 0.014 Requires interior pipes concrete steel jacket Prestressed 2 to20 460 200 0.013 Requires interior concrete steel jacket Steel 1 to 8 4600 20 0.012 Watertight, requires occasional painting Asbestos cement lto3 580 30 0.011 Brittle Polyethylene•• 1to4 460 15 0.009 Watertight, light (Plastic) weight Polyvinyl chloride 1to2 300 15 0.009 Corrosion resistant, (PVC) subject to degradation by ultraviolet light Fiberglass epoxy lto2 800 15 0.009 Light weight and reinforced PVC corrosion resistant Fiberglass re-lto4 515 30 0.01 Light weight, enforced plastic corrosion resistant mortar ••• Wood stave 3 to 18 400 10 0.012 Requires spray coat with (pressure creosoted tar every 5 years and or steel-banded) a valve at downstream end to prevent dry out during turbine maintenance Thermoplastic 1to2 460 15 0.009 Resistant to ultra- violet light, less brittle than PVC pipe Ductile iron 1to2 200 20 0.015 Subject to pining and corrosion; protective coating or sleeving is required *Tile infonnation in this table is approximate and must be checked with manufacturers or suppliers . .. High density polyethylene (HOPE) pipes have high resistance to ultraviolet light degradation. ••• Also available as glass reinforced plastic pipe (GRP), fiberglass-reinforced plastic or polyester (FRP), glass-reinforced epoxy (GRE), or fiber-reinforced plastic mortar (FRPM) pipe. ASCEIEPRI Guides 1988 2-24 Hydroelectric engineers deal regularly with a vast array of hydraulic conditions from smooth plastic pipe to unlined rock tunnels. 1be physical features they study range from the free-surface high-velocity flows of a spillway to the flow in a smooth closed conduit transition. All of the friction data pertaining to these different flow regimes can be correlat- ed and unified through the roughness factor, Reynolds number and the Moody diagram. To convert a given Manning n value to the Darcy fvalue use the equation below. Din the for- mula is the hydraulic radius for a circular pipe. f _ 185 n2 -1/2 D Analytic formulae that give the Darcy fvalue (Colebrook-White) are difficult to use. The following formula provides adequate engineering accuracy [Miller, 1982]. I= 0.25 [ k 5. 74 ] 2 where: k = roughness (mm), D = diameter (meters), and Re = Reynolds number. loge 3.70 + R~.9 (a) Roughness values. -The difficulty in calculating friction losses is due to the uncertainty in selecting a value of pipe roughness. Suggested roughness values are given below. An allowance must be added to new pipe values to account for deterioration in service brought about by surface deposits, crossion, corrosion, bacterial slimes and growths and marine and fresh water fouling. Experience of similar systems is the best guide to selecting roughness values and deterioration allowances. Table 2-8 presents some useful pipe roughness values. (3) Form Losses. -These losses result from the nonsymmetrical pressure distribution caused by flow around an object and are the other major source of energy losses in hydro- electric conduits. The losses relate to changing shapes presented to the flow, i.e., expan- sions, contractions, transitions, entrances, and bends. For low-head plants form losses are likely to be the major losses, while in high head plants having lengthy conduits the friction- al losses can be expected to be more important. Form losses can also be the cause of vibra- tion, cavitation and other undesirable hydraulic effects. Form losses are usually presented as a coefficient (K) times the velocity head. The defining formula is: v2 H =K-L 2g Entrance loss: K = 0.50 for a square-edged entrance. Even minor streamlining of the entrance dramatically reduces the loss. Formula for the Darcy/ Roughness values Form losses 2-25 ASCEIEPRI Guides 1989 ~ ® (l) ~>@® ® 0 ® n h Pivot v• tr1 ..J.. line 29 V VO R<ss· Q D e e/0 ~ PJ P£ R£SISTANC£ DIAGRAM l IS JO zoo ~!sgpm ~~:;;t ~ afler the Manual of British Waler Supply Practice •OQ 10 •o' :: 6 8 too 1 Boundarv ~ '0 , .. : 1 2o 110 ' so Molena/ ti) jOI <~' riO• Ill 200 60 / \ . . / " -/ ' ~-w \0 Q) 40 / \ ,..,tul I'"P< oo I ~ \ \0 NIO ;; '10\ f 40 I 1/ \ Rriatlvt .....,_,. atO loO 10 to ;I' \ 10 , .N,-1 --.<CTI"TI .... i-ol-rt-rt-r.-rl--.lr-Ti""ll"":.-rl-,.1-irTITirl-rl-oi,..,..IMii <0 I : /' IO. 104 to \\ ~~ l-1o·l / n,.,,*"" ,,.,,,-{ j_ ·• I 1 ;I' IO '•o \ •• 6 / f 6 Ct;~ncr'l• 20 / • ~~ -·v I: .04 4 Ca.t irun ~ t: 11 ~ ~ ----.1. = 10 /-4 •o' 10 •o·• •• • • • ., ......:~::!..-.~ r / ~ I"' ~~··· I -8 / l l 9 \ : =:t ~ ~l a .: • , ~ v -~ . , • l .LI 004 6 / l -' 1 -A•pha!f.oJ \ ! 5 . • ~;!:~'\--J...L -1--1-rt ;;: / :t: E ~ ~ 1 <•"''"'" \ ~ l .:: ....,-001 5I / .E ot "' .,_ •' '-\ IIi -1---~~ ..... ~~··');ltl Jl 4!! / ]. ::; ::: ~-i ·I 1 "i ro ... o2 :" __ oo• ;1:: / I ll ~ 10 1 ~ 10 ~ N ., --~rl ~ ·:..".· 00011 / "' ' 2 l o '-0 5 ... 1 ! I :=r--ti~ ~"S ·· ' :; · , = E / ::: ~ > o.a ' •o' .. ,0 • N J :-.....;._r.. ' ~ ..-~.}..:LF._..,.-...1.-f" 2 .1" / ~ l Oi 1_ "' 1 .: -·--~~ :,.-r ,....... / >. 4 .£. 'il Zl . ~ • ~ ~~ I • '""' 1 / Q4 i . ' I ~~' ' '.I-' i. ,If ~ 91:-lo' 0 ·,,,, 1!1~~-... -:-!. / -.~1 ! I I-I 'II i . ; '-.."l.f r--:-...-,1 !:... -o-"', / J0 ----r~--~-~-f -J ·~ ..........__ I I .1).)()0~ O., ........ / f 0.1 o.t i 1-lo I· ~ t ~o<i• 04 .01 01 10• -:r.: 1-z u.1 @I I I Ill I I Ill I I ! IIJ ! I Ill I till~..... e a1 u • 10 • 9 10 1 10. 161 10° ..,. wfP'P< ' .01 • ~~/ M R11 v ; oz .06 @> 1 • t•t•rm• • 1•a•nm1 'l'l'l'llltl ti • rn• 1 1 tiiiM 4 os •.• ••' • .. ' .: r .04 VD VOonll'l .. c /J, ... ,.,,._•Ho.4A t. ~~ 0.4 11' !' t....,-• L.,• I 008 1 · z n I ·• oe 0~6 QJ .lit 10 / Air ••••p.natun '" •r * o..1 \Val•r l•tn"ml~r• in •f / al ,.,.., ptUiilf"f .OOt J -JOO i'OII 100 Ill; ~f44JI Jlll> t>IJ lJIIt<Jl IO Oi ® .. ,. ··•''1'"1 'l'~f•',,l·,} l 'I 'l'T'l''l' ·~ • or .Qf ·• 0.5 v ~ Kirt•.,.otic: vi•co•it, rill ff/uc f.,.t.Kiuillituf(/,(/Jq.,fKiJipiptl r1f#'r 111 m-.:mu'-'At'"S S/l«lfil:llliHJt Figure 2-13.-Diagram for determining the Darcy friction coefficient. Table 2-8. -Pipe roughness values, k (in millimeters). 1. Smooth pipes* Drawn brass, copper, allumium, etc. 0.0025 Glass, plastic, perspex, fiberglass, etc. 0.0025 2. Steel pipes New smooth pipes 0.025 Centrifugally applied enamels 0.025 Light rust 0.25 Heavy brush ashphalts, enamels and tars 0.5 Water mains with general tuberculations 1.2 3. Concrete pipes New, unusually smooth concrete with smooth joints 0.025 Steel forms first-class workmanship with smooth joints 0.025 New or fairly new, smooth concrete and joints 0.1 Steel forms average workmanship smooth joints 0.1 Wood-floated or brushed surface in good condition with good joints 0.25 Eroded by sharp material in transit, marlc.s visible from wood forms 0.5 Precast pipes, good surface finish, average joints 0.25 4. Other pipes Sheet metal ducts with smooth joints 0.0025 Galvanised metals, normal finish 0.15 Galvanised metals, smooth finish 0.025 Cast iron, uncoated and coated 0.15 Asbestos cement 0.025 Flexible straight rubber pi,r: with a smooth bore 0.025 Corrugated plastic pipes • (apparent roughness) 3.5 Mature foul sewers 3.0 Wood stave 0.6 • Extruded, cast and pipes formed on mandrels may have inperfections that can increase roughness by a factor of 10. •• Commercial corrugated plastic pipes in the 40-to 100-mm diameter size range have corrugation crest length to depth ratios of about 1.5. Increasing the crest length to depth ratio from 1.5 to 5 may double the friction coefficient. Transition loss: K = 0.05 to 0.08 in a well-designed transition, where the velocity is kept constant from the rectangular to the circular section. Expansion loss: The expansion losses for sudden and conical expansion are shown on fig- ures 2-14 and 2-15, respectively. The defining formulae are also shown on these figures. Pipe roughness values 2-27 ASCE/EPRI Guides 1989 Loss at expansion Loss at contraction l.D III'VIi~! I i ' I I I ! :)~-l.S ill ' ' ' -! '111 .KI. I i I I I I ' I ' I I 1/ / I I ~.-3 ! I I ' I ! I I l I I I I Y/1 I I I I I I I I I I I I I I If I I I ~~~ I 'UI i I I + I I I I I I i I I , I K I I I I I I ' v.-v,-IY I I I I I I li,•K'v,;vt 11 I I I I I f I I I I I I ! ! .. I I I ! I i I i I : ' F ' Figure 2-14.-Loss at sudden expansion. Figure 2-15.-Loss at conical expansion. Precautions against deterioration in seiVice are: 1. Good initial surface finish to minimise areas of low velocity where deposits can begin to form in the wakes caused by roughness. 2. Adequate protection against corrosion and erosion. The contraction loss equation is given by the expression: where v2 is the velocity in the small pipe. Variations of contraction coefficient with area ratio. 0.1 0.624 0.2 0.632 0.4 0.659 0.6 0.712 1 0.8 0.813 Figure 2-16.-Loss at sudden contraction. 1.0 1.0 ASCE/EPRI Guides 1989 2-28 Venturi and orifice loss: The head loss coefficient of a well designed venturi meter varies from K = 0.02 at large diameters (60 in x 30 in) and high Reynolds numbers to K = 0.10 at small diameters (4 in x 2 in) and low Reynolds numbers. The head-loss coefficient refers to velocity head at the throat section. Orifice head loss: The head-loss coefficient K for flow through an orifice plate in the pipe at high Reynolds numbers (Re > lOS) depends only on the orifice to pipe area ratio. The values of K, determinedby Weisbach, can be interpolated from the table below: Loss through an orifice plate. 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 K 226 47.8 17.51 7.80 3.75 1.80 0.80 0.29 0.06 0.00 Branch losses depend on: a. Direction of flow which may be dividing or combining b. Percent of flow diverted to or received from a branch c. Branching angle d. Area relationships of branches to the inlet pipe e. Length of the conical transition and angle of taper of the branch For additional data on branch head losses refer to volume 2 of the Guidelines. Additional features, such as tie rods, splitter plates, filler blocks, etc., increase the possible variations to an extent that precludes systematic experimentation. Studies indicate that, in symmetrical flow conditions, the head loss in a wye for an angle of bifurcation not over 60° is not more than 6 percent of the velocity head. Tie rods greatly increase the head loss. Loss through orifice plate Bend loss: The head loss in a bend depends on the relative radius RtJD of the band, the Bend angle of the bend, the Reynolds number Re, and the relative roughness E/D of the pipe at loss the bend. This partly explains, why seemingly similar experiments carried out by various investigators give vastly different results. In addition, there is not enough evidence in many cases to conclude that the true local loss has been reported. Average values of the probable loss coefficient Kin terms of R,jD, adjusted for large pipes are shown for a 90° bend. Variations of loss coefficient with R,jD. RiJD K 0.8 0.3 1.5 0.18 2.0 0.13 Valve loss: Head loss through a valve depends on: a. Type of valve b. Design c. Ratio of valve diameter to pipe diameter d. Valve position (% of opening) 3.0 0.1 2-29 4.0 0.08 5.o+ 0.08 ASCE/EPRI Guides 1989 Valve discharge equation Intake losses Hydraulic computations Valve loss is calculated from the expression: v2 h =K-L 2g in which v = average velocity in the pipe. The discharge through the valve is: Q = CA.Jliii where: C = the valve discharge coefficient, A = the area based on the nominal valve diameter, and H = the head differential across the valve. The head-loss coefficient K and the discharge coefficient C are related by the expression: K=-1--1 c2 Valve manufacturers usually give the valve discharge coefficient in USGPM for various valve positions for 1 lb/in2 pressure differential. Intake losses: Figure 2-17 shows representative cases of the Corps of Engineers intake structures. The losses include the trashrack, entrance, gate slot, transition, and wall friction over the entrance distance. For low-head plants with very short waterways problems occur in applying any hydraulic fonnulae. The coefficients are usually based on assumptions about the development of the velocity distribution and for such short conduits conditions applying to the coefficients may not be met. This has further implications for the hydraulic engineer who must design conduits that present good flow conditoins at both the entrance and exit to the turbine. this important subject is discussed in, [Fisher, 1987] (4) Hydraulic Computations.-A primary interest in hydraulic calculations is to compute the hydraulic effects of the conduit (energy losses) on the plant operation. The net head across the turbine, flow available to the turbine and as a result the power output of the tur- bine is dependent on the reservoir water surfaces and the waterways losses. Ordinarily the engineer seeks to plot a turbine characteristic curve, which gives the head flow conditions for various gate opening of the turbine against the system (hydraulic) characteristic curve. The system curve is merely a plot of the head losses in the system. The total system loss Hv is the sum of the system losses. It is usually represented by: H L = Losses (trashrack + intake + reducers + expansions + bends + friction + valves + tail- race+ exit) v 2 v 2 v 2 v2 v 2 v 2 v 2 v 2 v 2 HL =K -+ K -+ K-+K-+K -+ K -+K -+ K-+ K t 2 g in 2g r 2 g e 2 g b 2g f 2g v 2g t 2g u 2g ASCE/EPRI Guides 1989 2-30 CONOUIT 1'100"!:11 ~ 11bNOtbs vtLOCih AYI:IIIAOC INTAKE COI:P'P'IQENT K SHAI'I: OiAWlZ) NUWUJII (2) HI:AO (1) ll) C*CM&IONS .. ~TOT""' PUT. SINGI..[ INTAIC[ (CONCJIIETE 0A1o1 CONDUITS) CZ tOUIVAC...EfrrfT OIA .... Tt• ro-NQirleC~ 'c ':a ~ ,.. 1.1• u • 111 1 .,_ .. a.• IICTIONS eA&CD ON MYa-...... .c ~ l» OOC.a NOT llliiiCI,.UQC. ~;A1't.-M..QT UlUC.I WI t..l.MGTN fW T.A,.. .. TIQIIII !PliO TOT~ C__,1'0T'T""':) (SI ~ CJ.IINC ~ A.I.IS MOt'IZDNTAI. --lc----! ( PIIOP'IL.t l' '" ~------- ( PL. AN ,_r~t~._ A•40, I•J.O C....O.I•Y ··~Co-t.f ~ n·zo-.J A• f !1. l•l..S C•tO.O. t•~-1 '•<&.l .. G•t ... u t.7 .. ..,. (WOO(U OOUIIL.[ INTAKE (lAJIITM OAiol T~ltL.) ~ .... t.l a r .. {Pti01'0.....V 1"0~1 A•IU.I•JIO C•teO.O•&O C• U,T•t.J..O 0.07 Ql o.• :o~ •• ....... .,. II•N 0.11 "IIOP'IL.[ :[ ¢ -:=::Ho -~ :o "L.AN I'IIIOP'IL.E ~ ' ---0 ·= = ~ PL. AN G ; Zi IIIIODCU -.u (IU......cl rr ,. .. tQ!:~J.~ 31 0.7•tSXIO" ••-72 ~ -~~ a•a•a. I• ... o C:•I1G. D•UJI £•tt.o. T••ao rr JtAtQ!I.'-,. Ot•t.O a tO• ..... o.u.-.u 1-u csa..-CJ TIIII,.L.[ INTAKE (tAlliTH OAW TUNNEL.) Q'll~ A•JOO. I•UO C• .. .0. O•tiO ,. '~· , .... o .. tNT A!C£ !:S AQ LMJ " .. ii W•VI:LOOn .. C0fr0.11' -· ·-· Figure 2-17.-Intake losses. [Ruus, 1980]. where the appropriate velocity is used in each fonnula. Usually the appropriate velocity is the average velocity as given by v = QJA. The head available to the turbine is then the head differential between the water surfaces minus H L· Typically hydro systems involve pipes in series, in which case the computations are straightforward. In other cases plants may have branching and parallel conduits. These sys- tems have no differences in their hydraulics, however, in order to obtain a solution the hydraulic equivalent of Kirchoff's laws is needed. Such solutions are explained in any hydraulics text or handbook. The parallel and branching conduit solutions can become tedious and a computer becomes a practical necessity. Turbines fed from two reservoirs are an example of a branching system, while multiple tur- bines on a manifold with a single upstream and downstream conduit are an example of a parallel hydraulic system. Electrical circuit analogy is useful to establish the equations, however losses are nonlinear and matrix analysis is therefore not effective for obtaining a solution. Intake losses Series branching, parallel conduits 2-31 ASCEIEPRI Guides 1989 Transient analysis Definition sketch b. Transient Analysis. -( 1) General -No technical differences are noted between tran- sients in small-scale hydroplants and those described in the Conventional Hydro Guidelines. Small hydro installations by their very nature are likely to have the following characteristics: low-head, short waterways, run-of-river, nonstorage, additions to existing projects, base load, limited in governing capability, minimal cost installations, or located on canals. All of these tend to minimize the importance of waterhammer calculations in the plant and system design. • Turbine model testing usually addresses only efficiency and other steady state operat- ing characteristics. Obtaining the complete four quadrant characteristic for extensive waterhamrner analysis is usually not necessary or cost effective. • Available charts, graphical analysis, numerical (hand) computations, can be useful tools in the analysis of small hydro plants, without recourse to extensive analytical studies. • The same considerations that govern waterhammer in large plants apply to waterham- mer in small plants. Long waterways and rapid flow variations produce undesirable pressure effects. The definition sketch, (fig. 2-18), defines the elements of a hydroelectric scheme that affect the transient analysis. For small hydro analysis most of the features shown are need- ed for analysis. The usual small hydro project that has been developed to date in the United States is likely to feature a run of the river intake a small reservoir with pondage, short waterways, no surge tank, no significant tailrace, and discharge to a river or stream. If a surge tank is required it must be included in the analysis. [Chaudry, 1986] gives an excel- lent and useful summary of transients in hydropower plants. Figure 2-18.-Definition sketch for hydraulic transient analysis. [Chaudry, 1979]. ASCEIEPRI Guides 1989 2-32 (2) Waterhammer Studies.-Waterhammer studies address two design issues: a. The impact of the hydroplant operation (valves and turbines) on the design of the conduit b. The impact of the water column inertia on the operation of the turt:>ines Design considerations under item (a) above lead to establishing the maximum and mini- mum design gradients. These computations are always necessary as part of standard design procedure, as are consideration of all transient operation such as plant starting and stop- ping, filling and emptying the conduit, load acceptance and rejection, draft tube waterham- mer, surge tank design, valve operation, and runaway speed. Item (b) relates to plant governing and the impact of the quality of the plant's operation in the electrical system. Practical considerations indicate that good governing is not usually essential in small hydro plants in the United States. The plants are connected to a large grid where their small relative capacity does not greatly influence the overall operation. Furthennore, the costs associated with designing for good governing may be excessive com- pared with the benefits. For instance, a recent OOEIEPRI publication [EPRI 1986] reported only 1 percent of the 250 small-scale hydroplants studied had black start capability. (3) Small-Scale Hydro Technology. -Small-scale hydro deals with the development of low head hydro sites that up until the oil embargo were not considered economically feasi- ble to develop even though the dam and associated features already existed. Transients in these plants therefore relate mostly to sites that utilize the new generation of low head machines that have been developed for this purpose along with the usual Kaplan, propeller, and bulb units already in use. ( 4) Transient Studies. -Transient studies usually address the following: • The maximum and minimum hydraulic grade lines • The need for surge tank • Valve closure movements, wicket gate closure • Tailrace conditions • Governing needs o Pressure regulators o Runaway speed • Startup and shutdown procedures (5) Comments.-It is basic to water-hammer that it deals with the problems caused by the momentum effects of the long water column that supplies flow to the turt:>ine. Inertial effects relate directly to the length of the water column and usually their severity is directly proportional to the length of the conduit. It follows that on a typical low head plant where the conduit is only a few hundred feet long that even rapid movements of a control valve will not lead to excessive waterhammer. Conversely low-head plants designed for the usual factors of safety cannot tolerate large overpressures. The following calculation is offered as a guide. Consider a plant with a pen- stock 800 feet long and having a wave velocity of 3,220 ft/s. The round-trip wave travel Water hammer studies Transient studies 2-33 ASCEIEPRI Guides 1989 Surge tanks time is 0.5 second. Then if the velocity in the penstock at the turbine is reduced 1 ft/s every 1/2 second, the waterhammer at the turbine as given by the Joukovsky formula: a 3,220 L1h = g L1v = 32. 2 ( 0. 5) = 50 ft which may be considered excessive in a plant that has an operating head of only 50 feet. This simple but exact computation indicates that if waterhammer is a problem in a low head plant is may be difficult to deal with. "Small" hydroplants having capacities of 10 to 15 MW can play a useful operating role in the power system if they can produce peaking energy or contribute to stable system opera- tion. It is suggested this be examined because of the unique operational advantages hydro offers and since limited hydro development is available. (6) Surge Tanks.-The fundamental action of a surge tank, is to reduce the length of the column of water by placing a free water surface closer to the turt>ines. The statement is just as true if the surge tank is on the tailrace though it would be unusual to fmd a surge tank on a small hydro tailrace. Such tanks are necessary if waterhammer pressures are excessive or if stable governing is required. The water in the tank surges up on load rejection and down when the turt>ine accepts load. Useful graphs that can be used to determine the surging are presented [ASCE/EPRI, 1989; Parmakian, 1965]. Typically some manner of throttling is introduced at the base of the tank since this can greatly reduce the surge amplitude as well as rapidly attenuate the surging. The throttling introduced has an appropriate value such that it does not increase the conduit design pressure. MAXIMUM UPSURGE _L_--+-+ STEADY STATE OPERATING GRADIENT STATIC GRADE LINE ~---------------+-~ ~---------------------+~~ MAXIMUM DOWNS URGE TUNNEL Q 0 = INITIAL FLOW A = TUNNEL AREA L = TUNNEL LENGTH F s S=~ fFLSinJAg(t) F VA'Q FL ORIFICE \\ Lp = PENSTOCK LENGTH Ap= PENSTOCK AREA TO POWERHOUSE DAMPING Figure 2-19.-Surge tank definition diagram. ASCE/EPRI Guides 1989 2-34 For a simple surge tank, the maximum surge in the tank (Sma;x) can be computed from the formula: and its period (7) from: where: T = surge tank period (s), s = Q() fiiL max F ..JAg {jiL T = 2 1C -J --;;i;g Sma:x = maximum watersurface rise above operating level (feet), Q0 = initial flow (ft3Js), F = surge tank area (ft2), L = length of waterway between the reservoir and the surge tank (feet), A = waterway area (ft2), and g = gravity constant (ft!s2). Typically surge tank throttling will reduce the surge amplitude by 20 to 30 percent with similar improvement in the damping. If a surge tank is needed the conventional hydro guideline should be consulted [ASCEIEPRI, 1989]. Surge tanks are treated in greater detail there. (7) Runaway-Speed Computations.-Small hydroplants are usually low head and as a result high runaway speeds are evident. They do not however generate a head rise since throttling due to the turbine overspeed does not occur. Funhennore, the very short water- ways limits speed increases due to waterhammer. If a turbine model test is available, the runaway speed will be krK>wn from those tests. A waterhammer allowance must also be included. This can increase the runaway speed about 10 percent for Francis turbines. The runaway speed of the turbine may be reached before the wicket gates close. In such a case the speed is related to the turbine type, Ns, and the waterhammer will be a function of the flow extinguished as the turbine approaches runaway. [Pannakian, 1985] indicates the flow as the unit reaches runaway is given by the expression: where: Q0 = the initial flow (ft3Js), QR = the flow as the unit reaches runaway speed (ft3Js), and Ns = specific speed in English units (ft/min). Note that at Ns = 70, QR = 0. Maximum surge Runaway speed 2-35 ASCEJEPRI Guides 1989 Pressure regulators Canals Runaway-speed calculations are ordinarily made assuming the turbine control valves do not operate during the transient. All parts of the turbine-generator are designed for this mode of operation. The turbine control valve must be designed to close against full run- away flow conditions. (8) Pressure Regulators.-In instances when the closure time of the turbine valves must be rapid a pressure regulator may be necessary. The usual circumstance is to place a valve in parallel with the turbine such that it opens as the turbine wicket gates close. This has the effect of slowing down the flow changes in the penstock, figure 2-18. The bypass valve then closes at a much slower rate. Computations are easily handled using the graphical analysis and the general waterhammer diagram [ASCE/EPRI, 1989; Pannakian, 1955]. contains numerous examples of typical waterhammer problems useful for engineers of small hydro. The graphical technique as explained in his text is an alternative to computer solutions. 1.0 0.8 ._, ~ Control late-~ Relief valve-, Uniform closure in 60 seconds-' Combined movement I ---I , I ~ I --I ' ' -... ~-' --::::.. ::::---....... l 0.6 "0.4 0.2 0 0 _...::L -----::..:::::..-. 2 3 4 5 6 TIME IN SECONDS Figure 2-20. -Relief valve operation at power plant. [Parmakian, 1955]. In many instances small hydro plants are added to the outlet works of existing dams. These outlets usually have a minimum overpressure allowance since they are designed for a valve to control flow with long closures. In such instances where the turbine discharge cannot be controlled to meet the required flow changes a bypass valve may prove to be a reasonable solution. The pressure regulator does not operate during load acceptance. (9) Canals. -Small hydro plants located on canals should experience little waterhammer since only a short closed conduit water column is involved. The flow variations occur in the canal as surges and provision for containing the surges during load rejection is neces- ASCE/EPRI Guides 1989 2-36 sary. Pressure variations due to hydro plant operation are not a problem. The canal must also provide flow during load acceptance. A number of small hydro plants have been installed at canals. The special problems associ- ated with these plants can be determined by study of the individual plants. ( 10) Governing.-Power system stability relates to the problem of maintaining syn- chronous operation of the generators and motors (constant frequency). Every machine in the system should have the capability to rapidly adjust to changing loads. When such con- ditions do not exist the hydro plant "borrows" from the system to make the changes in a stable manner. The subject is usually called regulation, load following, governing stability, or frequency regulation and is of great importance to power system engineers. The waterways geometry of hydro projects are ordinarily established based on an econom- ic diameter analysis given by the steady state conditions. Typically waterhammer analysis is conducted based on that geometry. Attention to the regulating characteristics of the unit should also be addressed at this time since subsequent changes are usually different with- out a large economic penalty. The regulating characteristics of a unit are a function of the unit's mechanical inertia or flywheel effect, the inertia of the penstock water column and the characteristics of the tur- bine. The flywheel effect is a stabilizing influence while the water column is a destabiliz- ing influence on governing. In some instances the waterways can be sized to give reasonably good water starting time for an incremental one unit start-up and thereby assure that the minimum stability index as measured by the ratio of mechanical starting time to water starting time (T ,//' w) will be economically obtained. The inertial effect of the water column is approximated by: T _LV w-tf T w is defmed as "water starting time." It is a measure of the time to accelerate the water column from zero velocity to some other velocity, V, at constant head, H. H = gross head across the turbine (feet), L = length of water column (feet), V = velocity (fVs), and g = gravitational constant (32.2 ft/s2). T m is defmed as the "mechanical starting time." It is a measure of the time required to accelerate the unit from zero rotational speed to the operating speed. Governing T,. 2-37 ASCE/EPRI Guides 1989 Considerations Adding WR2 WR2 is the rotating inertia of the unit and can be approximated from the following expres- sions. It is the weight of the rotating pans times the square of the radius of gyration. n = rotational speed of the unit (rpm), and hp = turbine full gate capacity horsepower. The ratio T ,/1' w• which is the ratio of the mechanical inertia (the stabilizing influence) to the hydraulic inertia (the destabilizing influence), is an important measure of the unit's ability to provide stable governing, to follow load changes, and to contribute to system speed regulation, and stability. Modem governors with electronic circuits cannot improve the quality of the frequency reg- ulation if the design of the hydraulic conduit system is deficient or the inertia of the rotat- ing masses is inadequate. When a unit is expected to follow load and provide frequency regulation and is operating isolated or is expected to operate as an isolated plant during emergency conditions, or will operate in a small system where the WR2 of the unit is ~45 percent of the total WR2 or rotating inertia of the system, the index of the unit should be ~5. Realistic water starting times, Tw, for a single unit start-up are on the order of 1 to 2 sec- onds. A water starting time exceeding 2.5 seconds will usually require an adjustment in hydraulic conduit dimensions [Moore, 1988]. When water starting times are ~.5 seconds, the required stability index ratio can usually be obtained by providing more WR2 than the amount nonnally provided by the generator manufacturers. Additional WR2 can be obtained for generators of less than 3 MVA by installing a flywheel between the generator and the turbine, where the unit is mounted horizontally. Additional WR2 up to 100 percent or even 200 percent of that provided by the generator can be obtained from a flywheel. Beyond that, some consideration should be given to increasing the diameter of the penstock to obtain the required stability index. Under certain circum- stances it may be convenient to consider a surge tank. However, in general, a small hydro scheme with units under 1,000 kW and a relatively short penstock cannot incorporate a surge tank economically. It is much more economical to consider providing additional WR2, increasing the penstock diameter, or rewoddng the project layout to shorten the over- all length of the water conductors. An attempt should always be made to make layouts as compact as possible. In units larger than 3 MW, additional WR2 can be built into the generator rotor. Each 10 percent additional WR2 added increases the generator cost by about 1 percent. Nonnally this is limited to 100 percent additional WR2. In extreme cases, this may be increased. In projects with large units, an increase in generator WR2 is usually the most economical way to obtain the desirable stability index ratio. The increased generator WR2 can also favor- ably affect the waterhammer and runaway speed. ASCEJEPRI Guides 1989 2-38 There is a limitation on the use of increased WR2 to obtain the desired stability when the water starting time, T w• is large. The promptness with which the system acts to dampen the frequency variation diminishes and a longer recovery time is required. ( 11) Waterhammer Computation. -Waterhammer pressures are a function only of the pen- stock characteristic the control device hydraulic characteristic, and its closure time history. When the valve closure is uniform, waterhammer pressures can be depicted on a graph (fig. 2-21). Note that for any closure interval less than 2L/a the limiting water hammer is reached at the valve and that value is given by the Joukovsky formula, &l = a/gtlv, cannot be exceeded. Furthermore as the closure time increases the graph will give more accurate results. The greatest inaccuracy comes from the valve closure curve not being linear. In general: where: aV0 --= p, the pipeline characteristic. 2gH0 = N, the number of round-trip, 2Ua, wave travel times in the valve closure time, Tc. As an example: a = 3,220 ft/s, V0 = 15 ft/s, H 0 = 500 feet, Tc = 4 seconds, and L = 3,220 feet then: /i& [ 3, 220 X 15 4 J r-aV0 H0 =f 2 X 32.2 X 500; 2 X 3,220 =/ l2gH0 3,220 k = 0.39 (from fig. 2-21), h = HIH0 = I+ 2(1.5)(0.39) = 2.17 x 500 = 1,085 feet measured at the valve, and H = H 0 + tl/1: the static head plus waterhammer. Figure 2-21 deserves study because it clearly shows the dependency of waterharnmer on the system variables and the rate of valve movement The chart has value for preliminary studies, but seldom are valve movements uniform. For design purposes, elastic solutions using the actual valve closure characteristics are necessary. Figure 2-22 presents a graph for determining the waterhammer at valve opening. In this case the pressure is measured below the hydraulic operating grade line. Water hammer calculations Example problem 2-39 ASCE!EPRI Guides 1989 I \ 1\ \ VALVES OF TIME CONSTANT H = ;[ 1\ \ 10 .08 .06 .05 .04 .03 .02 .01 VAl.UES OF K Figure 2-21.-Waterhammer chart for uniform valve closure. [Parmakian, 19SS]. t T 2L/a 50 40 30 20 10 0 ASCEIEPRI Guides 1989 S,l cv I') ~ C)' C)' t::::J" ~· I I I I I I -I ~ :;..., ....., 5 10 15 }~(';) /~fbr:'J _.r::,~<:J .,o")0 ,..o:i ......... 20 25 30 J_ a Vo/g 2 Ho I eo _..Q, ~ ~_. f\o ....a • ..... o.90 _0,95 _0 ,9a -0.99 35 40 Figure 2-22.-Waterhammer for valve opening. 2-40 ( 12) Addition of Hydropower to an Existing Water System. -Such systems are usually designed to operate under valve control and may have only a small waterhammer allowance. The addition of a turbine to the system can produce operating conditions that are uncontrolled (power failure), however the original design criteria for the pipeline should not be exceeded. So many variations of this problem are evident, the guidelines can only mention this situation. 3. Structural Requirements The criteria and methods for the structural design of penstocks for small hydroelectric plants are generally the same as those described in [ASCE/EPRI, 1989]. Additional infor- mation is available in [Arthur and Walker, 1970; Eberhardt, 1965; Gordon, 1978; Pirok. 1957; and White, 1924]. 'The penstock shell should be designed to withstand normal and emergency water hammer pressures without exceeding the allowable stresses for the mate- rial of the penstock [Gordon and Murray, 1985]. Normal waterhammer occurs when the unit shuts down under governor control 1be waterhammer pressures for any unit should be calculated by proper transient analyses. The methods to perform such analyses are doc- umented in [Rich, 1963; Parmakian, 1986; Davis and Sorensen, 1970; Streeter and Wylie, 1978; and Chaudry, 1979]. For preliminary estimates, the allowable waterhammer pressure should be taken to be between 25 and 50 percent of the static head. For high-head pen- stocks connected to impulse (Pelton) units, the allowable waterhammer pressure should be 25 percent of the static head. The needle valves can be closed slowly during the load rejec- tion while the fast acting deflectors limit the speed rise. The emergency water hammer condition may be caused by a malfunction of the turbine controls, such as rapid closure of wicket gates or needle valves or harmonic vibration of a valve seal or governor control cable. 'The emergency water hammer pressure should be taken to be at least 100 percent above the static water pressure. For normal water hammer pressure, the allowable stress in steel penstocks should be the lower of 60 percent of yield or 38 percent of ultimate tensile strength. For emergency water hammer pressure, it should not exceed yield strength or 61 percent of the ultimate tensile strength. The nature of allowable stresses is such that it cannot be appropriately addressed in the small hydro guides. It is suggested the reader consult the Conventional Guidelines on the vast array of papers on this subject. For plastic and fiberglass penstocks, there is a relatively larger margin of safety between the normal design and rupture pressures. 'Therefore, a design based on the normal water hammer pressure only should be adequate, with the emergency water hammer pressure allowed to encroach on the factor of safety. Approximate thickness of the penstock shell can be estimated by the equation for hoop tension alone: pr t=-f Hydro addition Structural requirements Criteria Waterhammer Stresses Hoop tension 2-41 ASCE/EPRI Guides 1989 Low pressures Design considerations Anchor blocks where: t p r f = = = = thickness of penstock shell (feet), maximum internal pressure estimated using the above-mentioned criteria (lb!fi2), inside radius of the conduit or penstock (feet), and allowable tensile stress in the material of the penstock as described previously, (lb/ft2). The final thickness of the penstock shell should be tested to ensure that the allowable stress in the shell material is not exceeded due to the combination of hoop, bending, and axial stresses. To avoid water column separation, each element of the waterway should be at or above the minimum hydraulic grade line. To cope with low pressures, the alignment of the penstock should be such that the top of the conduit is one-half diameter below the minimum hydraulic grade line, and preferably 1.5 diameter below it. If the conduit is not well below the negative surge line, it may start to "breathe" on every surge. This is caused by insuffi- cient internal pressure to maintain the shape of the pipe and the pipe may sag into an oval shape. If the pipe is supported on concrete saddles, and the "breathing" is almost continu- ous because of a low hydraulic gradient just above the top of the pipe, the metal may undergo fatigue and longitudinal cracks may appear above each saddle resulting in pipe failure. If discharge valves are provided at the low points and air vent valves at the high points along the conduit alignment, then it may follow the ground levels up and down the slopes, provided the conduit is always below the minimum hydraulic grade line. If the penstock or water conduit is made of welded steel and is laid underground, expansion joints may not be necessary. The strength, ductility, and elasticity of steel may be adequate to resist any stresses that may occur due to temperature changes. The temperature change to which a buried pipeline is subjected is relatively small. If the pipe is laid above ground, it should be supported on saddles or by ring girders and should be capable of free longitu- dinal movement This will relieve pipe stresses due to temperature changes. The unit stress in steel pipes caused by a temperature change of 50 °F would be about 9,500 lb/in2. However, inasmuch as the pipeline cannot be rigid or entirely fixed, the actual stress is somewhat less. Therefore, except under extreme cases, temperature stresses in ordinary steel pipes may not be excessive. It is desirable to make the closing welds on sec- tions of a pipeline at low temperatures, so that the resulting stresses are compressive rather than tensile. Additional stresses due to restraints provided by ring girders, supports and anchorages should also be taken into consideration. Concrete anchor blocks are commonly used for buried pipe installations to limit pipe movement at bends, reducers, and valves. The size of anchor blocks is dependent upon the internal pressure, pipe diameter, type of fittings, and the bearing strength of the surround- ing soil. For bends, the resultant thrust can be determined by the formula: ASCEIEPRI Guides 1989 2-42 R = 1.571U P sin g where: R = total resultant thrust (lb), D = outside pipe diameter (inches), P = internal pressure (lbfm2), and d = angle of bend (degrees). The bearing area required for the anchor blocks can be detennined using the allowable bearing pressure for the foundation material. Allowable bearing pressures for some soils are given in table 2-9. Table 2-9.-Allowable bearing pressures for different soils. Minimum, Maximum, Soil type lblinl lb/inl Alluvial soil 1,000 2,000 Soft clay 2,000 4,000 Sand 4,000 6,000 Sand and gravel 6,000 8,000 Sand and gravel with clay 8,000 12,000 Shale 12,000 20,000 Rock 20,000 30,000 4. Protective Valves, Gates, and Appurtenances The actual types of gates or valves used and their disposition in the system will depend upon the project layout and the way the turbine will function within the system. A detailed discussion of these items is included in [ASCEIEPRI, 1989]. In high-head plants with long penstocks, the intake should be equipped with a closure gate which can be controlled from the powerstation. The gates should preferably be equipped with a hydraulic operator. Air should be supplied to the conduit immediately downstream of the gate. This gate would be rapidly shut if a break is sensed in the power conduit to protect the powerstation from damage and to isolate the penstock. A valve (butterfly or spherical) should be provided in the powerstation to permit maintenance on the turbine without requiring the draining of the penstock. Francis units installed in medium head plants are normally supplied with wicket gates. If the penstock is relatively long or there is more than one installed unit, individual butterfly valves should be provided at the powerstation. If the penstock is relatively shon, the intake gate may be used as a protection. It should have a hydraulic operator and be capable of closing against flow in the rare case of malfunctioning of the wicket gate. Airvalves should be installed at every summit point or locations of abrupt changes in the profile of the Bearing pressures 2-43 ASCE/EPRI Guides 1989 Blowoffs Coatings for penstocks pipeline to pennit the release of air that may accumulate during pipe filling and to allow entrance of air during pipe draining [Lescovich, 1972]. A blowoff should be installed at each depression along the pipeline where necessary, so that all water may be drained from the pipe. This usually consists of a short length of pipe cormected to the bottom of the main pipe, and carried sufficiently away from the main pipe to enable a gate valve or other device to be installed. 'The size of the blowoff depends on the length and size of pipe to be drained, and the pressure available at that point To detennine the size of the outlet. the blowoff may be treated as an orifice capable of draining the volume of water in the pipe within a reasonable time with the average head available during the draining operation. Suitable manholes should be installed on all large size pipes at not more than 1,500-foot intervals, at convenient locations to allow access of worlanen and materials into the pipeline. 5. Protective Coatings For Penstocks Some of the commonly used protective coatings for penstocks include the following: • Epoxy enamel for steel penstocks. Primer may not be required with this coating. The penstock is cleaned to white metal and the coating is spray-applied in one (28 mils wet coat) or two coats as detennined by surface exposure conditions within hours to prevent rust bloom from appearing on the metal. • Bitumastic coatings for steel penstocks. Steel preparation requirements are the same as for epoxy enamel. The application, however, can be made with brush, roller or spray and is made with thinner coats. 1\vo coats of 10 mils wet fllrn are recommend- ed. Primers may be used with coal tar epoxy systems if scheduling prevents the clean- ing and paint applications in rapid sequence. The prime coat, however, is to be con- sidered as the weakest link in the coating system and the most likely element to be the cause of failure. • Epoxy for steel penstocks. This coating uses a primer. It is a high solids coating which cures to a very hard surface and comes pigmented in a variety of colors. 1\vo coats of 8 mils wet thickness are recommended and are applied with roller, brush or spray. • Spray coating with tar for wood stave penstocks. • Lead and rubber based paints for steel penstocks. • Polyethylene, cement, and concrete coatings for steel penstocks. • Cathodic protection for steel penstocks in soils with reactive characteristics. • Zinc or bitumen coating or polyethylene sleeving for ductile iron conduits. • Plasticized polyvinyl chloride sheet keyed into concrete pipe walls and cemented to smooth-walled steel pipes. ASCE/EPRI Guides 1989 2-44 E. TAILRACE CHANNELS The main purpose of a tailrace is to provide a means to return the turbine flow to the natu- ral waters on the downstream side. On a reaction turbine the elevation of the tail water in the tailrace influences the operation of the turbine and determines the net head available to the machine. Therefore, careful con- sideration must be given to establishing the tailwater elevations for all flow ranges from the turbine to the natural receiving water. A tailwater rating curve should be developed for all flow conditions. In reaction turbines the exit velocities into the tailrace are governed by the draft tube design and are usually restricted to the 3-to 5-ft/s range. To meet this requirement the out- let of the draft tube must be constantly submerged. This submergence varies with the draft tube type, but is usually a minimum of 1 foot Therefore, the tailrace must be designed to ensure that draft tube submergence is maintained. The tailrace may be designed with grad- ually varying cross-sectional areas so that the tail water elevation does not vary rapidly with large changes in flow. A major concern for tailrace designs with impulse turbines is that the tailrace efficiently transports water away from the runner and does not cause negative pressure that may draw the water up into the runner. Therefore, the tailrace must be designed so that during rela- tively high flows, such as a 25-year event, the water in the tailrace is low enough not to flood the runner or allow negative pressure to build up in the runner case. At least 1 foot clearance should be allowed between the high water elevation and the top of the turbine discharge vault. The exit velocities from an impulse unit can be quite high. In addition, because an impulse unit is located above the stream bed, the fall of water to the natural water course can have high velocity. To protect against possible erosion of the tailrace area, rock riprap, concrete aprons or a combination of the two should be added between the powerhouse and the stream as shown on figure 2-23. 'The tailrace should be designed so that water can exit freely and smoothly from the turbine pipe. The tailrace should be situated so that it will not collect debris or sediment from the natural water course, especially under high flow conditions. The location of the mouth of the tail- race relative to the natural stream course is an important consideration to minimize debris collection and sedimentation. Future streambed degradation may require an artificial sill around the powerhouse discharge to prevent turbine drainage [Moore, 1988]. Tailrace channels Reaction turbines Impulse turbines Debris In very cold climates icing conditions may cause serious problems in the tailrace. Both Icing frazil and anchor ice can prevent plant operations for prolonged periods. To keep the tail- race channel functioning under ice conditions, design it as deep, uniform, narrow and free from turbulence as possible. A covered tailrace may be required in some cases. To avoid turbulence, keep the tailrace velocity less than 2 fils and eliminate irregularities or obstruc- tions in the tailrace channel. The design of a tailrace can have major impacts on the fisheries resource. The tailrace must be designed so that the exit flow does not attract anadromous fish into a dead-end situation. 2-45 ASCFJEPRI Guides 1989 r \ 1"e.'"'"' :!P•o<..&: t......a ClJo.L ~.14q4.0 D .(\ ) 0 1. ~ 2 e \ )- ~ &. .,.. "") ~ ~~ .,. ~·-c:: • s-z.'·e· f"'"" e.e.,.;ou~ !:". '-E'-iAq t.. 0 ~.._o...e: 1"t:> De.t>-1>--1 ,..w~'< !=1:.0""' ,..,e: coo"" '"-e..>-~ owse. I~ ,.,,.IUp..,~IN"''t...iM \ Figure 2--23. -Tailrace design to prevent erosion. Courtesy Ott Water Engineers. 2-46 ASCEfEPRl Guides 19&9 ~··o··.l!loZ.··e.· !='!:::>""' liii:II:.~-<OW.3e:. ;:;c::-1!.1... ~.s.o = Figure 2-24.-Tailrace fish barrier (1). Courtesy Ott Water Engineers. 2-47 ASCEIEPRl Guides 1989 Fish barrier P'~CA"T'& ........, ... ._. ..3T""&EI.-~ e,~Uo.C:...O..IET" ~ z.- 1'1_" G:AI...I./. ~T"'U!.~ """'~T":!> ,...,. c:.oo...c:L.C..-e.. ~s ~) ::.A""I!!!.TV c.oa~ ~1 AU-VV~~ Ae....G:; ~:Tt-ltc...t:.. Hj•!!!. c:!,.ll.. CAD-.1 T'O!.e::JI!:D Figure 2-25. -Tailrace fish barrier (2). Courtesy Ott Water Engineers. The tailrace should include an upstream fish bypass such as a fish ladder or bypass channel to allow the fish to move on upstream without entering the draft tube. If the exit velocity from the draft tube is less than the darting speed of the fish, say 10 to 15 ft/s, a bar rack may have to be placed at the entrance to the tailrace. This rack should have openings less than 2 inches and be placed parallel to the flow in the receiving water. Tailrace fish barriers are shown on figures 2-24 and 2-25. ASCE/EPRI Guides 1989 2-48 F. HYDRAULIC MODEUNG The decision to perfonn hydraulic model tests for any component of a small hydroelectric project should be based on a comparative evaluation of the cost of modeling and savings in the construction, operation and maintenance costs or increase in project benefits likely to result from the model tests. Usually, the designs of spillways, energy dissipation arrange- ments, sediment control devices, fish passage facilities, intakes, outlets, and other control structures for small hydroelectric installations are based on experimental and empirical infonnation. Hydraulic model tests may help in the refmement of designs taking site-spe- cific conditions into account In most cases, the initial cost of hydraulic modeling may be justified by the savings in capital or recurring maintenance costs even in the case of rela- tively smaller structures. Due care should be taken to model only those components where available design infonnation is not adequate and the proposed hydraulic modeling is expected to yield an improved design of that component. The principles of hydraulic modeling are described in [Gulliver and Wetzel. 1984; Davis and Sorensen, 1970; chs. 3 and 23, ASCE, 1942]. G. DOWNSTREAM FISH PASSAGE 1. General This section describes stationary and movable screens suitable for preventing fish from entering the turbines at small hydroelectric installations. The most important factors for the design of these screens are: • The approach velocity to the screen • Adequate transportation flow to carry fiSh and debris past the screen • Unifonn velocity distribution over and through the screen • Facility for continuous or periodic cleaning of the screen The two primary components of a downstream juvenile fish bypass system are [Rainey, 1985]: • Effective screen system -which minimizes fish entrainment and accommodates debris. • Effective bypass system -which minimizes impingement by collection and trans- portation of juvenile fish back to the receiving water with a minimum of injury and delay. Most state and federal fish and wildlife agencies have set standards for approach velocity, through screen velocity, bypass flows, and cleaning frequency and mechanisms which vary depending on the species of fish to be protected and the types of screens to be used. Hydraulic modeling Downstream fish passage For example. the California Department of Fish and Game's [1982] General Fish Criteria Screening Criteria require that the local approach velocity component perpendicular to the screen face should not exceed 0.33 ft/s, while the component of velocity parallel or adja- cent to the screen face must be at least 2 times the allowable approach velocity. The clean- ing criteria require that continually cleaned screens should have a minimum open area of 2-49 ASCE/EPRI Guides 1989 Approach velocity Screen design Types of screens Stationary screens 1.5 ft2Jft.3/s of diverted flow, and screens not continually cleaned should have a minimum opening of 6 ft2Jft3Js. Round openings in the screen shall not exceed 5/32 inch and slot openings shall not exceed 3/32 inch in the narrowest direction. The U.S. National Marine Fisheries Services has similar requirements for its fish screening criteria [NMFS, 1982]. For juvenile salmonids it specifies a limit on approach velocity for salmon fry (length less than 2.4 in) of 0.5 fils and for salmon fingerlings (length greater than 2.4 in) of 1.0 fils. It is further required that the component of the velocity parallel and adjacent to the screen should be at least equal to the approach velocity. The National Marine Fisheries Service also cautions that the velocity parallel to the screen is very site dependent and should be handled on a case-by-case basis. Screen openings must not exceed 1/4 inch in the narrow direction for fmgerling salmon and 1/8 inch for fry. Screen material should provide a minimum open area of 40 percent. Cleaning is required as fre- quently as necessary to achieve the flow and velocity criteria. In both of these examples, the agencies stress that the screens provide even distribution of flow over the surface and through the screens, i.e., high velocities in localized areas, should be eliminated. In the design of screens, punched aluminum plate and wedgewire are the most common materials used to meet the requirements for the sizes of openings or perforations. The most difficult task is to ensure a uniform velocity over the screen and maintain this uniformity as debris collects on the screen face. As debris collects, portions of the screen may clog and create higher velocities at other locations on the screen. The increased localized velocities may result in fish impingement The engineer should work with local fishery agencies to obtain the types of fish and their size and migration habits. At some sites screens may not be warranted. In others screening criteria may already be established for a particular species of fish. 2. Types of Fishscreens The following types of screens are particularly suited to small scale hydroelectric projects including both high-head/low-flow and low-flow/high-head installations [Taft, 1986; Leidy, 1986; and Eicher, 1985]. a. Stationary Screens with Brushing Mechanism. -This type of screen utilizes a screen usually made of wedgewire or punched plate, set in a vertical position. The water approaches the screen at a slight angle from parallel. As the water passes through the screen the debris stays on the screen until a brushing mechanism or high-velocity bypass flow sweeps it on downstream with the bypass flow. The standard punched-plate screens frequently used by the California Department of Fish and Game are illustrated on figure 2-26. The screens are 3/16-inch punched plates with 5/32-inch holes on 7/32-inch centers. They are continuously cleaned by a brush mechanism that sweeps back and forth driven by a cable and pulley system. The brushing mechanism can be powered by a reversible motor and, in some cases, installations have used paddle- wheels (fig. 2-27) on the downstream side of the screens to drive the mechanism. A prob- ASCE/EPRI Guides 1989 2-50 Figure 2-26. -Stationary screen with brushing mechanism. --~L. 01<:. F'IPE. Figure 2-27. -Paddle wheel screen. - 2-51 ASCE/EPRI Guides 1989 Flat-plate screens Velocity Cleaning lem with punched-plate screens with regard to cleaning is that they require power at the diversion site if a paddlewheel is not used. When installed at higher elevations, ice buildup may occur thus impairing operation. Under such circumstances, the screens are usually removed during the winter period. Pine needles and small rocks of the same diameter as the punched holes tend to wedge in the holes and clog the screen. Because of the continuous motion of the brush sweepers, a critical design problem is the sizing of the cable and pulley. Depending on the drag of the system, different size pulleys and cables are usually tried at the installation before an optimum size is determined. A counterweight ann is usually added to keep the brushes pressed against the screen as it is brushed. Electronic sensors are normally installed to measure differential water head on the outside and inside of the screen and to warn the powerhouse if clogging is occurring. A special clogging problem occurs in streams that are high in algal content during the sum- mer months. Control of some types of algal growth may require repeated hand brushing. Special coatings have been used to retard algae growth. Provisions must be made to make sure that the bypass flow parallel to the screens is adequate to draw away debris that is car- ried to the screen face, as well as to guide fish downstream and away from the intake. b. Inclined, Flat-Plate Screens. -flat-plate screens are usually inclined to the flow. These screens are made either of wedgewire or punched plates (figs. 2-28 and 2-29). The screens are cleaned by rotating them into the flow and allowing the debris that has accumu- lated to be washed off and passed through the turbine and on downstream. There is a possi- bility that fish would also pass through the turbine during the brief time these screens are rotated, but fish exposure can be minimized by timing screen cleaning to periods of reduced fish migrational activity. The length of time that the screens would stay open would depend on the water velocity and the amount of debris on the screen. Inclined screens are effective in passing large volumes of flow; however, they require power at the site in order to tilt the screens. Also, they allow debris to pass through the turbine during cleaning. Usually, the trash rack located upstream from the screen is designed to prevent large debris from passing to the turbine. The principal challenge with large, flat plate screens is to obtain a uniform velocity over the screen face. If the screens are immediately upstream from a turbine, the flow pattern created by the turbine inlet must be considered to avoid nonuniform flow over the screen face. On larger installations, physical hydraulic models should be used to develop designs which would ensure uniform velocity distribution over the screen face. Other screen designs of this type that do not have a mechanical cleaning mechanism usual- ly require a much higher velocity past the screen face to carry debris away. In some cases, the velocity past the screen must be four to five times the velocity through the screen itself. A typical example of this screen type, often referred to as a high velocity passive pressure screen [Eicher, 1985] is shown on figure 2-30. This type of screen can very effectively be installed in the penstock itself to make use of the uniform pressure in the conduit. ASCE/EPRI Guides 1989 2-52 - Figure 2-28. -Inclined stationary screen. MAIN~ 1=\.USHING I=OSITION Figure 2-29.-Powerhouse intake structure showing ftshscreens. [Wagner, 1984]. I ,,. / Cleanon~ PO!Oition -= ... Figure 2-30.-Pressure wedge-wire screen in turbine penstock. [Eicher, 1985]. 2-53 ASCE/EPRI Guides 1989 Coanda screens c. Coanda Screens. -The Coanda screen, shown on figure 2-31, is an old concept revived from the mining industry where it was used to separate coal and mineral ore from a water slurry system. The screen was used to pass the debris and other materials off the screen while the water dropped through the screen. This screen type is now used to effec- tively pass debris and fish over the screen while requiring very little cleaning effort. The Coanda screen utilizes the Coanda effect (that is, the tendency of a jet of water to follow the wall contour) to draw water through the screen. The horizontal wedge-wire screen is shaped in an ogee spillway-type configuration as shown on figure 2-31. It has been used to pass 70 ft3/s on a 3,000-kW site and has run 3 years with no clogging, debris, or fish impingement problems. The slot-size between the horizontal wedgewires is about l/25 inch and, therefore, there is no opportunity for small fish to enter the turbine system. A disadvantage is the screen type is that the screen requires about 3.5 to 4 feet of head in order to pass the water over the ogee and down into the collection system. Also, in certain climates, it has been found that algae can grow on the underside of the screen face. Scrubbing the underside of the screen with soap and water once a year appears to eliminate this problem. The design of Coanda screens should include special considerations for flow variations. When discharge drops, all the water may enter the upper screen face and leave the bottom portion of the screen dry. Thus, there is a possibility of impinging fish on the dry surface. To correct this problem, a V-notch weir arrangement can be placed at the top of the screen to concentrate the flow so that it is always wetting the end of the screen and thereby carry- ing the fish and debris downstream. In general. these screens have been found very effec- tive and inexpensive. Design considerations allow them to handle 1 to 1.5 ft3/s per lineal foot of screen. d. Circular Screens. -Circular screens make use of wedge-wire in short, stubby pods. These screens are now gaining common use in the small-scale hydro field. The IXXis have the advantage in that they can be placed effectively under the streambed to collect water in a manner similar to an infiltration gallery. They may be placed in the configuration shown on figure 2-32. The advantage of circular screens is that there is very little head loss if the fish velocity criteria are met. When placed in a group, circular screens can collect large volumes of water on low head projects without excessive head loss. The minimum slot spacing between the wedgewire ensures that fish and debris cannot enter the turbine. Oeaning of the screens can be achieved by several methods. The two most common are air and water backwash systems. For the air backwash, pipes may be placed inside the pods to provide a burst of air from an external source, which may be a permanent or portable com- pressor. Care must be exercised to place the discharge pipe so as to evenly backwash the entire screen and not add air directly into the penstock. The hydraulics of these screens is discussed by Fournier [ 1980]. Some screens do not backwash but rely on high bypass water flows to sweep the debris on downstream. These are screens are discussed by Richards [ 1980]. ASCE!EPRI Guides 1988 2-54 ' FISH BYPASS ' ...... , .......... "' Figure 2-31. -Coanda screen. \&=T!c;.:.L ;:ax) }HI s..;;=•a wl~! Figure 2-32. -Cylindrical wedge-wire screen. [EPRI, 1986]. 2-55 ASCE/EPRI Guides 1989 Rotary drum screens ... = , . . . ' . .. ' . . ELECT~JC SCRE~N O~!V! UN!T . ' .. '... . . : , ·,' Figure 2-33. -Drum screen -elevation view. e. Rotary Drum Screens. -Drum screens are commonly used at hydroelectric and irriga- tion diversions throughout the western United States (figs. 2-33 and 2-34). Their effective- ness in screening fisheries depends on the following factors [EPRI, 1986]: • Orientation of the screens • Easy escape routes to the bypass system Orientation of the screens should be such that the sweeping velocity parallel to the face of the screen (direct toward the bypass) is at least two times the approach velocity to the screens. The bypass system should be designed so that the fish may enter the bypass immediately in front of the screen face. Power to drive the screen can be electric with a chain drive as shown on figure 2-33 or by a paddle wheel arrangement as shown on figure 2-34. ASCE/EPRI Guides 1989 2-56 T rasl'ltock -s" Openi n; m th• cl-··· -~ ..... I • I •, I ' I ' I I : : t: I I I I I I I I I I I . \---·-·-16' -0" ·+-,-+ .. -· \ I : ' ' t I , ' I I ' '..... I I; / ........ ~-i-4-/ LlJ~ l Sluice PIP<I \ \ I I I I I I Figure 2-34. -Rotary drum screen. [EPRI, 1986]. I I d Criteria for hole size and speed of rotation of the screen depends on local specifications for fish protection and debris and ice conditions. See [EPRI, 1986] for a summary of criteria. f. Bar Screens/Racks/SubnuJrged Tracking Screens.-Bar racks, because of their spac- ing, are usually designed to physically block large fish while possibly pennitting small fish to pass through. The EPRI [1986] study concluded that smaller fish may not pass through in some cases because the hydraulic conditions established by the racks may cause them to avoid it. The study concluded that more research should be conducted on these racks. Bar screens can be spaced so that small fish are also physically blocked from entering the turbine (fig. 2-35). These types of screens divert downstream migrants into an intake gate well, usually in an upward direction. The fish pass up the gate well to a collection facility where they can be released below the dam or trucked to another location. Screens 2-57 ASCE/EPRI Guides 1989 Traveling screens 0 % ~ 4 Figure 2-35.-Installation of bar-screen in turbine intake. [Farr, 1974]. g. Submersible Tra-veling Screens. -On very large rivers, it may not be feasible to design a fish screening system that physically excludes all fish. For example, at Bonneville Dam Second Powerhouse, each of the eight turbines has a maximum design capacity of approxi- mately 20,000 ft3/s. The problems of physically excluding fish from 160,000 ft3/s at this site are monumental. The submersible traveling screen (STS) (fig. 2-36) has been devel- oped to provide panial fish screening at sites like Bonneville and still achieve adequate fish protection. STSs take advantage of the downstream migrational behavior of salmonids. In general, the great majority of fish migrate near the surface of the water column. Thus, as the surface waters are drawn into the turbine intakes, much of this water and the fish in it passes near the intake ceiling. An STS extending into the intake from the ceiling will potentially intercept this water volume and the associated fish, and consequently, allow the intercepted fish to be safely guided out of the intake and around the turbines. ASCE/EPRI Guides 1989 2-58 III[" f!J!!!ACE OfttFIC[ ----+H-C ITNS S 8ALU:JitY ---H.,_ VDTlCAL Figure 2-36. -Submersible traveling screen at turbine intake. The STS consists of two large rotating screens with a perforated plate placed between them. A steel frame provides support for the screens (fig. 2-37). The upstream face of the screen travels up the face of the unit, allowing debris to pass over the screen. The perforat- ed plate restricts flow, and consequently velocity, through the screen material, thus prevent- ing injury to fish which might become impinged on the upstream face of the screen. The STS relies on intercepting both fish and water. The water passes either through, beneath, or around the screen or into the gate well. That portion of the flow traveling upward into the gate well will carry with it the fish collected in front of the screen. IIOLL£111 Figure 2-37.-Schematic of submersible traveling screen. Flow description 2-59 ASCE/EPRI Guides 1989 Fish guidance efficiency Louvers Velocities Spacing Louver angle Properly functioning STSs should successfully guide 85 percent or more of the fish poten- tially interceptible. Guidance efficiency problems may arise when flow conditions in the turbine intakes result in fish avoidance of the screen, i.e., actively swimming away or under the screen or passive deflection around the screen. In addition, if the fish are not dis- tributed near the intake ceiling when approaching the screen, they will not be intercepted and guided safely from the turt>ine intake. A careful understanding of forebay flow pat- terns, hydraulic conditions at the turbine intake, and the vertical distribution of fish at the intake is required to properly design a STS fish guidance system. h. Louvers.-A louver system consists of a series of vertical slots evenly spaced 1 to 3 inches apart across an intake channel. The array is angled to guide fish to a bypass channel. Fish detect the hydraulic turbulence created by the louver and move laterally away and gradually downstream to the bypass [EPRI, 1986]. The major design considerations in a louver system include: • Type of fish and their swimming speeds • Approach velocity of the flow • Spacing of the louvers • Angle of the individual louvers to the flow • Angle of the louver line to the flow The types of fish and their swimming speeds should be obtained from local fisheries agen- cies. Usually, the approach velocity varies from 1 to 7 fils (usually about 3.5 fils). However, these velocities are usually set to hold a particular bypass channeVapproach velocity ratio. These ratios vary from 1.3 to 2.0 depending on the fish. In any case, bypass-channel veloc- ities should be at least 1.5 times the approach velocity and should always be higher than the sustained swimming velocities of the fish. Spacing of the louvers used range from 1 to 3 inches with l-inch spacings being the most common. Hydraulic analyses should be conducted on the spacing, angle, and width of the slates to compute head losses. Angles of the louvers and the relationship between swimming speed and approach velocity are shown on figures 2-30 and 2-31 [Bates et al., 1960]. Successful angles oflouver arrays range from 12° to 22° (the most common being around 15°), with the angle of individual louvers set close to 90°. Past studies on existing projects using louvers are summarized in [EPRI, 1986]. ASCEIEPRI Guides 1989 2-60 I ?' ... rn..J:N t • .... v & • -..o< VS.X%T'r a' III.OW IN I'IZT -51~ v1 • SWIMo4ING lll'!l!:l r:11' ll'l$0 IN ll"'!lET -51~ V • 111$..1. TAHT IOiil!l't!N'f r:11' ll't$0 tN 1"1!:1' -Slc::Hl I • NG...I a' THE I.I!'E a' ~ Figure 2-38. -Louvers. [Bates et al., 1960]. 7.0 0.97 . ., .1·--l.46 1.69 :.~~ Z.l6 I :.9e :l.SO 4.01 "f·"' 4.93, 6.5 0.90 1.13 1.35 1. 79 2.01 6.0 0.8~ 1.04 1.25 l.!S 5 • .5 O.ii 0.95 1.14 1..:;:5 :.70 5.0 O.iO O.Bi 1.0~ L:l! l.JS L.54 4.5 0.63 0.78 0.94 1.09 1.39 l.lO 3.3 0.49 0.61 0.73 0.96 !.OS 2.2: 2.C5 :.as t. il !..54 !. 37 !.:0 : • .54 , ---·.J• 3.2! 3.7) ).00 : .. 7S ~.1: 2.so 2.e7 1. 90 2. 25 z.: e t.c9 z.oo z.29 1.48 I. 75 2.01 ' , • •o' ~·:~ q.~ I ).~=,4-24! J • .:-3.8, i I ::.:: ~-54, ! 2.!? ::1.181 : . .:-; 2.ul 3.0 0.42 0 • .52 0.62 O.ij 0.83 0.93 1.03 1.27 1 • .50 1.72 1.93 Z.l1 2.s o.:t.s 0.43 o.s:! o.6o o.69 o.n o.e.s 1.06 1.:s l.43 ! .61 1. 77 2.0 0.2! 0.3.5 0.42 0.¥8 o.ss 0.5: 0.68 0.!5 1.00 1.13 1.2' 1.41 l.~ 0.2l 0.26 0.31 0.36 0.41 0.46 O.Sl 0.63 0.75 0.!6 1.0 0.14 0.17 0.21 0.24 0.25 O.ll 0.34 0.42 0.50 0 • .57 8 10 12 14 116 Its 20 2.5 30 £.:.!: 2. c = I o.~.:. o. 11 ~c I 4! I 1 Values underlined represent combinatioos of approach flow velocities and male• of lines of louven negotiable by fuh capable of swimming at 1.0 fl/s. Figure 2-39. -Louver vector analysis. [Bates et al., 1960]. 2-61 ASCEIEPRI Guides 1989 Upstream fish passage Fish way types De nil fish way Weir and pool fish way H. UPSTREAM FISH PASSAGE 1. General The objective of upstream fish passage facilities is to collect fish below the barrier, with as little delay and hann as possible, and return them to the impoundment above the barrier by their own volition through an artificial channel, lift. or truck. The criteria and methods for the design of upstream fish passage for small hydroelectric installations are generally the same as those for Conventional Hydroelectric power plants and are documented by Eicher [1985], Bell [1980], Johnson et al. [1978], Hildebrand [1980a; 1980b; 1981], and Orsbome [1985]. 2. Types of Fishways The various types of upstream fishways suitable for small hydroelectric powerplants include the following: a. De nil Fish way. -The Denil fishway is an open flume with baffled walls and floor. The baffles are oriented in such a way as to create return flow at the walls and floor which slows the core flow. The fishway can then be set on a relatively steep slope, usually 6H: 1 V, and maintain a maximum velocity less than 4 ft/s. The Alaska Steep Pass is a Denil type that has been placed on slopes up to 4H: 1 V [Ziemer, 1962]. These fishway designs are effectively applied to areas where there is limited space. These types of ladders can be pre- fabricated and may be less expensive than the fonned concrete type. Since there are no pools or resting areas in Denil sections, the ladder must be provided with resting areas after approximately 6 feet of elevation gain. The Denil has the advantage of operating over a range of 3.0 to 3.5 feet of tail and headwater fluctuation, which is ade- quate to cover the range of flows at most small hydropower sites. A simple Denil fishway is illustrated on figure 2-40. Rajaratnam et al. [1987] suggest the use of a roof installed at a height of three times the width of a Denil where the depth to width ratio exceeds 3. This will result in a two-level Denil for high flows. Finer bed mate- rials, e.g., pebbles and sand get naturally flushed from the fishway; cobbles may require hand cleaning. b. Weir and Pool Fish way.-Many of the older ladders at dams are of this type. They are a series of pools with water flowing from pool to pool over rectangular weirs or stop logs (fig. 2-41). Pool widths vary from 4 to 8 feet with lengths of 6 to 10 feet As the headwater fluctuates, the fishway flow increases or decreases depending upon the head on the upstream weir. The result is often a fishway with too little or too much flow. On the high end, power generation may be decreased and the fishway made impassible by a velocity barrier. On the low end, the fishway may be nearly dry with insufficient attraction flows. In addition, this type of fishway may experience dissolved oxygen deficits during high-tem- perature and low-flow conditions. ASCE/EPRI Guides 1989 2-62 DENIL FISHW&'f A POa... l.£NG1lj 1 2-0 2'-6 B POOL WIDTH ~ 4' c WATER DEPTH -:t-5 z -5 D BAFFLE Wlont 7.5 10 E SLOT W101lf 1.75 2'-4 F earTOM SAFFI..£ NOTCH HT. 9" 12" G FLOOR SlOPE 1:6 1:8 DISCHARGE VARIA8L£ CFS-ZI AV. VEL. 4 FPS t. (BAFFLE SPllCING) Figure 2-40. -Schematic of Denil fish way. -~ 10 Figure 2-41.-Typical weir and pool fishway. Like the Denil type, standard weir and pool fishways will not readily pass bedloads and must be designed with bottom orifices if this is a concern. As mentioned by Oay [ 1961], weir and pool systems can oscillate between streaming and plunging flow. This instability appearing as roll waves on pool surfaces can compound to a point where the fishway becomes ineffective. This problem can be avoided with proper design of weir crests and bottom orifices. However, flow regulation remains a major prob- lem. A sample weir and pool fishway is shown on figure 2-41 and a modified version on figure 2-42. c. Weir and Orifice. -Weir and orifice fishways have been used for a number of years to pass salmonids and herring species. The designs involve a modification of the standard weir and pool that incorporate bottom orifices, both flush and re-entrant types, and often notches in the weir crest. A popular weir and orifice design is the ice harbor fishway; Weir and pool Weir and orifice 2-63 ASCEIEPRI Guides 1989 Ice Harbor Slotted fish way Self- regulation Trap and haul whose name comes from its early application at Ice Harbor Dam near the mouth of the Snake River in Washington. The Ice Harbor design has either one or two bottom orifices that will pass bedload as well as fish. Fish generally prefer orifices to jumping over weirs. The upstream side of the weir is provided with two baffles oriented normal to the weir and parallel to the general direc- tion of flow. Due to the baffles, orifices and weir crest shape, the unsteady flow problem mentioned in the previous section does not occur. Like the weir and pool fishway, the Ice Harbor design requires flow regulation and is best applied to locations with little or no headwater fluctuation. A half ice harbor weir is shown on figure 2-43. d. Vertical Slotted Fishway. -The slotted fishway was first constructed in the early 1940s at Hell's Gate on the Fraser River in British Columbia. In 1985 the Fraser River slotted fishways passed the largest salmon run known to ascend a manmade fishway. Early success of the slotted fishway has made it the most common design in Pacific Coast fishways. Pool sizes vary from 20 feet wide by 18 feet long to 4 feet wide by 5 feet long. Baffles between weirs are fashioned with a vertical slot that may extend to the floor of the fishway. All fish, water, bedload, and debris pass through this slot. Slot widths vary typi- cally from 18 inches to 6 inches. An 8 foot wide by 10 foot long pool with a 12-inch slot width is probably the most common design. Figure 2-45 shows a typical slotted fishway. The principal advantages of this design are the self-regulation of flow. adequate resting areas for fish, and operation with nearly any depth of flow [Oay, 1961]. Self-regulation of flow in the fishway is important since most small hydropower projects have a substantial variation in head differential at diversion works. The slope of the slotted fishway is set such that during the maximum water surface difference, between head and tailwater, the head loss per pool is one foot. The head loss per pool for a smaller water surface difference is less than one foot. The vertical slots will not maintain a constant discharge over the range of water surface fluctuations; however, hydraulic characteristics of the fishway are constant and, therefore, useful to fish over the range of design flows. e. Trap and Haul Systems.-Trap and haul systems are best applied to barriers of sub- stantial height (say greater than 100 ft) or compound barriers. In situations where dewa- tered reaches are long or a dam is several hundred feet high, it may only be possible to trap fish at the base and truck them safely upstream. A trap and haul system typically consists of a ladder section leading to a holding pool. From the holding pool, fish are crowded toward an elevator which transports them to a truck. The ladder section of the trap can be of any type, though self regulating features and debris and bedldad passage are not important considerations. Weir and pool, and weir and orifice type fishways are common at trap installations. Between the holding pool and the last fishway pool, a trap device may be installed that pre- vents fish from leaving the holding pool and returning back down the fishway. Three com- mon trapping devices include the V-trap, finger trap, and jump-over weir. These devices are discussed in [Bell, 1980]. Figure 2-42 shows the last two designs. These traps become increasingly important as fish are held greater lengths of time between haulings. ASCE!EPRI Guides 1989 2-64 _....,;' F F .. .. .. .. : .. .. :! :· . .. ··. .. .. .:· ......__ ~ .....___ I ,---... .. ~ .. F ... ~~ .1 . . \ \ Orifice ......__,.. ~ .........__,_ _A !One A A STREAMING OR SHOOTING FLOW a. Entering ftow below critical. F Orifice PLUNGING FLOW b. Entering ftow above critical. A Pool LenQth 6-20Ft. a Pool Width 6-20Ft C Orifice HeiQht D Orifice Width 16" -1811 E Polltlon of Orifice Vertically 4.25 Ft F W* Height 6Ft Drop Per Pool 12• Mcud111um Figure 2--42. -Typical weir and pool fishway, modified. [Bell, 1984]. 2-65 ASCFJEPRI Guides 1989 Holding pool Flow and design ~ Q H - The holding pool is the area where fish are held in between loading cycles. Fish may be held for several hours before loading though it is preferred to haul at least once a day and more often if runs are heavy. There are two principal design considerations for the holding pool, volume and flows. The size or volume of the holding pool is determined from the space requirements for holding fish. [Bell, 1980] suggests 0.3 ft3 of water per pound of fish. The number of fish depends upon the cycle time of trucks and arrival of fish at the facility. In a simple case, if fish arrive at a trap at a rate of 200 fish per hour and a single truck is used with a capacity of 200 fish and a one-hour cycle time, 600 feet of holding pool would be required if fish average 10 pounds in weight. Flow to the holding pool is introduced by floor diffusers at velocities between 0.25 and 1.0 ft/s. The minimum holding pool flow is determined from the oxygen requirements of fish and the dissolved oxygen available in the water. These computations are easily performed when consumption requirements are used in units of oz/lblhr and oxygen concentrations are given in ozJft3. In general, oxygen requirements for fish vary between 2.5 x IQ--3 and 1.0 x to--2 oz/lb/h, and dissolved oxygen concentrations of fresh water vary between 0.013 and 0.010 ozJft3 (for saturated conditions at 40 to 60 °F). Consumption level depends upon the activity and species and it must be recognized that only 40 to 60 percent of available dissolved oxygen is useful to fish. B ~ "I' H ., Weir en.t T E A Pool l.enqtn 8-20 F't 8 ~Width 6-20Ft C Onflee Heiqllt IS ln. End VIew 0 Or~fiee Width 15 lrt E ?o!lltion at Orifo::e Vertically 4.25 Ft F Weir Heiqll t 6Ft. - I I G Winq &lffle Heiqnt 8 F't. I I ._._. ,/'j I --:~ t~ ~ ',1 Flow l; E ··;: .. , . F CD ~: : .. ... F ·• ffl .li ,. ~ " "'' w'l'• H Position at Winq Baffle 1.5-5 F't. I Wldtn 1.2 at B ',...,. ,,... .. A m;:>Jnl(\ A """ ~ Figure 2-43. -Ice Harbor weir crest. ASCE/EPRI Guides 1989 2-66 "' A POOL L.ENGTH 6' i POOl. WIDTH 4 T WIDTH IFI"LE HEJGK' NIMUM ORIFICE: SIZE 6 lj rEH ;PTH l'f NUl' ;H 12 0 I'IICFS MIN 1.65 ICifiMAL !5D MAX 2-4.0 ORa' P£R POOL 9 ·12 a· I. 8 X 4.0 12.3 360 9-12 10' 8 fr 1.! ),5' 5.2!5' 10 l( 1!5 4.0 !:.~ 9 ·12 POOL. AHJ WEIR F1SH._., Figure 2-44.-Dimensions of pools at Cabot Ladder, Connecticut River. '\ A Pool l.IIIQtll 6 ~ id B Pool Wlditl ... g « c Watw deofll (Mini i 'S 'S 0 Slat Wlcltft 5 .75 1.0 E Wf!!J Baffle L!!!2!11 g·: 11-J.&i' 1'-3.63" F Wlnq Sotf._ Olsfo~~Qt 2' 3' -4" 3'-7" G Ol!p!oc:-.nt of Bottle if ~-:t 5'-5' Discharge Pet Foot of O.tll Alllwe Block in CFS 32 4.8 6.4 Orop Pet Pool I' I' I' Figure 2-45.-Vertical slot fishway. [Bell, 1984]. Sill Block in P!oce 2-67 ASCEIEPRI Guides 1989 Crowding Tank trucks Lock and lift Selection of passage Auxiliary Fish may be crowded from the holding pool to either an elevator or hopper that raises fish to an elevation above the tank truck. Crowding can be accomplished with a brail (a grating that covers the entire holding pool floor) or a grating wall that moves from one end of the pool to the other. Figure 2-46 shows an elevator design. Tank trucks for hauling adult fish vary significantly in size and complexity depending upon the trip length and number of fish being hauled. Tank volumes are typically 500 gallons to 2,000 gallons and include aeration equipment. Refrigerated units may also be necessary if long hauls are required or tank temperatures must be varied to match temperatures in liber- ation waters. The rule-of-thumb for tank sizing is one pound of fish per gallon of water. A greater vol- ume of water should be allowed for longer hauls or larger fish. f. Lock and Lift Systems. -A fish lock system is similar to a lock used for navigation. Fish are attracted or crowded into a lock chamber which is then closed. A valve is opened and water from the upstream reservoir fills the lock chamber. When the chamber is filled, a gate at the top is opened and the fish move from the lock chamber into the reservoir. The lock system is shown on figure 2-47. A fish lift or elevator system is shown on figure 2-48. It functions much the same way as the fish lock except the lock chamber is replaced by a mechanical lift system. 3. Selection of Upstream Fish Passage Fishways and traps accomplish the same objective, passing fish over barriers, with nearly the same cenainty of success. The decision is one of economics. If the barrier is of moder- ate height. say less than 50 feet. it is probably more economical to ladder it and perform routine maintenance. If the barrier is high, it may be more economical to construct a trap and operate it for the life of the project The resulting labor cost must then be less than the difference in capital costs between a fishway and a trap. a. Other Considerations. -The fish exit of the ladder should have a bar rack that has small enough spacing to prevent debris from entering the ladder but large enough spacing to allow safe upstream passage of fish. Usually a 9-inch spacing is large enough for most Nonh American species. It may be desirable to provide measures for the entry of some auxiliary water to the ladder. The quantity and location for the entrance of auxiliary water are described by Bell [1980]. Auxiliary water added to the ladder for attraction is usually through an intake separate from the exit that requires a bar rack of smaller spacing (typically 7/8-inch clear space); thus, preventing clogging debris from entering the system. Locations where auxiliary water enters the ladder must have a rack that will prevent the fish from entering the auxiliary water system. One-inch clear space is typical for these racks, though smaller species require smaller spacing. ASCE/EPRI Guides 1989 2-68 A 18 c D TRIJCIC LOADING CKJTE FlSH ELEVATOR Figure 2-46. -Elevator design. FISH LOCK POOL LENGTH POOL WIDTH WATER CEPTH CMIN) LOCK CHAMBER D ....... DAM • FILLING AND ATTRACTIOO WATER 8 12 4 6 3 3' 24 36 DISCHARGE VARIABLE (MIN) (CFS) 30 30 w.s. rJfFLOW 16 a' 3' M 30 Figure 2-47.-Fish lock system. [Hildebrand, 1981]. 2-69 ASCE/EPRI Guides 1989 Floods Mitigation and improvement Other design and construction considerations include the capability of the ladder to with- stand extreme floods. the foundation geology of the ladder itself, and the structural integri- ty of the dam or structure to which it will attach. In the construction phase of the project, provision should be made for dewatering the ladder site and, if necessary, for temporary passage. Run timing and weather can become critical factors in construction scheduling. I. INSTREAM F1SHERY MITIGATION AND HABITAT IMPROVEMENT 1. General lnstream enhancement is one form of mitigation that may be appropriate at some small- scale hydroelectric sites. Before selecting the methods to be used at any site, an interdisci- plinary team of project and agency engineers, fisheries biologists, and fluvial geomorphol- ogists should develop and approve clearly defined, measurable goals and a method for post-project monitoring to ensure the mitigation is effective. Some of the instream structures and methods developed to improve habitat diversity, trap spawning gravels, improve instream cover, and create aquatic insect production sites [Schnick et al., 1982; Anderson and Cameron, 1980; House, 1985, 1986; Hunt, 1969; Hassler, 1981, 1984; Finnigan, et al., 1980]. A POOL LENGTH B POOL WIDTH lc WATER DEPTH (MIN) 0 HOPPER SIZE (GAL) DISCHARGE VADIAAI J:;IM14XCFSJ .---, I I I I ATTRACTION WATER a' 121 4 6 3' 3' 250 500 30 30 Figure 2-48.-Fish lift system. [Hildebrand, 1981]. 161 8 3' 7!50 30 ASCE/EPRI Guides 1989 2-70 2. Structures and Methods a. Gabion Weirs. -Gabion weirs have been used extensively on the Pacific Coast to trap and retain spawning gravels, and to create pools for juvenile rearing, over wintering habitat and adult holding sites for anadromous fish [Cross, 1981; House, 1985]. The gabions are usually placed to form a "V" either facing upstream or downstream. Gabions built in series (two or more) are most effective. The distance between gabions depends upon stream gradient ranging from aoout 20 feet in steep to 30 to 40 feet in flatter gradients. To create usable plunge pools for rearing fish, the top of the downstream gabion must be level with the midpoint on the face of the upstream gabion. The center of each "V" shaped gabion structure should be placed in the center of the channel at the lowest point and the gabion wings should be installed at a 1 percent gradient from the mid-channel to bank. b. Boulders.-Large oouldersJarge enough to resist movement in most flood conditions, have been used by themselves or in clusters to create cover, rearing sites, and habitat diver- sity [Finnigan et al., 1980]. Some stability to small ooulder clusters can be established by chaining the individual ooulders to each other. Rocks greater than 454 kg and 1.6 meters in diameter will resist movement in current velocities up to 3 m/s. Four-foot rocks will be sta- ble in current velocities up to 4 m/s [DOT, 1979]. c. Half-Logs.-Cover deficiency can be improved by placing half-log structures [Hunt, 1969] at strategic points or anchoring downed trees to streambanks. Anchoring is accom- plished by cabling the tree or trees to deadmen or living trees along the bank. Downed trees have L , advantage of being esthetically pleasing and providing some bank protection while improving aquatic habitat diversity. d. Hewitt Ramp.-The Hewlitt Ramp (fig. 2-49) should basically be used in small, rela- tively stable streams with moderate gradients [DOT, 1969; Finnigan, et al., 1980]. The weir is normally submerged and log life expectancy is good (10 years). The ramp can provide cover in the form of hanging lip, plunge pool, and turbulence. e. Fish Stocking. -Frequently development of a small hydroelectric plant results in improved access for fishermen and increased fishing pressure on stocks that may not be able to sustain themselves under such conditions. In such cases, stocking of hatchery- reared fish from state, federal, or private sources can mitigate the impact of increased pres- sure. Concurrence from agencies charged with fish management should be sought and obtained prior to initiating such a program. The program will usually last the life of the project f. Counting Weirs. -On streams with spawning runs of fish, small hydroelectric develop- ment may provide an opportunity for constructing counting weirs and establishing baseline data on stocks of fish that would not otherwise be available. g. Cu"ent Deflectors. -Current deflectors have been used to create meandering patterns in straight stream channels and large scour holes and pools [DOT, 1979; Finnigan et al. 1980]. The deflectors may be constructed of rock, log cribs or gabions. The OOdy of the deflector should be embedded at least 0.6 meter below the stream channel and extend into Structures and methods Gab ion weirs Structures and methods 2-71 ASCE/EPRI Guides 1989 Side channels the bank 3 m beyond low water level. The streambed should be riprapped 4 to 6 meter s upstream and downstream from the structure. These concepts are illustrated on figures 2-50, 2-51, and 2-52. h. Side Channels. -Side channels, where water is shallow and water velocities low, are frequently important nursery areas for many species of fish. Conversions of ephemeral side channels to annual side channels can increase the year-round availability of nursery habitat if it has been identified as a limiting factor. A variety of methods can be used to divert additional water into ephemeral side channels including deflectors [Finnigan et al., 1980]. Dumped rock defklctor Figure 2-49.-Hewitt ramp. [DOT, 1979]. Figure 2-50. -Rock deftectors. [DOT, 1979]. e = 10 ft(3m) min. ASCEIEPRI Guides 1989 2-72 / / / / < / v (a} Deflects flow toward bank (b) Deflects flow .away from bank Figure 2-51.-EtTects of deflectors on stream flow. [DOT, 1979]. s Gablons Dimension L 9 s t 1 (gat1ions) f2 (rocks) b Common Limits 1/5 to I/2W 30o to goo W to lOW 2.5 to 3.0 ft(0.7to 0.9m) 3.0to 5.0ft(0.9 to 1.5m) 3 to 5 t2 Remarks Random spacing ot 2W to 5W performs very v.tell. Figure 2-52.-Dimensions for deflectors. [DOT, 1979}. 2-73 ASCEIEPRI Guides 1989 J. REFERENCES AISI (American Iron and Steel Institute), Handbook of Steel Drainage and Highway Construction Products, Washington, D.C., 1971. AISI, Modern Sewer Design, Washington, D.C., 1980. ASCE (American Society of Civil Engineers) Hydraulic Models, Manual of Engineering Practice No. 25, July 1942. ASCE, "Report of Task Force on Branching Conduits," Proceedings of the 21st Annual Hydraulics Division Specialty Conference, pp. 203-239, Bozeman, Montana, August 1973. ASCE/EPRI, Civil Engineering Guidelines for Planning and Designing Hydroelectric Projects (see front mat- ter for complete outline of all 5 volumes), 1989. AWWA (American Water Works Association) Concrete Pressure Pipe, Manual M9, 1979. Anderson, J.W. and Cameron, J.J., The Use ofGabions to Improve Aquatic Habitat, USBLM. Technical Note 342, 1980. Arthur, H.G. and Walker, J.J., "New Design Criteria for USBR Penstocks," Journal of the Power Division, ASCE, 96 (PO 1), 1970. Bates, D. W., Logan, 0., and Pesonen, E., "Efficiency Evaluation," Tracy Fish Collecting Facility, Central Valley Project, 1960. Bates, D.W., and Vanderwalker, J.G., "Exploratory Experiments on the Deflection of Juvenile Salmon by Means of Water and Air Jets," Fish Passage Research Program, U.S. Bureau of Commercial Fisheries, Seattle, Washington, September 1964. Barfield, B.J., Warner, R.C., and Haan, C.T., Applied Hydrology and Sedimentology for Disturbed Areas, Oklahoma Technical Press, Stillwater, Oklahoma, 1981. Bell, M.C., Fisheries Handbook of Engineering Requirements and Biological Data, Corps of Engineers, North Pacific Division, Portland, Oregon, 1980. Brater, E.F. and King, H.W., Handbook of Hydraulics, McGraw-Hill Book Co., New York, 1976. CDFG (California Department of Fish and Game), General Fish Screening Criteria, Sacramento, California, 1982. Chaudry, H .• "Applied Hydraulic Transients," Van Nostrand Reinhold Company, 1979. Chow, V.T., Open-Channel Hydraulics, McGraw-Hill Book Co., New York, 1959. Clay, C. H., Design of Fishways and Other Fish Facilities, 301 pp., Department of Fisheries of Canada, Ottawa, Ontario, Canada, 1961. COE (U.S. Army Corps of Engineers) Hydraulic Design of Flood Control Channels, EM-1110-2-1601, July, 1970. Cross, D., "Restoration of an Ephemeral Stream Dry Creek Tributary to the Kalmath River." Davis, C.V. and Sorensen, K.E .• Handbook of Applied Hydraulics, McGraw-Hill Book Co., New York, 1970. Dorratcague, D.E., Leidy, G.R., and Ott, R.E., "Fish Screens for Hydropower Developments," Water Power '85, Las Vegas, Nevada, September 25-27, 1985. DOT (U.S. Department of Transportation) Hydraulics of Bridge Watenvays, Washington, D.C., 1973. ASCE!EPRI Guides 1989 2-74 DOT, Restoration of Fish Habitat in Relocated Streams, FHWA-lP-7-3, Federal Highway Administration, 63 pp., 1979. Eberhardt, A., Penstock Codes-United States and Foreign Practice, Power Division, Specialty Conference, Electric Power Today and Tomorrow, ASCE, Denver, Colorado, 1965. EPRI (Electric Power Research Institute) Assessment of Downstream Migrant Fish Protection Technologies for Hydroelectric Application, Stone and Webster Engineering Cotp., Boston, MA, 1986. Eicher, G.J., "Fishways: Cost-Effective Alternatives" Hydro Review, pp. 84-88, Spring 1985a. Eicher, G.J., "Fish Passage-Protection of Downstream Migrants," Hydro Review, vol. IV, No.3, Falll985b. Parr, W.E., "Traveling Screens for Turbine Intakes of Hydroelectric Dams," Proceedings of Second Entrainment and Intake Screening Workshop, Johns Hopkins University, 1974. Finnigan, R.J., Marshall, D.E., Mundie, J.H., Slaney, P.A., and Taylor, G.D., Stream Enhancement Guide, 82 pp., Ministry of Environmental, Province of British Columbia, 1980. Fournier, P.W., "New Technology for Environmentally Safe, Money-Saving Water Withdrawal," Symposium on Surface Water Impoundments, Minneapolis, June 2-5, 1980. Giroud, J.P. and Frobel, R.K., "Geomembrane Products," Water Power and Dam Construction, March 1984. Gordon, J.L., "Vortices at Intakes," Water Power, April1970. Gordon, J.L., "Design Criteria for Exposed Hydro Penstocks," Canadian Journal of Civil Engineering, vol. 5, No.3, 1978. Gordon, J.L. and Murray, D.G., "Intake Design Concepts to Minimize Cost and Maximize Output," Hydro Review, vol. IV, No. 1, Spring 1985. Gulliver, J.S., Rindels, A.J., and Lindblom, K.C., "Guidelines for Intake Design Without Free Surface Vortices," Water Power and Dam Construction, 1983. Gulliver, J. and Wetzel, J., "Optimizing Design: Hydraulic Model Studies," Hydro Review, Fall, 1984. Gulliver, J.S., Rindels, A.J., and Lindblom, K.C., "Designing Intakes to Avoid Free Surface Vertices," Water Power and Dam Construction, September 1986. Hassler, T.J. (editor), Proceedings, Propagation, Enhancement, and Rehabilitation of Anadromous Salmonid Populations and Habitat Symposium, Humboldt State University, 162 pp., 1981. Hassler, T.J. (editor), Pacific Northwest Stream Habitat Management Workshop, Humboldt State University, 329 pp., 1984. Henderson, F.M., Open-Channel Flow, MacMillan Co., New York, 1966. Hildebrand, S.G. (editor), Analysis of Environmental Issues Related to Small-Scale Hydroelectric Development, II. "Design Considerations for Passing fish Upstream Around Dams," ORNL(fM-7396, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 1982. Hildebrand, S.G. (editor), Analysis of Environmental Issues Related to Small-Scale Hydroelectric Development, III. "Water Level fluctuation," ORNL(fM-7453, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 1980. House, R.A., "Evaluation of Instream Enhancement Structures for Salmonid Spawning and Rearing in a Coastal Oregon Stream," North American Journal of Fisheries Management, 5:2B, pp. 283-295, 1985. 2-75 ASCE/EPRI Guides 1989 House, R.A., "Effects of lnstream Structures on Salmonid Habitat and Populations in Tobe Creek, Oregon," North American Journal of Fisheries Management, 6: 1, pp. 38-46, 1986. Hunt, R.L., "Effects of Habitat Alternation on Production, Standing Crops and Yield of Brook Trout in Lawrence Creek, Wisconsin," Northcote, T.G., editor, Symposium on Salmon and Trout in Streams, University of British Columbia, 1969. EPA (U.S. Environmental Protection Agency) Development Document for Proposed Best Technology Available for Minimizing Adverse Environmental Impact of Cooling Water Intake Structures, Washington, D.C., December 1973. Hydraulic Research, "Charts for the Design of Channels and Pipes," Wallingford, England, 1983. Johnson, R.R. and McCormik, J.F., Strategies for Protection and Management of Floodplain Wetlands and Other Riparian Ecosystems, 1978. Leidy, G.R., and Ott, R.F., "Fish Screen Design: Selecting Fish Screens for Small Installations," Hydro Review, vol. V, No.2, Summer 1986. Lescovich, J.E., "Locating and Sizing Air Release Valves," AWWA Journal, July 1972. Lewitt, E.H., Hydraulics and Fluid Mechanics, Sir Isaac Putnam and Sons, Ltd., London, England, 1958. Logan, T.H., Prevention of Frazillce by Application of Heat, REC-ERC-74-15, USBR, 1974. Miller, D.S.,lnternal Flow Systems, British Hydromechanics Research Association, 1982. Monsonyi, E., Water Power Development, vol. I, "Low-Head Power Plants," Publishing House of the Hungarian Academy of Sciences, Budapest, Hungary, 1963. Moore, E.T., "Small Hydro Needs TLC," Hydro Review, vol. VII, No. II, April 1988. NMFS (National Marine Fisheries Services) Fish Screen Criteria, Environmental and Technical Services Division, Portland, Oregon, July 1982. Parmakian, J., Waterhammer Analyses, Dover Publications, Inc., New York, 1963. Pirok, J.N., "Some Problems of a Penstock Builder," Journal of the Power Division, ASCE, 83 (P03), 1957. Rainey, W.S., Considerations in the Design of Juvenile Bypass Systems, Proceedings of the Symposium on Small Hydropower and Fisheries, Aurora, Colorado, May 1-3, 1985. Rajaratnam, N., Katopodis, C., and Flint-Petersen, L., "Hydraulics of Two-Level Denil Fishway," J. Hydraulics Division, ASCE, New York, 1987. Rich, G., Hydraulic Transients, McGraw-Hill Book Co., New York, 1951. Richards, R.T., "New Ideas for Cylindrical Pipe Intakes Can Help Reduce Fish and Larvae Kills," Power Magazine, June 1980. Richards, R.T., and Hroncich, M.J., "Perforated-Pipe Water Intake for Fish Protection," Journal of the Hydraulics Division, ASCE, February 1976. Ruus, E., "Head Losses in Qosed Conduits," Seminar on Closed Conduit Flow, Fort Collins, Colorado, June 1980. Schnick, R.A., Morton, M.J., Mochalski, J.C., and Beall, J.T., Mitigation and Enhancement Techniques for the Upper Mississippi River System and Other Large River Systems, USFWS Resource Publication 149, 714 pp., 1982. ASCE/EPRI Guides 1989 2-76 Simons, D.B. and Senturk, F., Sediment Transport Technology, Water Resources Publications, Fon Collins, Colorado, 1979. Singh, B., Irrigation Engineering, New Chand and Bros., Roorkee,lndia, 1967. Streeter, V.L., Fluid Mechanics, McGraw-Hill Book Co., New York, 1971. Streeter, V.L. and Wylie, E.B., Hydraulic Transients, McGraw-Hill Book Co., New York, 1967. Taft, E.P., "Fish Passage: Fish Protection at Hydro Plants, Assessment of New and Old Technologies," Hydro Review, vol. V, No. 3, Fall 1986. USBR, (Bureau of Reclamation) Design of Small Canal Structures, Denver, Colorado, 1978. USBR, Design ofSmall Dams, 3rd ed., Denver, Colorado, 1987. Wagner, E.J., Report of the Winchester Power Project Assessment Team to the Director, Oregon Department of Fish and Wildlife, May 14, 1984. White, B.E., "Maintenance of Wood Stave Pipe in Hydroelectric Practice," Power Technical Magazine, vol. 60, No. 21, 1924. Zielinski, P.B., "Design for Elimination of Vonex Fonnation at lnlets," ASCE National Meeting on Water Resources Engineering, Los Angeles, California, January 21-25, 1974. Ziemer, G.L., Steep Pass Fishway Development, lnfonnational Leaflet No. 12, Alaska Department of Fish and Game, Division of Engineering and Services, Apri11962. 2-77 ASCEIEPRI Guides 1989 CHAPTER 3. POWER PLANTS CONTENTS Section Page A. Conceptual studies ...................................................................................................................................... 3-1 1. General .................................................................................................................................................... 3-1 2. Basic powerhouse infonnation ............................................................................................................... 3-1 3. Preliminary size ...................................................................................................................................... 3-1 B. Powerhouse types ........................................................................................................................................ 3-2 1. General .................................................................................................................................................... 3-2 2. 1'ypes ....................................................................................................................................................... 3-2 a. 1'ype A: surface ................................................................................................................................... 3-2 b. 1'ype B: underground and inground .................................................................................................... 3-2 c. 1'ype C: submersible ........................................................................................................................... 3-2 d. 1'ype D: others .................................................................................................................................... 3-2 3. l)escriptions of types .............................................................................................................................. 3-2 a. 1'ype A, subtype 1-integral intake indoor powerhouses ................................................................ 3-2 b. 1'ype A, subtype 2-integral intake semi-indoor (semi-outdoor) powerhouses ............................... 3-3 c. 1'ype A, subtype 3-integral intake outdoor powerhouses .............................................................. 3-3 d. 1'ype A, subtype 4-horizontal unit powerhouses ........................................................................... 3-3 e. 1'ype A, subtype 5-surface powerhouses at dam ............................................................................ 3-3 f. 1'ype A, subtype 6-detached surface powerhouses ........................................................................ 3-8 g. 1'ype B, subtype 1-underground powerhouses ............................................................................... 3-8 h. 1'ype B, subtype 2-inground powerhouses ..................................................................................... 3-8 i. 1'ype C -submersible powerhouses ................................................................................................. 3-8 j. 1'ype 0---others ................................................................................................................................. 3-8 C. Selecting the powerhouse type ................................................................................................................ 3-19 1. General .................................................................................................................................................. 3-19 2. Powerhouse type related to conduit length, head developed, and proximity to the dam ...................... 3-19 a. Low heads ......................................................................................................................................... 3-19 b. Intennediate heads ............................................................................................................................ 3-19 c. High heads ......................................................................................................................................... 3-20 3. Powerhouse type affected by topographic constraints .......................................................................... 3-20 4. Geologic constraints .............................................................................................................................. 3-20 5. Constraints dictated by high tailwater ................................................................................................... 3-20 6. Other constraints ................................................................................................................................... 3-20 D. Powerhouse size ....................................................................................................................................... 3-21 E. Superstructure ........................................................................................................................................... 3-21 1. General .................................................................................................................................................. 3-21 2. Sizing ..................................................................................................................................................... 3-21 3. Erection bay and service area ................................................................................................................ 3-22 F. Substructure arrangement .......................................................................................................................... 3-22 1. General .................................................................................................................................................. 3-22 2. l)esign requirements .............................................................................................................................. 3-22 3. Substructure components ...................................................................................................................... 3-23 ASCE/EPRI Guides 1989 CONTENTS -Continued Section Page a. Water passage ........................................................................................................................................ 3-23 b. Draft tube .............................................................................................................................................. 3-24 G. Thrbine setting .......................................................................................................................................... 3-24 H. Excavation ................................................................................................................................................ 3-28 1. General .................................................................................................................................................. 3-28 2. Excavation requirements ....................................................................................................................... 3-28 a. Vertical units ..................................................................................................................................... 3-28 b. Horizontal units ................................................................................................................................. 3-28 3. Other factors affecting excavation ........................................................................................................ 3-28 a. Foundation material .......................................................................................................................... 3-28 b. Thrbine setting .................................................................................................................................. 3-28 I. Structural requirements and analysis ......................................................................................................... 3-28 1. Structural fra.tne ..................................................................................................................................... 3-28 2. Specifications ........................................................................................................................................ 3-29 a. Concrete ............................................................................................................................................ 3-29 b. Reinforcing stee1. .............................................................................................................................. 3-29 c. Structural steel .................................................................................................................................. 3-29 d. Bolts used in structural joints ........................................................................................................... 3-29 e. Anchor bolts ..................................................................................................................................... 3-30 f. Welds ........................................................................................................................... ; .................... 3-30 g. Rock bolts ......................................................................................................................................... 3-30 3. Design loads .......................................................................................................................................... 3-30 a. Load combinations for steel members ................ _ ............................................................................ 3-30 b. Load combinations for concrete members ....................................................................................... 3-30 c. Seismic loads ..................................................................................................................................... 3-31 d. Lateral earth pressures ...................................................................................................................... 3-31 J. Structural stability requirements ................................................................................................................ 3-31 1. Loading conditions ................................................................................................................................ 3-31 2. Soft foundations .................................................................................................................................... 3-32 3. Uplift ..................................................................................................................................................... 3-33 K. Hydraulic requirements ............................................................................................................................ 3-33 1. High water levels ................................................................................................................................... 3-33 2. Seepage and drainage ............................................................................................................................ 3-33 L. Powerhouse equipment ............................................................................................................................. 3-34 1. General .................................................................................................................................................. 3-34 a. Station diagra.tn ................................................................................................................................. 3-34 2. Turbines ................................................................................................................................................. 3-35 a. General .............................................................................................................................................. 3-35 b. 1'ypes ................................................................................................................................................. 3-35 c. Thrbine selection ............................................................................................................................... 3-40 3. Generator gear box ................................................................................................................................ 3-55 a. General .............................................................................................................................................. 3-55 b. 1'ypes and arrangements .................................................................................................................... 3-55 c. Efficiency ......................................................................................................................................... 3-55 ASCE/EPRI Guides 1989 ii CONTENTS-Continued Section Page 4. Generators ............................................................................................................................................. 3--55 a. General .............................................................................................................................................. 3--55 b. Synchronous generators .................................................................................................................... 3--55 c. Induction generators .......................................................................................................................... 3--55 d. Generator voltage .............................................................................................................................. 3--56 e. Excitation .......................................................................................................................................... 3--56 5. Hydraulic power unit. ............................................................................................................................ 3--56 6. Control equipment ................................................................................................................................. 3--56 a. Govemors .......................................................................................................................................... 3--56 b. Plant operation .................................................................................................................................. 3--57 c. Headwater and tail water measurement devices ................................................................................ 3-57 M. Auxiliary electric equipment .................................................................................................................... 3--58 1. Switchgear ........................................................................................................................................... 3--58 2. Station service transformer ................................................................................................................. 3--59 3. Motor control center ............................................................................................................................ 3--59 4. Distribution panel ................................................................................................................................ 3--59 5. OC control power supply .................................................................................................................... 3--59 6. Grounding system ............................................................................................................................... 3--60 7. Lighting ............................................................................................................................................... 3--60 8. Security ............................................................................................................................................... 3--60 9. Lightning protection ............................................................................................................................ 3--61 10. Raceways (conduit and cable trays) .................................................................................................... 3--61 11. Wires and cables .................................................................................................................................. 3--61 12. Auxiliary power .................................................................................................................................. 3--62 N. Auxiliary mechanical equipment .............................................................................................................. 3-62 1. r>ewatering system and station sump .................................................................................................... 3--62 a. Dewatering systems .......................................................................................................................... 3--62 b. Station sump ..................................................................................................................................... 3--62 2. Cooling water system ............................................................................................................................ 3--62 3. Fire protection ....................................................................................................................................... 3--63 4. Eyewash ................................................................................................................... , ............................ 3-63 5. Heating, ventilating, and air conditioning ............................................................................................. 3--63 6. Gates and valves .................................................................................................................................... 3--63 a. Tumine shutoff valves ....................................................................................................................... 3--63 b. Intake gates ....................................................................................................................................... 3--64 c. Draft tube gates ................................................................................................................................. 3--64 d. Stoplogs ............................................................................................................................................ 3--64 e. Bypass valves .................................................................................................................................... 3--64 7. Cranes/equipment handling ................................................................................................................... 3--64 a. Powerhouse ....................................................................................................................................... 3--64 b. Intake deck ........................................................................................................................................ 3--64 c. Draft tube deck ................................................................................................................................. 3--64 8. Piezometer system ................................................................................................................................. 3--69 9. Plant elevator ......................................................................................................................................... 3--69 iii ASCE/EPRI Guides 1989 CONTENTS -Continued Section Page 0. Esthetics .................................................................................................................................................... 3-69 1. Powerhouse appearance ........................................................................................................................ 3-69 2. Painting ................................................................................................................................................. 3-69 3. Noise ..................................................................................................................................................... 3-71 P. References .................................................................................................................................................. 3-71 FIGURES Figure 3-1 Powerhouse type A, subtype 1-integral intake indoor installation .................................................... 3-3 3-1 Powerhouse type A, subtype 2-integral intake indoor installation .................................................... 3--4 3-3 Powerhouse type A, subtype 3-integral intake semi-indoor (semi-outdoor) installation .................. 3-5 3--4 Powerhouse type A, subtype 3-integral intake outdoor installation .................................................. 3-6 3-5 Powerhouse type A, subtype 4-horizontal unit .................................................................................. 3-7 3-6 Powerhouse type A, subtype 5-surface powerhouse at dam .............................................................. 3-9 3-7 Powerhouse type A, subtype 6-detached surface ............................................................................. 3--10 3-8 Powerhouse type A, subtype 6-canal and penstock ......................................................................... 3--11 3-9 Siphon penstock .................................................................................................................................... 3--12 3--10 Section through submersible powerhouse (pit turbine) ........................................................................ 3-13 3-11 Inverted flow system ............................................................................................................................. 3-15 3-12 Underground PRV energy-recovery station .......................................................................................... 3-15 3-13 Aboveground PRV energy-recovery station ......................................................................................... 3-16 3-14 Inpipe turbine ........................................................................................................................................ 3--16 3-15 Retrofit installation -existing dam with undersluice ......................................................................... 3-17 3-16 Retrofit installation -modified dam ................................................................................................... 3--18 3-17 Submersible turbine .............................................................................................................................. 3-19 3-18 1'ypical draft tube shapes ...................................................................................................................... 3--25 3-19 Draft tube layout (pit type) ................................................................................................................... 3--26 3-20 Chart of recommended heights of hydraulic turbine settings ............................................................... 3-27 3-21 Typical single-unit station single-line diagram ..................................................................................... 3--35 3-22 Principles of operation of impulse turbines .......................................................................................... 3--36 3-23 Reaction and cross-flow turbines .......................................................................................................... 3-38 3-24 Turbine application chart ...................................................................................................................... 3-39 3-25 Application ranges for turbines and pumps as turbines ........................................................................ 3--40 3-26 Effect of load change on efficiency for hydraulic turbines ................................................................... 3--41 3-27 Typical peak efficiencies of various turbines in relation to specific speed ........................................... 3--42 3-28 Approximate recommended specific speed for hydraulic turbines ...................................................... 3--44 3--29 Performance characteristics-pump as turbine .................................................................................. 3--46 3-30 Powerhouse layout-horizontal Francis turbine ................................................................................. 3--48 3-31 Powerhouse layout-vertical Francis turbine ..................................................................................... 3--49 3-32 Powerhouse layout-open flume turbine ........................................................................................... 3--50 3--33 Powerhouse layout-propeller turbine with headworks ..................................................................... 3--51 3-34 Powerhouse layout-tubular turbine with penstock ........................................................................... 3--52 ASCE/EPRI Guides 1989 iv CONTENTS -Continued Figure Page 3-35 Powerhouse layout-bulb turbine with head works ............................................................................ 3-53 3-36 Powerhouse layout-cross-flow turbine ............................................................................................. 3-54 3-37 Simplified schematic diagram of governor system ............................................................................... 3-58 3-38 Turbine shutoff valves .......................................................................................................................... 3-65 3-39 Intake wheeled gates ............................................................................................................................. 3-65 3-40 Stoplogs ................................................................................................................................................ 3-66 3-41 Fixed cone valve ................................................................................................................................... 3-66 3-42 Material handling equipment ................................................................................................................ 3-67 3-43 'I'ypical portable jib crane ..................................................................................................................... 3-68 3-44 Intake gantry crane ................................................................................................................................ 3-68 3-45 Draft tube monoraiL .............................................................................................................................. 3-70 This chapter was written by: Ashok K. Rajpal, P.E. Vice-Chainnan Mead and Hunt, Inc. 6501 Watts Rd., Suite 101 Madison, Wisconsin 53719-1361 CREDITS v ASCE/EPRI Guides 1989 CHAPTER 3. POWER PLANTS A. CONCEPTUAL STUDIES 1. General A powerbouse is the heart of any hydroelectric project. It provides the necessary waterway General for the operation of power-generating equipment (turbine) and houses the generator and control equipment. The powerhouse generally has two components: a substructure or foun- dation and a superstructure. The size of the powerbouse differs from one project to another depending upon its power-generating capacity, topography, and the geographic location of the project. Remote sites may require provisions for storage of additional equipment, spare parts, and space for repair and maintenance. The climatic conditions must also be consid- ered in the design of the structure. 2. Basic Powerhouse Information The topography of the site dictates the physical configuration of the powerbouse. For small projects surface powerbouses are built to minimize the cost of construction or inground powerhouses are built to minimize visual impact. To determine feasible layout for a power plant, the following information should be devel- oped: • Number and capacity of generating units (see sec. L.2.c) • Powerbouse (turbine) setting with respect to tailwater (see sec. G) • 1)'pe of powerhouse suitable for the existing topographic, geologic, and environmen- tal conditions The types of powerhouses are described in section B. 3. Preliminary Size For feasibility studies, preliminary sizing of the powerllouse can be quickly determined on the basis of similar existing projects. Such information is sufficiently accurate when trans- ferred to the small-scale topographic maps used for studies. The following steps are then followed to adapt for site specifics: • Zero-in on the powerhouse type • Firm up setting with respect to tailwater • Develop arrangement and dimensions of water passages • Develop powerbouse concrete outline • Incorporate the above into overall project concept studies Basic information Preliminary size 3--1 ASCEIEPRI Guides 1989 Powerhouse types Types Surface Underground/ in ground Submersible B. POWERHOUSE TYPES 1. General Selection of the powerhouse type and configuration is governed by the following consider- ations: • Water conduit length and profile • Head developed at the project • Powerhouse proximity to the dam • Topographic and access constraints • Geologic constraints • Exposure to elements • 100-year or PMF (probable maximum flood) water levels • High and low tail water elevations • Type of turbine and generator • Project-specific constraints 2. Types Powerhouses for hydroelectric projects can be classified into the types listed below. a. Type A: Surface • Indoor type: All equipment is located inside the building. • Semi-indoor type: The turbine/generator units are individually weatherproofed and located outside, whereas the controls are located inside. • Outdoor type: Most of the equipment is located outside. b. Type B: Underground and Inground.-Underground powerhouses are rarely used for small hydro projects; however, in some cases a pit type powerhouse is considered because of access problems and high tail water at flood stages. c. Type C: Submersible.-During high river flows, the water levels may become higher than the structure. d. Type D: Others. -Innovative layouts and design. 3. Descriptions of Types a. Type A, Subtype 1 -Integra/Intake Indoor Powerhouses. -The powerhouse-intake forms a part of the dam (water retaining structure) and is constructed integrally with the generating bay to form the powerhouse (fig. 3-1 ). This layout is suitable for low-head installations. As an alternative, to economize the service crane is eliminated from the powerhouse and accessways are provided through the roof. Installation of equipment and repairs are made through these removable hatches by mobile crane (fig. 3-2). ASCEIEPRI Guides 1989 3-2 OPEN FLUM£ TURBIN£ Figure 3-1.-Powerhouse type A, subtype 1-integral intake indoor installation. Medium-now, low-head, deep turbine setting. [CEA, 1983]. Generally, powerbouses are founded on competent rock; however, bearing piles can be used to support the structure. b. Type A, Subtype 2 -Integral Intake Semi-Indoor (Semi-Outdoor) Powerhouses. These powerbouses are similar to subtype 1 powerbouses, except that only the switchgear and control equipment is enclosed for weather protection (fig. 3-3). c. Type A, Subtype 3 -Integral Intake Outdoor Powerhouses. -An integral-intake outdoor powerllouse is just an extension of the semi-indoor subtype with the superstructure enclosure removed. Typical examples are shown on figure 3-4. Outdoor facilities are eco- nomical and are used for small low-head installations. d. Type A, Subtype 4-Horizontal Unit Powerhouses. -Powerbouses with horizontal units have become more popular in the past few decades for the lower head ranges (up to 50 ft) of run-of-river projects. lbese are most suitable for large flows and low heads. The layout is similar to semi-indoor subtype. Examples are shown on figure 3-5. e. Type A, Subtype 5-Surface Powerhouses at Dam. -This subtype of powerbouse is used when the head becomes too high for integral-intake powerhouses; i.e. for medium- and high-head projects and when the river channel is wide enough to accommodate the length of the powerhouse. Integral intake semi-indoor (semi-outdoor) Outdoor Horizontal unit Surface Powerhouse at dam 3-3 ASCEJEPRI Guides 1989 R!"MOVABLE HATCH a. Francis turbine. REMOVABLE HATCH b. Propeller turbine. Figure 3-2. -Powerhouse type A, subtype 2 -integral intake indoor installation. ASCE/EPRI Guides 1989 3-4 ~ > j 0 c:: .... 0. n (II ..... \0 00 \0 !Jl:BWAUJt,_ MOVABLE CRANE (OPTIONAL) ·•. ·~ ... ENCLOSURE fOR ElECTRICAL CONTROLS . . ,· "''. ' ft -,<.~l~~-~ ~~ -l~" Figure J-.3.-Powerhouse type A, subtype 3-integral intake semi-indoor (semi-outdoor) installation. St. Anthony Falls, Minnesota. a. Siphon penstock with pump as turbine. POWER TR.t.INS OR SPEED INCREASER b. Siphon penstock. fVRBINE STE£1... CASING OF A VERTICAL PUMP Figure 3-4.-Powerhouse type A, subtype 3-integral intake outdoor installation. [CEA, 1983]. ASCE/EPRI Guides 1989 3--6 rREMOVABL£ HATCH a. Thbe turbine, medium flow, medium head. b. Bulb turbine, large flow, low head. Figure 3-S.-Powerhouse type A, subtype 4-horizontal unit. Type A, subtype 5 powerhouses may be constructed at the toe of the dam with short water conduits. Access to such a powerhouse and finding a suitable powerhouse foundation in a deep river gorge may offset the savings in conduit length, and other powerhouse locations may be economically more advantageous. These types of powerhouses are also suitable for use at existing canals and at existing dams with existing outlet sluice or low level outlet for flood control. An example is shown on figure 3-6. 3-7 ASCE/EPRI Guides 1989 Detached powerhouse Underground powerhouse In ground powerhouse Submersible powerhouse Other powerhouse types Example f. Type A, Subtype 6-Detached Surface Powerhouses. It is not always feasible (as dis- cussed in more detail in Section C, "Powerhouse Layout''), to make the powerbouse part of the reservoir retaining structure (integral-intake powerbouses), nor to locate it at the toe of the dam or in the dam itself. In such cases, the surface powerbouses are detached from the main dam and are located either in the stream or on river banks downstream of the dam. Free-standing steel penstocks or open charmels convey the water between the intakes and the detached powerhouses. Figures 3-7 and 3-8 illustrate examples of detached power- house designs. On figure 3-8, the water is diverted through a power canal or headrace charmel to the site of the headworks located near the powerhouse, with a minimum of head loss. Penstock(s) further convey the water down to the powerbouse from the headworics. Another example of this type is a powerbouse built at an existing dam where the dam structure may not be disturbed to construct an intake. In such cases, the water can be lifted above the crest of the dam by a siphon penstock and conveyed to the powerbouse located away from the dam (fig. 3-9). The lifting of water above the crest of the dam is limited to approximately 25 feet because of the practical vacuum limit g. Type B, Subtype 1 -Underground Powerhouses. -As its name implies, the entire powerbouse structure is located below the ground surface in an excavated cavity. Water is conveyed by a penstock or tunnel to the powerhouse. This type is normally used for large conventional projects and is seldom economical for small hydro projects. For details, refer to the guidelines for conventional hydro plants. h. Type B, Subtype 2 -Inground Powerhouses.-Most of the inground powerbouse and all of its foundation are built below grade level to provide adequate submergence for the turbine runner. In many instances the grade level may be high and the entire power- house could be built below grade. Access in that case is provided from the roof level. L Type C-Submersib~ Powerhouses.-Submersible powerhouses are good for low- head development at existing dams or instream locations. 1be powerhouse structure is water- tight and has a low profile such that during high flows, the water can flow over the structure, thus not reducing the spillway capacity. The access to the powerhouse is through a conical tower (like a submarine) or through a watertight door (see fig. 3-10). Large watertight hatch- es are provided in the roof of the powerbouse for maintenance of equipment. Horizontal units like tube-, bulb-, or pit-type turbines are generally used for these installations. j. TypeD-Others.-Many innovative designs have been developed for small-head (between 5 and 12 ft) developments. The important aspects of all these developments are simplicity of component parts and low operating and maintenance costs. One such scheme, which has been successfully constructed, is called "Inverted Aow Concrete-Built Siphon System." Figure 3-11 illustrates one such installation. The other situations where nonconventional powerbouses are coming into common use are (1) in energy recovery stations in connection with pressure reducing valves; (2) in areas where reversible submersible pumps are used inside pipe systems; and (3) in floating pow- erbouses (not discussed in the Guidelines). ASCEIEPRI Guides 1989 3-8 CANAL OR OAM W/NEW PENSTOCK CONCRETE OAM WI EXISTING CONDUIT EARTH DAM WI EXISTING OUTLET WORKS Figure 3-6. -Powerhouse type A, subtype 5 -surface powerhouse at dam. 3-9 ASCE/EPRI Guides 1989 I ... : Roadway-(11077~ .. • ~~· Penstoells '"' - ··£1 ~860 ~;:::::::~g..-1.- a. Section through darn and powerhouse. Shasta Darn, California. '"Grout·curtcill • 10 .. b. Forebay and powerhouse section. Parker Darn, Arizona. Figure 3-7. -Powerhouse type A, subtype 6 -detached surface. ASCE!EPRI Guides 1989 3-10 RIGHT CONCRETE NON·OVERFLOW DAM CONCRETE WALKWAY Z.4 KV LOCAL OISTRieUTION UNE SPILLWAY 10' OIA. PENSTOCK CHAIN-LINK FENCE - 0 X> < ,., R.R. BRIDGE Figure 3-8. -Powerhouse type A, subtype 6-canal and penstock. Plan views. Hatneld Hydro Project, Wisconsin. 3-11 ASCEIEPRI Guides 1989 > i ~ ~ en -\0 ~ r -tv HEADWATER : Summer Normal El. 1312 Winter low--El. 1297 Apex El. 1322.5 lnlake With Trash Reck Dock Concrete 2 -9' Diameter Penstocks I II I I TAILWATER : Summer Normal --El. 1280. Winter low--El. 1278 Vacuum Header 1297 II 1\_ \__Apex Invert 1 El. 1313.5 ' l Core Wall Figure 3-9.-Siphon penstock. Conventional turbine-generator system. Chippewa Reservoir Dam, Wisconsin. [Rajpal, 1987]. lf -w ~ ~ 0 c:: ~ -\0 ~ LOW -~~r 1.90 t------------·· 0:100 TAILWATER -;=:......-==;;:;:;=-n-~ .!!!QU~!,YtA.Hft. L~~~?T~$;if~\;l~c -L·--50 PENTHOUSE 'fD \_ flUNN~R O:IQQ~~~~ QIOO _l!~ AOIIIhl!R LOW HEAOWAHR ---rr - l!.!> 0 Figure 3-10.-Section through submersible powerhouse (pit turbine). Allegheny Lock and Dam No. S. Pressure reducing stations Submersible pumps Energy recovery stations are usually associated with pressure-reducing stations on munici- pal water supplies. There, pressure is reduced from 200 to 400 lbJin2 down to 60 to 100 lb/in2 by means of pressure reducing valves (PRVs). These PRVs are located in vaults under highways, airport runways, etc., so space is very limited. Turbines can be placed in series or in parallel with the PRVs. Because constant flow and pressure are so important in municipal systems, the PRV must be able to be activated instantly in case of a turbine outage without creating a flow blockage or a pressure surge. Careful analysis must be given to the surge hydraulics, turbine and PRV characteristics, and the electrical and mechanical linkage between the PRV and turbine. A typical turbine/PRY layout is shown on figure 3-12. In PRV systems, the upstream and downstream flow and pressure requirements, and thus the effective head, can vary radically with the season of the year. Because PRV vaults are usually located underground in urban areas, space is at a premium. Therefore, the size of the unit is a consideration. Isolation valves must be added so that the turbine may be ser- viced without interrupting the water system. Reversible pumps are usually the most cost- effective in the above situations. New versions have specially designed impellers and/or wicket gates to improve efficiency. Space requirements may also dictate installing the electrical gear at street level, although the turbines and PRV are underground. A total above ground energy-recovery station is shown on figure 3-13. In this case, the turbine is used in conjunction with pumps, which is a common occurrence in larger stations near reservoirs. In this case, the integration of the turbine and pump electrical systems is a major effort. Submersible pumps in small hydropower plants up to 500 kW are effective in areas where the turbine and generator must be completely submerged. They provide a low-cost means of retrofit installation in old dams, installation in siphons, or installations in existing pipelines. Several configurations are shown on figures 3-14 , 3-15, and 3-16. In each case, the electronic controls are located outside the pipe in a high and dry area. Figure 3-17 shows the advantage of this feature. In this case, the submersible pumps were retrofit on an old dam that would be overtopped in a 25-year or greater flood event. Thrbines are encased in heavy-wall pipelines for flood protection while the switchgear and controls are located alx>ve the 100-year floodplain. New impeller designs with movable blades and wicket gates have made these units more versatile and efficient. ASCE/EPRI Guides 1989 3-14 CONTROLS -----\ --\ Figure 3-11.-Inverted flow system. [Bourgeacq, 1983]. TO 24' DIAMETER MAIN IN EUCUO -AV. 30'-0' PLAN _._"'"=or-ISOLATION VALVES WITH HYDRAULIC OPERATORS Figure 3-12.-Underground PRV energy-recovery station. 3-15 ASCEIEPRI Guides 1989 ll£-IN TO £.X15l1MC 4 I • SUPPLY LIM( ( ""•o·l ..fQ.WEBHOU§E PlAN TI(-IH TO 12.5 KYA POWER liH( ( ... 1oo·) CONfff:C llHC PIP( TO RESERVOIII (OG£ OF TAILRACE (fLOW CHAW8ER) 8£LOW Figure 3-13.-Aboveground PRV energy-recovery station. PRESSURE CONTROLLED BYPASS VALVE VALVE ASCEIEPRI Guides 1989 COOLING WATER FLOW RECTIFIER DRAFT TUBE TURBINE- GENERATOR Figure 3-14. -Inpipe turbine. ~16 VALVE 'f ...... -..l > i 22 Q c ~ CA ...... \0 ~ H.\J. el ... 516,o ~4'X1Sr/~ ~~~ ~-,......," fL-1 12:rv I { 1 1 k _____. ~ '---L ;:--"T ELBOW Dli!,P'T TUB£ Figure 3-15.-Retrofit installation-existing dam with undersluice. > (I) ~ E/.lft] ;8 ....... Q /'tO c: ~ ~ ...... \0 00 \0 /J5 t I 130 OS r ...... 00 120 /15 //0 • -~l[_JJ .SLJOE{$ArE ·• • • . ~~oj;: • • • I .S.VBHER.SI.S.t.E--- PUMP r.v,e/!1/A.IE VALl/£ .5r&:H PowFR CABLE ~ REHOPdBLE Cova.Ji!' PIPE .MA)t. T.W. /.?.3.5 --=:::::::: ~~---==---=-===-- ~TU::..!!..~~-- ... '"-:-1.1 1 •• -~~ Figure 3-16.-Retrofit installation -modified dam. !JI,.....,.~:T L -~...-PAM~~:::= G4P -0~·~~ "n:>t"' QF ~ ~EAM E.Le.Va:TlO~ 1'-ZO' t t Figure 3-17.-Submersible turbine. C. SELECTING THE POWERHOUSE TYPE 1. General 1be selection of powemouse type depends on site-specific conditions; economy is always a primary concern. 1be following discussions, along with examination of the actual site con- ditions and the geologic and hydrologic information available for conceptual studies of the project, serve as a guide for selecting the most suitable type powerllouse. 2. Powerhouse l)pe Related to Conduit Length, Head Developed, and Proximity to the Dam The length of the water conduit between the reservoir and the powerhouse, or the length of the tailrace, constitutes one of the primary economic considerations in conceptual studies of the power plants. The water conduit length depends greatly on the head developed at the project, on the type of dam selected, and on the powerhouse type itself. For the sake of economy, the water passage connecting the reservoir with the powerhouse should be as short as possible. a. Low heads. -For low-head (less than 30 ft) run-of-river plants, the shortest conduit length is obtained by providing an integral intake with water passages as the upstream part of a conventional surface powerhouse. Such a powerhouse constitutes a part of the dam to retain the reservoir (figs. 3-1 through 3--4). b.Intermedillte heads.-For intermediate heads (less than 130ft), integral intake designs prove structurally difficult, and the intake is incorporated in the dam or provided as a sepa- rate structure nearby, and the powerhouse becomes a separate structure located as close to the dam as is structurally safe to reduce the length of the connecting conduits (fig. 3-5). Powerhouse layout General Powerhouse affected by conduit length Low head Intermediate head 3-19 ASCF,JEPRI Guides 1989 High head Topographic constraints Geologic constraints Other constraints The powerhouse may also be located within a gravity or hollow gravity dam. c. High hetuls.-For high-head installations (greater than 130ft), various alternatives for powerhouse locations may exist, again depending on the type of dam used, prevailing topography, geologic conditions, power intake location with related constraints for water conduit arrangement, and connection to the powerhouse 3. Powerhouse l)pe Affected by Topographic Constraints To obtain the best flow conditions, the powerhouse should be set nonnal to and in the stream utilized for power development. Narrow valleys, with high and steep banks may dictate other setting arrangements or differ- ent powerhouse types altogether. Surface powerhouses, with several units, may have to be located along the river banks, dictating longer conduits. High, steep banks may result in expensive excavations with high cut slopes, which may present stability problems with commensurate increase in construction and maintenance costs. This alternative may not be economical for a small hydro facility. 4. Geologic Constraints It is a generally accepted practice to found powerhouses on sound rock. All powerhouses of the Tennessee Valley Authority have been built on rock foundations. However, some powerhouses have been built on sand foundations. Petenwell and Castle Rock on the Wisconsin River in Wisconsin and the Sam Rayburn Power Plant on the Angelina River in Texas are some examples. Alternately, piles may have to be utilized to take the load of powerhouse. Refer to the Conventional Hydro Guidelines for design considerations. S. Constraints Dictated by High Tailwater High tailwater conditions may rule out indoor surface powerhouses because the access to such powerhouses would be at a commensurately higher level. requiring a higher overall powerhouse structure. A semi-indoor powerhouse, with access at roof level and superstructure designed to protect against higher tailwater levels, will result in a more economical design than an indoor powerhouse. The powerhouse can be made watertight, if necessary, to allow high water to flow over the structure. This aspect is covered earlier in subsection 2.c above. 6. Other Constraints Other possible constraints in the selection of powerhouse type include the following: • Existing dam cannot be disturbed to construct intake • Existing structures • Proximity to existing transmission lines ASCEIEPRI Guides 1989 3-20 • Difficult and expensive surface access in narrow canyons with steep walls • Encroachment on railroad or highway right-of-way • Oimate • Archaeological aspects • Environmental considerations • Socio-demographic aspects The last three constraints in the above list would most likely be treated in the overall siting studies and, therefore, may not affect the selection of the powerhouse type. D. POWERHOUSE SIZE The layout of the unit, the functions of the type of equipment selected, the diameter of tur-Powerhouse bine runner, and the turbine manufacturer's draft tube configuration detennine the power-size house width and length. The selection and sizing of turbines are discussed in section L. Once the size of the turbine is known, the preliminary layout can be made based on guide- lines presented in the following sections. The final bay size and layout should be deter- mined after consultation with the turbine manufacturer and other suppliers of auxiliary equipment. E. SUPERSTRUCTURE Super- structure 1. General The primary purpose of the powerhouse superstructure is to protect the machinery from General weather and vandalism. It also provides a shelter for operators and facilities for the repair and maintenance of the equipment The superstructure can be built using one or a combina- tion of materials. Masonry or concrete buildings are generally expensive but resistant to vandalism. They can be used in both cold and hot climates because they provide good cli- mate control. Prefabricated concrete or steel structures are also commonly used. A wood- frame structure is inexpensive but more vulnerable to fire and vandalism. Regardless of the materials used, the design must allow for live loads imposed by hoist or other lifting equip- ment during and after construction. 2. Sizing The size of the superstructure depends on the type of turbine-generator equipment selected. Sizing Each piece of equipment should be located so that easy access is provided for maintenance and removal of parts. The height of the fully enclosed superstructure should be such that a traveling crane (if provided) will be able to handle the largest piece of equipment and carry it over the other machinery while in operation. If any headgates located within the power- house are operated by a crane, they may govern the height. A crane or monorail in the powerhouse is generally desirable because it will facilitate Crane maintenance, but it is not necessary. A removable roof can be provided over the requirement turbine-generator and, if needed, a mobile crane can be used to lift these out of the building for necessary repairs. This approach may be more suitable for small hydro projects, where the initial cost is critical. In such cases, it is desirable to provide small-capacity (say 2,000 3-21 ASCEJEPRI Guides 1989 Location of generator floor Erection bay service area Substructure General Design requirements to 4,000 lb) monorails at strategic locations for routine maintenance wort.. Portable, knock- down gantry cranes on wheels are available to 10 tons. The generator operating floor of the powerhouse is nonnally located above the level of the project design flood to protect the equipment. Alternatively, the building can be made floodproof. Low-profile horizontal turbines are often a practical selection for a site where flood-proofing is required, such as shown on figure 3-10. In any case, switch gear and con- trol equipment must be located above the tail water elevation. In some cases, small-capacity units can be installed outdoors on a simple foundation base. The turbine is enclosed in a tube and the generator is mounted outside the tube. The control equipment is located in a nearby enclosure. This is suitable for small installations such as shown on figure 3-4. In addition to space required for turbine-generator units, certain space is required for office, switchgear, controls, auxiliary equipment, storage, maintenance, assembly, and dis- assembly of major generating equipment. The amount of space required is a function of the size and location of the project 3. Erection Bay and Service Area A large erection and service area inside the powerhouse, though beneficial in some ways, increases the cost of powerhouse. A large area may be advisable for storage of spare parts and special tools and a small maintenance workshop if the powerhouse is located in a remote area with adverse weather conditions. However, a maintenance and laydown area large enough to handle the largest equipment, in addition to the area required for control equipment, is desirable. In low-cost, small hydro plants, large hatches are sometimes pro- vided in the roof of the powerhouse to enable the large pieces of the turbine-generator to be taken out for service and repair. This reduces the requirement for an erection and main- tenance area and eliminates a costly and heavy powerhouse crane. All maintenance and erection wort. is accomplished with the help of mobile cranes. F. SUBSTRUCTURE ARRANGEMENT 1. General The substructure supports the equipment and provides the necessary water passage. Depending upon the location of the powerhouse, the substructure may fonn an integral part of the dam (figs. 3-1 through 3-4) or it may be located remote from the dam (figs. 3-5, 3-6, and 3-7), with the dam and the intake being separate structures. When the substructure is an integral part of the dam, it acts as a part of the water retaining structure and, therefore, must be designed as a dam. 2. Design Requirements The structural design of the substructure should take into account the type of foundation mate- rial, upstream and downstream water pressures, uplift forces, lateral earth pressures, weight and thrust of equipment, water hammer force, ice pressure, and earthquake-induced forces. ASCE/EPRI Guides 1989 3-22 3. Substructure Components The components of the substructure are: • Water passage; intake and spiral or semi-spiral case • Draft tube • Dewatering and drainage sump a. Water Passage. -Substructures are constructed exclusively of concrete or reinforced concrete. In general, the substructure may be classified according to the water passage requirement of the type of turbine used. These can be broadly classified as: • Open flume setting (figs. 3-1, 3-2a, and 3-3) • Metal or concrete casing for vertical units (fig. 3-2b) • Metal or combination metal-concrete passage for horizontal units (fig. 3--4) The dimensions of the water passage are generally fixed by the turbine manufacturers. These dimensions determine the spacing between units and the width of the powerhouse substructure. Figures 3-30 through 3-36 give suggested dimensions for preliminary layouts. ( 1) Low-Head Plants.-The intake should be designed to provide the best hydraulic sys- tem to obtain a uniform accelerated flow with minimum losses. The type of equipment dic- tates the type and shape of water passage. In an open flume setting, the turbine sits in an open pit (fig. 3-32). In a spiral case setting (for vertical unit), the water is directed towards the turbine and is uniformly distributed into the turbine (figs. 3-31 and 3-33). Reaction turbines are generally provided with adjustable vanes called wicket gates. These gates surround the turbine and regulate the flow of water into the turbine The wicket gate settings (openings) are controlled by the governor operated by hydraulic servomotors. (2) High-Head Plants.-The water is conveyed through a flume and/or a penstock to the turbine. The penstock could be made of concrete, steel, or wood. The allowable velocity in the penstock varies depending on the material, optimum diameter, maximum flow, and hydraulic transients. ( 3) Spiral Case.-See the Conventional Hydro Guidelines for typical spiral case geometry. (a) Permissible velocities. -The velocity inside the spiral case or passageway is con- trolled by the type and characteristics of turbine used and is the responsibility of the turbine manufacturer. However, the approach velocity to the intake and the exit velocity is the con- cern of the design engineer. To reduce intake losses, the velocity must be kept low. Fish and wildlife agencies require very low velocity in front of the trashrack to minimize impingement and passing of fish. (b) Intake velocity.-It is recommended that the gross velocity through trashracks be kept below 3 ft/s (0.9 rn/s) to satisfy agencies and to minimize the head loss. Substructure components Water passage Dimensions Low-head plants High-head plants Spiral case Permissible velocities Intake velocity 3-23 ASCE/EPRI Guides 1989 Exit velocity Draft tube General Draft tube for impulse turbine Size Thrbine setting (c) Exit velocity.-The exit velocity should be as low as practical, preferably less than 6 ft/s (1.8 m/s). Depending upon the downstream bed material, appropriate scour protection may, if needed, be provided. b. Draft Tube. -'The draft tube conveys the water from the discharge side of the turbine to the tailrace. For reaction turbines, it is an important part of the powerhouse structure and is designed to minimize exit losses. This is critical because any loss in a small-head develop- ment represents a large percentage of the available resource. The draft tube is designed to recover the kinetic energy by gradually reducing the velocity. In cases where a runner is located above the tailwater and is within the atmospheric head, the draft tube also helps in regaining static suction head. This is possible when the outlet of the draft tube is sufficiently submerged to ensure a water seal. (The negative static head on the runner is added to the positive head from the headwater to make up the total static head on the numer.) However, it should be noted that excessive negative head may cause damaging cavitation to the runner. Draft tubes for impulse or Pelton turbines that rotate in the open air are essentially enclo- sures to contain the spray and need not be hydraulically efficient Specifications for the size and shape of the draft tube are provided by the equipment manu- facturer who nonnally guarantees the turbine output. Some of the commonly used shapes and their dimensions are shown on figures 3-18 and 3-19. The vertical conical draft tubes are easy to construct but require excessive excavation. The elbow draft tubes require less excavation but are complicated to construct. The maximum angle of flare from centerline is limited to 6°. Draft tubes can be made of steel, cast-in-place concrete, or a combination of steel and concrete. The individual site and turbine used will dictate the type and size of draft tube. See the Conventional Hydro Guidelines for details on draft tubes. G. TURBINE SETTING The minimum tail water elevation governs the setting of the turbines. This setting is critical in avoiding serious cavitation of the turbine blades and spiral case. If necessary. slight modifications in specific speed are advisable to avoid cavitation. Extreme cavitation causes loss of efficiency and loss in material of the turbine and draft tube (lining) by pitting; this reduces the life of the equipment. See the Conventional Hydro Guidelines for more details on cavitation. In general, the higher the specific speed or the higher the water velocity through the runner, the lower the setting of the runner should be to avoid cavitation. Figure 3-20 gives the Preliminary settings for the Francis and propeller runners for different specific speeds and heads to minimize cavitation. Bureau of Reclamation Engineering Monograph No. 20 Selecting Hydraulic Action Turbines [USBR, 1976] contains useful data for turbine setting. A tail water depression system can be used to depress tail water on impulse turbines, if the tailwater caused by high flows rises above the minimum. Based on the headwater and tail- water rating curves, the turbine manufacturer suggests the final turbine centerline setting to avoid cavitation. The turbine setting is the responsibility of the hydraulic turbine designer and supplier. ASCE/EPRI Guides 1989 3-24 : !.,',. •t '. r, . : .:;.· ·• ·~·20 30 .. • ~· * ' 'l ' ' ~' , .... ' '' '•' ' -:.: . ' ·' . ' ;,,': ·.·:< Vertical conical draft tube Spreading draft tube 60\ _ .. r-~ ~-------~--~---~ D -· :_ · · 20 sq. Ll ----------------j 1-. ----4 to 50---~ Conical draft tube ~---4Dr-----~ Elbow draft tube "S" Draft tube Figure 3-18. -1)pical draft tube shapes. 3-25 ASCE/EPRI Guides 1989 ;p. Vl m '"1:1 ~ a c:: i5: (11 "' -\0 00 \0 :G 0.. GATE SLOT SECTION A PLAN 3 + t_ RI.X'JNER I I f I GATE SLOT CD 1.o5o ---t_ ® 1.350 SECTION 1&2 n 1.50 I I I \_ lk.,_J SECTION r7 r '[~,:~~ L; ~·::-~ SECTION B SECTION C j Figure 3-19.-Typical draft tube layout (pit turbine). SECTION 3 r 1.90 l I 1.90 SECTION 4 1000 900 800 700 600 500 400 300 250 200 150 .. .:! ..,; .. 100 .. ... .... 90 .. iii 80 IIi: 70 60 50 40 30 25 20 15 10 Correction to H • lor temperature and elevation ELEV. so . 0 +0.-4 000 -0.3 1000 -0.9 ~-!.6 -2.2 80 90 100 110 120 100 !! .. c c 2 ~ .!! 150 o; Q. 0 0. 'i. 200 Example Rated head -70.0' N. -69.0' 3000 •coo 5000 H. (el. 0.0 temp. 70°) •7.5' -3.3 -4.5 -5.6 70° o.o -0.7 -1.3 -2.0 -2.6 -3.7 -4.9 -e.o H. (11.1000 temp. 50°) •7.5'-.9'•6.6' 90° -o.a -l.S -2.1 -2.8 -3.4 -4.5 -5.9 -e.e 16 15 14 13 12 11 10 9 8 .: 5 ~ 4 3 2 1 0.0 -1 -2 -3 -4 -5 -6 -7 -8 -9 -10 -11 -12 Figure 3-20.-Hydraulic turbine settings. For preliminary studies only. [Creager and Justin, 1950]. 3-27 ASCEIEPRI Guides 1989 Excavation General Vertical units Horizontal units Factors affecting excavation Thrbine setting Structural frames Concrete box H. EXCAVATION 1. General The cost of construction is generally affected by the excavation required for the substruc- ture; this may dictate the type of unit selected for a particular site. 2. Excavation Requirements a. Vertical Units. -Draft tubes for vertical units usually require deeper excavation than horizontal configurations. b. Horizontal Units. -Because of its configuration, a tube turbine may require less exca- vation than pit and bulb turbines. Bulb and pit turbines require less overall excavation than venical units. 3. Other Factors Affecting Excavation a. Foundation Ma~rial •Rock • Sand/gravel • Clay • Requirements of piles b. Turbine Setting • Cavitation • Minimum tailwater requirement • Draft tube design • May need deeper intake to avoid vonex at intake I. STRUCTURAL REQffiREMENTS AND ANALYSIS 1. Structural Frame The structural frames for small-scale hydropower plants fall into one of two main cate- gories: a reinforced concrete box substructure; and a superstructure, such as a frame with siding, or a prefabricated building. Selection should be governed by the site conditions, unit costs, and operational considerations. Use of the concrete box for both sub-and superstructure is a good solution at sites with low machine settings, where the structure is subjected to high tailwater and backfill load- ings. When the site conditions allow a very shallow substructure, care must exercised to provide adequate mass for turbine-generator equipment to avoid damaging vibration dur- ing operation. ASCE/EPRI Guides 1989 3-28 Superstructure design, where it is not dictated by site conditions, is strongly influenced by the choice of powerhouse crane equipment. If a pennanent onsite crane is provided, the superstructure frame must accommodate the crane rail loads. Adequate hook coverage must be provided over the equipment and into the erection/laydown areas as well as to transportation access areas. If mobile crane equipment will be used, only adequate access openings in the roof must be provided, to remove all major equipment for maintenance or repair. Detailed analysis and design must be suited to the types of frame and the applicable load- ings. In general, the designer should aim to provide a design that is cost effective. The use of special grades of steel or even fonned steel shapes that are not readily available should be avoided. For example, specifying many different reinforcing bar sizes on a small hydro project may become costly. Instead, the reinforcing bar spacing should be varied to provide a balanced reinforced concrete design adequate to resist varying loading conditions, while maintaining unifonn concrete thickness. This may result in less than optimum design for some applications, but lower overall construction costs due to material purchasing limita- tions and construction simplicity. In the fmal analysis, the designer must detennine, based on the site and local situation, which design criteria are most applicable to the specific project 2. Specifications The powerhouse design should be based on the applicable codes, standards, specifications, and references. See the list below: • Building Code Requirements for Reinforced Concrete, ACI 318 (latest edition) • Design Fabrication and Erection of Structural Steel for Buildings (AISC) (latest edition) • Structural Welding Code, Steel AWS-0.1.1 (latest edition) [AWS] • Local and State building codes • Uniform Building Code (latest edition) [UBC] • American National Standards Institution (ANSI) A58.1 [ANSI, 1982] • Naval Facilities Engineering Command Design Manual 7.2 [NAVFAC, 1982] • USBR, Design of Small Dams, chapter VIII [USBR, 1987]. • Applicable finn or company standards a. Concrete.-Minimum suggested design strengths are listed below: • Structures: 3,000 lb[ln2 at 28 days (superstructure); at 90 days (substructure) • Mass fill: 2,500 lb(In2 at 28 days • High-velocity water scour areas: 4,000 lb(In2 at 28 days b. Reinforcing StuL-ASTM A 615, grade 60 c. Structural Steel. -ASTM A 36 d. Bolts Used in Structural Joints. -ASTM A 325 Super- structure design Small hydro design goals Reference specifications for design Material specifications 3-29 ASCE/EPRI Guides 1989 Design loads for steel Design loads for concrete Powerhouse Jive loads Cranes e. Anchor Bolls. -ASTM A 307 grade B (minimum) f. Welds. -Made with E70 electrodes g. Rock Bolts.-Refer to Post Tension Institute Manual 3. Design Loads a. Loail Combinations for Steel Members. -Load combinations for steel members should be designed as follows: S = defined in [ AISC], D = dead load, L = live load, and Wand Hare defined by ACI 318-77, section 9.2. S=D+L+H 1.33S = D + L + W (3-1) (3-2) b. Loail CombiMtions for Concrete Members.-Load combinations for concrete mem- bers should be designed as follows: U is defmed in ACI 318.77, section 9.2 with strength reduction factor as per section 9.3. U = 1.4D + 1.1L (3-3) U = 0.75 (1.4D + 1.7L) +1.7W (3-4) U=0.9D+ 1.3W (3-5) U = 1.4D + 1.1L + 1.7H (3-6) If there are no code requirements, the following are suggested minimum live loadings may be used: • Operating floor: 250 Iblft2. • Stairs, platforms, landings: 100 lb/ft2. • Floor gratings: 250 lb/ft2. • Roof (where access is provided): 40 lb/ft2 on top of the roof plus concentrated loads at center of the beams as follows: o Main members: 5,000 lb o Secondary members: 2,000 lb • Powerhouse crane: maximum rated load plus 10 percent for impact. vertically and horizontally, and traverse load. • Mobile crane: where access allows use of a mobile crane, a foundation wall surcharge of 400 lb[In2 for construction or maintenance condition should be considered. ASCE/EPRI Guides 1989 3-30 • Dynamic loads: the dynamic loads imposed on the substructure by the turbine/genera- tor equipment and any thrust from the penstock must be considered. If these loads are not accounted for in the powerhouse substructure design, they must be resisted by other specific design elements. c. Seismic Loads. -Lateral structural loads should be in accordance with the Uniform Building Code (latest edition) or applicable local or federal codes. d. La~ral Eanh Pressure. -Static earth pressure should be determined in accordance with the Naval Facilities Engineering Command Design Manuo.l7.2 [NAVFAC, 1982]. J. STRUCTURAL STABILITY REQUIREMENTS 1. Loading Conditions Acceptance criteria from FERC Engineering Guidelines [FERC, 1988] should be used to eva,luate stability requirements for the powerhouse. Each loading case should include uplift, sliding, and overturning forces. Five loading cases should be considered : Case 1, Construction: Case II, Operating: Case III, flood: Case IV, Seismic: Case V, Dewatering: Construction equipment surcharge Lateral soil pressure Without and with equipment installed No roof in place Normal headwater Normal tail water (or lowest, if more severe) Uplift forces Lateral soil pressure Turbine/generator thrust Hydraulic thrust in penstock (if applicable) Case II except: High headwater or QlOo High tail water or Qwo Case II plus: Horizontal loads Venicalloads, if applicable High headwater High tail water (or low if more severe) Uplift forces, as applicable Lateral soil pressure Maintenance equipment surcharge Applicable ice pressure and hydrodynamic loading due to seismic forces should be deter- mined according to [USBR, 1987]. Dynamic loads Stability loading conditions Load cases 3-31 ASCE/EPRI Guides 1989 Stability factors of safety Allowable stresses Soft foundations The minimum acceptable factors of safety for the various loading conditions should be taken from the applicable code. The FERC recommendations for the low-hazard-potential structures are: Loadins case UJ!Iift (buol&n£I) Slid ins I N.A. 1.25 II 1.2 2.00 III 1.1 1.25 IV 1.1 1.00 v 1.1 1.25 In assessing the adequacy of the structure against overturning on a rock foundation, the resultant of all combinations of horizontal and vertical loads acting above any horizontal plane through the structure or at its base shall fall within the center 113 of the plane for cases I and II, and within the center lf2 of the plane for cases III, IV and V. To be adequate against overturning requires that the allowable unit stress (tension or com- pression) of the concrete or rock, whichever is less, not be exceeded. The allowable stress (tension or compression) should be determined by dividing the ultimate strength of the con- crete, concrete-rock interface, and the foundation rock by the appropriate factor of safety. 2. Soft foundations Although soft foundation conditions would eliminate a chosen site for a conventional hydro plant, because of the smaller size and resulting reduction in total foundation loads, small hydro plants can be adapted to these less desirable conditions by the use of piles. The stability of a powerhouse fowxied on piles depends on the load-carrying capacity of the piles. The piles should be designed to resist the net vertical, horizontal, and cross- canyon loads applied to the structure. Two sets of allowable stresses must be checked to ensure the stability of the powerhouse. First, the allowable stresses per pile based on the load-carrying capacity of the soil must be checked. Under this set of allowable stresses, the pile capacity will be based on the allow- able bearing stress of the soil, the allowable friction capacity of the soil in compression and tension and others. Second, the allowable stresses per pile based on the yield strength of the pile material and others must be checked. Combined stress criteria due to combined bending and axial loads must be satisfied. If the pile stresses fall within the limits based upon the soil capacity and the limits based on the material capacity, the powerhouse is considered stable. In some cases, the deflection criteria must also be met. The actual horizontal and vertical loads per pile are a function of the interaction between the soil and the pile. The references below can help solve the soil-pile interaction problem. ASCE!EPRI Guides 1989 3-32 • Naval Facilities Engineering Command Design Manual7.2 [NAVFAC, 1982] • COE computer program LMVD Pile (3-dimensional analysis based on [Hrennikoff, 1950] • SAPIV computer program with 3-dimensional pile load element 3. Uplift When they are remote from other structures, small powerhouses are designed as indepen- dent units. Under these conditions, full uplift due to the buoyant effect of maximum expected tail water conditions should be used for stability calculations. When they are close to dams or reservoir retaining structures, the uplift criteria for the powerhouse should be consistent with the criteria for the other structures. Refer to the Conventional Hydro Guidelines for this criteria. An ongoing study by EPRI addresses uplift criteria for concrete structures and should be consulted as this information becomes available. FERC has issued guidelines for considering uplift. K. HYDRAULIC REQUIREMENTS 1. High Water Levels Small hydro powerhouses should be designed to provide protection from submergence dur- ing flood events, or the risk associated with the flooding should be evaluated. The owner may choose to accept the risks of both the financial and operational impacts of flooding rather than invest the capital to eliminate the risk. Risks that should be evaluated are: •The effect of power loss to a utility system (including power contract requirements) • The extent of the potential damage to the equipment facility • The time and cost to restore the plant to its operational status • The insurability of the potential loss If full protection is chosen, steel mezzanines may be built to carry switchgear and control equipment, or the substructure should be carried to an elevation above the expected maxi- mum high water level (MHWL). Penetrations into the powerhouse below the MHWL should be avoided wherever possible or made permanently watertight. As discussed under Section B, ••Powerhouse Types," siting options for small hydroplants may minimize flood impacts by using submersible units and placing electrical and control equipment above the MHWL. 2. Seepage and Drainage Seepage into the powerhouse should be minimized by properly positioning sealed con· struction joints and by careful design and construction techniques. Seepage inside the plant should be controlled by floor slope and gutters as in conventional hydroplants. A small drainage sump, using a standard float-controlled pump is normally provided for pumping seepage and leakage to a point above MHWL for discharge outside of the powerhouse. Uplift Flooding conditions Protection against flooding Seepage prevention 3-33 ASCE/EPRI Guides 1989 Powerhouse equipment Station diagram L. POWERHOUSE EQUIPMENT 1. General Typical powerhouse equipment layouts are shown on figures 3-30 to 3-37. These compo- nents include the turbine and its generator, which may be coupled directly to the turbine or coupled through a gearbox to increase the turbine speed for a smaller high-speed generator. The power flow is controlled by a governor cubicle that adjusts the regulating gates, noz- zles, and/or the turbine blades to the electrical load while maintaining the speed of the syn- chronous generator for constant cycle. If connected to a grid, only a gate positioner is need- ed to synchronize with the grid. Each synchronous generator has its own exciter and volt- age regulator with its power terminals connected to a switchgear cubicle. A power trans- former is then used to step up the generated voltage to that of the transmission line. A line transformer is used for fault protection purposes when generating at the transmission line voltage. A breaker(s) is provided on the high voltage side of the transformer to electrically disconnect the power generating unit(s) from the transmission line. A governor is not required for induction (asynchronous) generators that produce available energy, irrespective of load, and feed it into a large electrical grid. The generator electrical current and frequency, in this case, is maintained by the grid reactive power. The powerhouse may be equipped with pressure oil system for hydraulic operation of the intake gate(s) shutoff valves and servomotors of the turbine wicket gates and runner blades. This usually requires air compressors and oil pressure accumulator tanks. Central cooling of bearing oils may be provided. A draft tube gate or stoplogs should be provided to dewa- ter the unit for maintenance and repair. Whenever required, drainage and dewatering pumps are normally used to drain seepage water and to empty the water passages respec- tively. Fire protection, if considered necessary, is provided by water sprinklers, fire hydrants, portable fire extinguishers, and foam or gas systems. A heating and ventilating system should be designed to prevent freezing during winter shutdowns and overheating of equipment during the summer. A control cubicle is provided for supervisory and local con- trol of the generating unit and the above-mentioned service and auxiliary equipment. a. Station Dillgram. -It is recommended that an electrical engineer be involved at the earliest stage of conceptual design to draw up a station single-line diagram. This diagram must take into account the projected installation of units and the requirements of the power system or industrial loads to be served, such as continuity of service and reliability. A typical example of a small single-unit station connected to a power system distribution line is shown on figure 3-21. The high-voltage circuit breaker could be replaced by fuses, with some loss of protection in the transformer. It could, however, be eliminated if the sta- tion is the only source of power supplying the distribution line. Many switchyard configurations are possible and greater complexity may be justified, par- ticularly for multi-unit stations where flexibility and continuity of service are important. ASCE/EPRI Guides 1989 3-34 TRANSMISSION LIN£ t--' II GROUNDING SWITCH LINE DISCONNECT SWITCH LINE CIRCUIT BREAKER MAIN TRANSFORMER ~GENERATOR ~ CIRCUIT BREAKER STATION SERVICE TRANSFORMER REGULATOR 3 BRIISHLESS EXCITER LOAOS GENERATOR "AT/ON SERVICE 'RCUIT BREAKER Figure 3-21.-Typical single-unit station single-line diagram. 2. Thrbines a. General. -For details on turbines. refer to appropriate chapters in the Conventional Hydro Guidelines. 'The following sections briefly describe turbines for a basic understanding. The turbines suitable for small hydro JX>Wer plants may be grouped in three general cate- gories as shown on figures 3-22 and 3-23 and as described below. Thrbines General b. Types. -( 1) Impulse. -The impulse turbine converts the JX)tential energy of water Types into kinetic energy in a jet issuing from a nozzle. Each nozzle projects a jet of water to the runner buckets as shown on figure 3-22. Hydroelectric JX>wer installations operating under Impulse high heads (generally above 800ft) use impulse turbines such as Pelton wheels and Turgo turbines with single or multiple jets. Each jet is issued through a nozzle with a spear or needle valve used to control the flow. A Pelton wheel installation and a Turgo impulse tur- bine are shown on figure 3-22. 3-35 ASCE/EPRI Guides 1989 RUNNER BUCKET RUNNER BUCKETS a. Impulse turbines. b. Pelton impulse wheel. c. Thrgo impulse wheel. Figure 3-22.-Principles of operation of impulse turbines. [CEA, 1983]. ASCE!EPRI Guides 1989 3-36 The physical size of an impulse turbine is defined by the diameter of its runner and the jet [De Siervo and Lugares, 1978; Brekke, 1987]. (2) Reaction. -The reaction turbine uses the pressure and velocity of water to develop Reaction power (fig. 3-23). Reaction turbines can further be subdivided into Francis or propeller turbines. Propeller turbines are classified as fixed-blade (or propeller) or adjustable-blade (or Kaplan). Figures 3-24 and 3-25 give the general application ranges for standard and custom hydraulic turbines. (a) Francis. -Hydroelectric power installation operating between heads of 50 and 800 Francis feet use low-specific-speed Francis turbines. This type of turbine encompasses radial flow, which must be uniformly distributed by means of a spiral casing connected to the power conduit. Such spiral casing should be made of steel. It may be placed vertically or horizon- tally, depending on its physical size, which is proportional to the runner diameter. For example, horizontal axis spiral casings are used with runner diameters up to 6 feet. A typi- cal arrangement of this type of installation is shown on figure 3-30. Large-diameter Francis runners should be placed vertically, as illustrated on figure 3-31. Francis turbines operating under medium heads with normal specific speeds can have their spiral casing formed in the concrete foundation only when water is supplied through a short intake conduit similar to figure 3-33. High-specific-speed Francis runners can be used in open-wheel pit installations where the runner and its guide vanes are arranged in the intake flume or inside a pressurized vessel connected to the intake, as shown on figure 3-32. (b) Propeller.-Propeller turbines are generally used for heads between 15 and 100 feet U Fixed-blade or propeller. -Propeller turbines have high efficiency at a point near full load, but efficiency drops off rapidly as the load decreases (see fig. 3-26). Therefore, these are best used where the unit can be operated at or near the most efficient point either by changing the head or the flow. 2) Adjustable-blade or Kaplan. In this type, the angle of the blade is adjusted to derive maximum efficiency as the load changes. Kaplan units are made more efficient by provid- ing adjustable wicket gates. The wicket gates direct and control the flow of water as it enters the turbine easing. This is known as a full-Kaplan unit. The efficiency of a full- Kaplan unit (adjustable blade and adjustable wicket gate) stays high for even very large variations in head. The comparison of efficiency curves is given on figure 3-26. Both types of turbines can be arranged vertically in open flumes and in spiral casings as shown on figures 3-32 and 3-33, respectively. In a hydroelectric power installation with very high specific speed, where the head is low and the flow is high, straight-flow turbines can be used. These are the tubular and bulb tur- bines shown on figures 3-34 and 3-35, respectively. In these installations the water Propeller Fixed blade Adjustable blade 3-37 ASCE/EPRI Guides 1989 a. Reaction turbines. b. Cross now turbine. Figure 3-23.-Reaction and cross·ftow turbines. [CEA, 1983]. ASCE/EPRI Guides 1989 3-38 TURBINE RATED DISCHARGE -FT3/S 10 100 1000 10000 :t! <::! I-. ~ ~ =t ~ <::! I.; ~ ~ =t ~ 1:; 1... ..... "" ~ Q: ~ I.; ~ ..... ~ 1:: 10 100 1000 TURBINE RATED DISCHARGE -M 3 /S Figure 3-24.-Th.rbine application chart. [CEA, 1983]. 3-39 ASCE/EPRI Guides 1989 Cross flow Other types Thrbine selection General 7000 5000 3000 2000 1000 i=" 500 UJ UJ 300 LL. 200 0 ~ J: 100 50 30 20 10 5 1 0 20 40 60 1 00 200 400 1 000 4000 10,000 40,000 100,000 TURBINE OUTPUT (KW) 400,000 1,000,000 Figure 3-25. -Application ranges for turbines and pumps as turbines. Allis-Chalmers Corp. passage becomes large enough to accommodate a bulb-shaped chamber or a center pier pit where the generator can be located. When the generator is mounted on the rim of the runner with special water seals, a short bulb is still required for structural and hydraulic purposes. 3) Cross-flow turl:>ine. Cross-flow turl:>ines are commonly known as Ossberger turl:>ines. This type is generally set in a broad open pit layout, where a wide water jet of rectangular cross section passes through the blades twice. The water flows first through the periphery towards the center then, after crossing the open center space, it flows from the inside out- wards. Water is guided towards the turl:>ine by one or more guide vanes located in a transi- tion piece upstream of the runner. Sometimes, a simple vertical draft tube may be used downstream to create suction head. These types of turl:>ines can be used in both the hori- zontal and vertical axis positions. 4) Other types of turbines. -Other unconventional small hydroelectric installations include outdoor power generating facilities as shown on figure 3-4. Submersible turl:>ines and pumps used as turbines are shown on figures 3-14, 3-15, and 3-16. c. Turbine Selection. -( 1) General. -The physical configuration of powerhouses depends primarily on the type and size of the hydraulic turl:>ine used. The turl:>ine should be able to produce required power at maximum efficiency and at the highest possible speed. The higher speed reduces the size of hydraulic equipment and generator. Therefore, a bal- ance between the size, efficiency, and speed is required. ASCE/EPRI Guides 1989 3-40 ~ > 0 z LLJ 0 -a.. a.. LLJ 100 90 80 70 60 ~0 40 30 20 0 P£LTON7 OSSB£RGERI\.-...... -~ ... --.~ .,. ~ tt.·· . . V"'"\ ~< -~ ~ L.-• ..... ~ J /. L~ ;I"'•' 1/ ~ .··1 .·~ J /! :I . .. , J l! r~~ ." I I ~ _I :; ~ • I r"-KAPLAN . ; ~· I . :· ~ ! l I i ~i ~~ J 4 i ! I ~ 'r-PROPELLER i i : I J ~ I . I i . : I JJ : L . • ii. . : '1, J . I " . ~FRANCIS . . . . . I i 1 i 20 40 60 B. Q MAX.-% ·-'.....:.: ... ' "' ,....__ ··!'r ~ I ·--·- Lru ~GO IMI ~ULS£ eo 100 Figure 3-26.-Effect of load change on efficiency for hydraulic turbines. [CEA, 1983]. 3-41 ASCEIEPRI Guides 1989 Turbine- generator selection Net head determination Flow selection Capacity circulation 10 0 ... c • .. .. • ... . "" .. " • .. -i:i 98 96 ( 92 II{\ ~ I I •l 88 I II I lj ~M>, '• I c.-·-• ... r I I I 1 I I I I ..._ T~bulor type I AdJustobl ... blo e 1Kapkm and ltud·blade propeller type : I JUS 0111e:DI0<!8 QI~IClOIIO!_:!I( W I me rioi type li Fronci' type I I 82~+-~~~7~~·~~~0 :::=:=~=~~=:~~,~~==~=:=:=~:=:=:=:==~=:=:==:=: ~o~~7zo~--~~o_.~,o~~e~o_.~,o~o~~,~2o~----,4~0~~,6~o~-,e~o~~zo-o~~Z~2o~~,~~o~~zso Sll•cilic tpud ot rottd upocltJ Figure 3-27. Typical peak efficiencies of various turbines in relation to specific speed. [Davis and Sorensen, 1969]. (2) Steps in Selecting a Turbine/Generator. -The following steps may be followed to help select a turbine/generator. (For details refer to Division I, "Planning," Chapter 5, "Estimating Plant Capacity and Power Output.") (a) Select net design head (Hd).-Net head (feet)= pool elevation-tailwater elevation -all losses (feet). 1be selection of the design head is important because the turbine manufacturer will design the turbine for that head. Most turbines will operate between 1.30Hd and 0.50Hd, but the efficien- cy will change (refer to figs. 3-26 and 3-27) if operated Wider different head than design head. (b) Select the design flow.-Select from a flow-duration curve. (c) Compute kilowatts and horsepower. -Use the following equations: where: Q = Hd = r = TJ = flow (ft3/s), head, (feet), QHdrn hp= 550 unit weight of water, (lbfft3), and (3-7) (3-7) system efficiency (turbine efficiency x generator efficiency x speed increase efficiency). For preliminary studies, a value from 0.8 to 0.85 is appropriate. ASCEIEPRI Guides 1989 3-42 (d) Determine nwnber of units.-Once the total capacity of the proposed plant is comput- ed, detennine the optimum number of units for the site, based on the flow characteristics of the river. Refer to Vol. I, Division I, chapter 5, "Power Plant Sizing." The correct efficiency is available from the equipment manufacturer. (e) Turbine type selection.-Based on net head, the design flow, and horsepower, the ini- tial selection of turbine type can be made from figures 3-24 and 3-25. Estimate the specific sqee<i and identify feasible type of turbines. The selection of turbine type is based on relative specific speed, which depends on the rated discharge and head. Specific speed provides a means of comparing the speeds of all types of hydraulic turbines on the same basis: head and horsepower (or kilowatts). Hence, the specific speed can be defined as the number of revolutions per minute at which a runner will produce one horse- power at one foot of head. Thus, all homologous turbines of the same type but of different size, have the same specific speed. The equation of specific speed for a given turbine (based on model tests) is: VP' Ns=N-s74 H where: N s = specific speed, N = revolutions per minute, P = horsepower, and H = head (feet). The range of specific speed for each type turbine is given below: Type Impulse Francis Propeller Head, ft 300 and up 50 to 1500 15 to 100 N 3 to 6 (per jet) 22 to 80 70 to 185 (3-9) Empirical equations to calculate the ranges of spec.i fie speeds are given below [USBR, 1977]. Figure 3-28 gives approximate recommended specific speeds for various heads for turbines. See also [Warnick et al., 1984]. Francis type: (3-10) 1100 v'H Propeller: 950 v'H (3-11) Impulse: N = 85.49 and s H0.243 (3-12) Specific speeds of turbines 3-43 ASCE/EPRI Guides 1989 Turbine efficiencies 10 I 20 I HEAD (FEET) 40 60 80 100 200 I i I I i i I i 400 600 1000 i I i J i I 2000 I 200 100 80 60 U) 1- z 40 :::> u) ::i ~ 20 c U.J w 0. (I') u 40 1--+--t_.JHi-!-+H----+--+~f-+-.j.......IH--!-!--N • 90/H0.l!i Penon_-+---',__., 10 L;: u f:::::: • _ / Lindestrom KMW I no date) 8 ~ N, • 85.49/WUC' Peltonli f=:~k 20 J--+---+--l--l-+-+-11+----+de_Si_·•rvo-4•-nd_LAi (19781 I IT _ 1- 6 3 8 ,. 10 20 60 80 100 200 400 600 H, raud head in meten Figure ~28. -Approximate recommended speciftc speed for hydraulic turbines. [Warnick, 1984}. 4 It may be noted from the specific speed equation (3-9) that for a given power capacity and head, the turbine speed is directly proportional to specific speed. Hence, there is a tenden- cy to use a high rpm machine to reduce the diameters and weights of the turbine, even at the expense of efficiency. Figure 3-27 shows the variation in efficiency with specific speed. In a low-head hydro plant, the efficiency is important because the machinery is large and speeds are low, which will result in a very large generator. This drawback is overcome by providing a speed increaser (gear box) between the low-speed turbine (machinery) and the generator. The gear box can increase the rpm two to four times, thus reducing the size, weight, and cost of generator. The design of an impulse turbine is complex. The reader is advised to refer to the Conventional Hydro Guidelines and to [Davis and Sorensen, 1969; Brekke, 1987; and De Siervo, 1978]. The design of pump as turbine for specific sites has not been discussed in detail. For detailed design considerations see [Shafer, 1982; Warnick et al., 1984]. 'The basic design considerations for turbine selection are similar to those outlined. (f) z ASCE/EPRI Guides 1989 3-44 ( 1) Efficiencies of Various Turbines. -Estimate the expected efficiencies of feasible types of turbines and select the best Efficiency of the turbine varies with the flow (quantity) and head. The flow can be controlled by the wicket gate opening (commonly known as gate setting). A comparison of efficiencies for various types of turbines with respect to varying flow is presented on figure 3-26. Note that a turbine is most efficient when it operates at 80 percent of its design load. The performance characteristics of pumps as turbines are pre· sented on figure 3-29. Figure 3-27 gives efficiency curves for various turbines with respect to specific speeds. These curves are included for preliminary design information and understanding. The tur· bine efficiency curves for various heads and flows for the selected turbine are furnished by the turbine manufacturers. (2) Homologous Equations.-The turbine manufacturer determines the characteristics of each turbine based on the test of a homologous model. The following homologous equa· tions can be used to determine the power, speed, and discharge of a homologous runner of a different diameter under a different head for the same efficiency. These equations may also be used to calculate power, speed and discharge for the same runner diameter or for constant head. For constant head For constant diameter Q2 =[ H2]1J2 Ql HI where: P 1 and P2 = horsepower for different conditions, dt and d2 = runner diameters for different conditions (inches), Q 1 and Q2 = discharge for different conditions (ft3/s), Nt and N2 = speed (rpm), and H1 and H2 = head for different conditions (feet). (3-13) (3-14) (3-15) Equations (3-13), (3-14), and (3-15) are helpful when conducting the efficiency tests for unit acceptance. Homologous equations 3-45 ASCE/EPRI Guides 1989 Flow-percent ol pu.mp BEP flow a. Normalized performance characteristics for a pump operating in the normal mode and in the turbine mode. Tuttline capaQiy b. Typical turbine performance curve for constant-speed operation. ·~ Ca~dty I ~~----+-----~-----+----~~~~ " > '-'I ~I ~~I----~~~~~~--~--~,-----~ ~I ""I I iurtline soeeo c. Typical turbine performance curve for constant-head operation. Figure 3-29.-Performance characteristics-pump as turbine. [Shafer, 1982]. ASCE/EPRI Guides 1989 3-46 (3) Turbine Dimensions and Space Requirements.-The overall dimensions of a power- house depend primarily on the type and number of generating units it will house and whether a service bay is required. It is, therefore, important to determine the space require- ments for a single generating unit. Figures 3-27 and 3-30 through 3-36 show layouts and section views for different types of generating units. The dimensions of major components and equipment shown are presented in terms of the runner diameter for preliminary layout. The final layout should be based on the actual equipment dimensions obtained from the equipment supplier. The approximate runner diameter can be calculated using the follow- ing equations [USBR, 1976]: For Francis runners: For axial flow runners: where: D = runner diameter (feet), H = design head (feet), N 9 = runner specific speed, and N = turbine speed. (3-16) (3-17) To calculate the size of a Pelton wheel is more complex. For details refer to the Conventional Hydro Guidelines. An approximate method is given below: and where: d p H D = = = = d _ 15.5P -3/4 H D -54.5d -N 9 diameter of jet for single running (inches), horsepower, head (feet), and pitch diameter of single runner (inches). See also [De Siervo and Lugaresi, 1978]. (3-18) (3-19) Thrbine dimensions and space requirements Runner diameter 3-47 ASCEIEPRI Guides 1989 L . . ":! Equipment: 1. Generator 2. Thrbine 3. Governor 4. Generator breaker 5. Control panel 6. Switchgear 7. Sump pumps and dewatering pumps 8. Air compressor and tank SECTION A bli~-----' STOP I..OG SLOT ~ l · --i: UNIT _j =j TAII..RAC£ ___.- . - li----_S'TOP LOG HOIST 0 r-~~~~--~~~N~a~---~ Figure 3-30. -Powerhouse layout-horizontal Francis turbine. [USBR, 1980]. ASCEIEPRI Guides 1989 3-48 Equipment: 1. Generator 2. Turbine 3. Governor 4. Generator breaker S. Control panel TURBINE SHUTOFF 1/Al.VE 6. Neutral ground cubicle 7. Cooling pumps 8. Sump pumps 9. Air compressor and tank SECTION A -• STOP \..OG Sl.OT.;. 0~ -\_UNIT __j "'' "'I TAIL.RAC£--' e . ... ~ ...,; • 1 .. ~ .. 0 0 .. .:!: Figure 3-31.-Powerhouse layout-vertical Francis turbine. [USBR, 1980]. 3-49 ASCE/EPRI Guides 1989 A _j Equipment: 1. Generator 2. Thrbine 3. Governor 4. Generator breaker 5. Control panel 6. Neutral ground cubicle 7. Sump pumps 8. Air compressor and tank NOTES: "'§I QQ .,., ,.,,., .. 30l·9' C3o,·a.7ml :. ~ ~ !LL----__....., SECTION A 1. Arrangement and equipment are schematic. 2. Layout, equipment, and dimensions shown may vary according to site-specific power plant conditions. Figure 3-32.-Powerhouse layout -open flume turbine. [USBR, 1980]. ASCE!EPRI Guides 1989 3-50 Equipment: 1. Generator 2. Turbine 3. Governor 4. Generator breaker S. Control panel 6. Neutral ground cubicle 7. Cooling pumps 8. Sump pumps 9. Air compressor and tank NOTES: 1. Arrangement and equipment are schematic. 7 h.J----1..---:...J (401 •3.7ml SECTION A STOP l.OG Sl.OT ~ J ·~UNIT _j ~~ TAl !..RACE-- STOP t..QG HOIST . i N ... 'l:' .... ~ ·~ .. Q .. 2. Layout, equipment, and dimensions shown may vary according to site-specific power plant conditions. Figure 3-33.-Powerhouse layout -propeller turbine with headworks. [USBR, 1980]. 3-51 ASCE/EPRI Guides 1989 . e <1:1 CD a: NQ N L_ Equipment: 1. Generator 2. Thrbine 3. Governor e ... 9 "!:!! 4. Generator breaker 5. Control panel 6. Neutral ground cubicle 7. Speed increaser 8. Sump pumps 9. Pressure set NOTES: 1. Arrangement and equipment are schematic. _j~UNIT (701 +1.8• I i ·-~UNIT SECTION A 2. Layout, equipment, and dimensions shown may vary according to site-specific power plant conditions. Figure ~34. -Powerhouse layout -tubular turbine with penstock. [USBR, 1980]. ASCE/EPRI Guides 1989 3-52 ws a - 1. Generator 2. Thrbine 3. Governor 4. Generator breaker S. Control panel 6. Neutral ground cubicle 7. Surge and protection cubicle 8. Sump pumps 9. Air compressor and tank NOTES: 3.50,(5"'W 8. HI~ER) SECTION A 1. Arrangement and equipment are schematic. e ... 0 .,_., .. . ci,.Q ...... ~~ oo I o"1 "'I I ~ \_ q, j e -... o*"" -: .... ~ ·Q "' .... ::! 2. Layout, equipment, and dimensions shown may vary according to site specific power plant conditions. Figure 3-35. -Powerhouse layout -bulb turbine with headworks. [USBR, 1980]. 3-53 ASCE/EPRI Guides 1989 STOP lOG SlOT TAilRACE- 2 ~UNI"!'--· L---~~----~--~W---------~~_,--, ~ Equipment: ..., ·--+--'----'TWc.:.: a 1. Generator 2. Thrbine 3. Governor 4. Generator breaker SECTION A 5. Control panel 6. Neutral ground cubicle 7. Surge and protection cubicle 8. Sump pumps 9. Air compressor and tank NOTES: 1. Arrangement and equipment are schematic. 2. Layout, equipment, and dimensions shown may vary according to site specific power plant conditions. Figure 3-36. -Powerhouse layout -cross-flow turbine. ASCE/EPRI Guides 1989 3--54 3. Generator Gear Box a. GeneraL -In many instances, panicularly with small-capacity hydropower generating units of up to 3,000 kW and low-speed turbines with less than 400 rpm, a speed increaser is used in between the turbine and its generator to raise the speed of the latter. This results in a smaller generator with fewer poles and a lower cost. However, the added cost of the speed increaser may offset the savings of the smaller generator. Therefore, an optimization may have to be carried out in the final layout stage. b. Types and A"angements. -There are two types of speed increasers. The first is the parallel-shaft gearbox used for an in-line arrangement of the generator and turbine. The second is the right angle drive with bevel gears, used where the vertical axis turbine drives a horizontal axis generator. Either type could be used for vertical, horizontal, or even inclined turbines. However, the choice between the two types is usually based on the space and physical arrangement of the installations. Figure 3-30 shows the most common arrangements. c. EjJ'icilncy. -A gearbox between the turbine and its generator introduces some friction losses that could amount to about 2 percent of the output power. Therefore, the real capital cost of using speed increasers should include the loss of about 2 percent of energy produc- tion. Furthermore, gearboxes require additional maintenance and spare pans, particularly, the right angle drive. In addition, the gearbox may be expected to significantly increase noise levels in the powerhouse. 4. Generators a. GeneraL -A generator transforms mechanical energy into electrical energy. For hydro plants, only 3-phase generators are used. Generators may be synchronous or induction type; both are explained below. b. Synchronous Generators. -A synchronous generator maintains synchronism with the frequency, voltage, and phase angle of the power system and because of its design, cannot deviate from these power system quantities. The excitation of the generator is a direct cur- rent (de) system. The excitation of the synchronous generator is controlled to provide volt- age control before synchronizing and to provide either power factor or Var control after the generator is synchronized to the grid. Synchronous generators are used in power systems where the output of the generator provides a sufficient portion of the power system load. Most generators larger than 2 MW are synchronous because they are capable of supplying reactive power, thus correcting the power factor of the system caused by inductive loads (motors). Synchronous generators are usually more expensive because of the need for excitation equipment and synchronizing equipment. On the other hand, these generators provide black start capability, which may be helpful in remote and isolated locations where no startup power is available for auxiliary powerhouse equipment. c. Induction Generators. -The major difference between the induction and synchronous generators is that the induction generator cannot generate while disconnected from the Gearbox General Types Efficiency Generators General Synchronous generators Induction generators 3-55 ASCE/EPRI Guides 1989 Generator voltage Excitation Hydraulic power unit Control equipment Governors power system because it cannot provide its own excitation current Induction generators and their associated electrical equipment are usually less expensive than synchronous gen- erators and are generally limited to capacities of less than 5 MW. As explained above, if the power for auxiliary equipment is available from the grid system, then the use of an induction generator can considerably reduce the cost of installation, pro- vided that the utility system is suitable for an induction generator system. d. Generator Voltage. -The power output and speed are dictated to a large extent by the prime mover, the generator voltage choice is essentially electrical and economic. The choice of voltage will be largely influenced by the distance separating the generator tenni- nals from the stepup transfonner and the costs (including civil works) associated with the choice of busbar or cable system for these connections. For a small hydro development, the equipment supplier nonnally suggests the generating volt- age as a part of the equipment package. The most common generating voltage is 4,160 volts. e. Excitlltion. -The field of the synchronous machine, which is earned by its rotor, must be excited with adjustable direct current to regulate the output voltage of the generator. With the development of power thyristors has come the replacement of the traditional de rotating exciter by the solid-state exciter. Smaller synchronous generators (7 MVA or less) are now generally equipped with "brushless" exciters, and certain manufacturers can pro- vide brushless excitation up to approximately 50 MVA. The excitation system includes the automatic voltage regulator (AVR), which monitors the voltage at the generator tenninals and quickly adjusts the alternator field to maintain desired conditions. 5. Hydraulic Power Unit Hydraulic power units are the most widely used system for actuation of the turbine wicket gates. The major components consist of a sump for fluid storage, an electric motor operated pump for supply of high-pressure fluid to the system, an accumulator for storage of hydraulic fluid under pressure, fluid control valves, and a servomotor or hydraulic pis- ton-cylinder combination. The servomotor is mechanically linked to the turbine wicket gates. Pressurized fluid is directed to the servomotors by actuation of the control valves and forces the gates open or closed. The control valves may be manual, solenoid, or pilot- type servovalves. The solenoid and pilot-type servovalves allow interfacing of the hydraulic power unit to electronic or mechanical governors. The accumulator serves as a safety device that provides a reserve of pressurized fluid for closure of the wicket gates in the event of a pump failure. 6. Control Equipment a. Governors. -Hydroplant operation is the function of the quantity of water and head available. The turbine-generator is designed for a head and a flow. Any variation in these must be compensated by opening or closing water control devices (such as wicket gates, valves, or gates) to maintain constant power output, constant speed, constant head level, or constant flow, depending on the type of control parameter implemented. A governor is a mechanical or electromagnetic device that uses feedback based on the control parameters ASCE!EPRI Guides 1989 ~56 to adjust the turbine gates and maintain the turbine/generator operation within preset con- trol parameter set points. Once connected to the grid, the governor cannot change the speed of the turbine/generator, but may vary the power output and flow. A governor detects the deviation from the set point by a feedback element. This deviation is amplified and trans- formed to an error power signal to excite an actuator. The actuator may be an electro- hydraulic valve, a de motor, or some other type of prime mover. There are two basic types of governors. Tile first is the mechanical governor where the speed response element consists of flyballs. The actuator of the governor controls a hydraulic oil system that operates the wicket gates and/or the turbine blades through servo- motors and mechanical linkage. Therefore, a hydraulic power unit is associated with the governor. The second type of governor is classified as electronic. Electronic governors make use of the reliability, availability, and repeatability offered by modem solid-state electronic equip- ment. The electronic governor controls the water turbine through power amplification stages, which normally incorporate a hydraulic power unit. The main advantages of elec- tronic control equipment are increased reliability and accuracy of control. An increase in versatility is also provided because direct load control, as a function of other parameters such as water level, is feasible as is joint control, which allows the total power output of a multiset station to be controlled as though it were a single unit. A schematic of a governor system is presented on figure 3-37. b. Plant Operation. -Small hydro facilities are normally unattended and have semi- automatic controls. Special attention must be paid to formalizing an operation and control plan. Small programmable controllers are often used for plant control and are effective and economical for providing plant control functions. The programmable controller may also transmit plant data to a remote-control center for monitoring purposes, along with any alarms. The automatic-control system of the plant also consists of instruments that measure instan- taneous values of the plant output and compare these with the desired output values. Any deviation generates an error signal which, in turn, directs the plant controller to take cor- rective actions. c. Headwater and Tailwater Measurement Devices.-In hydroplants, provisions should be made to record both the headwater and tailwater. The simplest form of gauge is the graduated staff, from which water levels are read directly. This requires someone to physi- cally observe and record the elevations. Other forms of recorders use pressure gauges, operated by transmission of the pressure at the various depths of water through a diaphragm. Water levels are recorded on a rotating paper drum. The most commonly used recorders are operated by float and continuously record the stage on graph paper with time on the other axis. To obtain accurate readings, the float is usually located in a well to pro- tect it from waves, ice, and floating debris. Electronic sensors and recorders may also be considered. In a plant where a constant headwater must be maintained, the headwater gauge is connect- ed to the turbine flow control device, which automatically adjusts the flow through the tur- Types Mechanical Plant operation Water level measurement 3-57 ASCEIEPRI Guides 1989 General 2. SPEED SIGNAL GENERATORr-----~E~L~EC~~~~R~I~C_A~L---+-----1 SIGNAL t MECHANICAL CONNECTION t TURBINE INFLOW ~ GOVERNOR CABINET HYDRAULIC ,-----....,POWER\ 7. TURBINE •-~~-1 WICKET 6. TURBINE SERVO MOTOR GATES I 3. SPEED SENSOR ELECTRICAL SIGNAL • 4. PILOT SERVO I HYDRAULIC POWER ' 5. MAIN VALVE MECHANICAL LINKAGE lOlL SUPPL I PRESSURE DRAIN LINE l OIL SUMP I I I I I I I I I I PUMP I L----------_.J Figure 3-37. -Simplified schematic diagram of governor system. bine so that a constant head is maintained. In an unattended plant, the water level measure- ment device plays a vital role, therefore, the selection of a strategic location is important. M. AUXIUARY ELECTRIC EQUIPMENT The purpose of a hydroelectric facility is to generate and safely deliver electrical energy to a power grid or community. Therefore, several associated electrical devices are required inside the powerhouse for the safety and protection of the equipment. 1. Switchgear Switchgear The switchgear is the generator and system control equipment required to (I) control the generator, and (2) interface the generator with the utility grid or isolated load. A typical switchgear system includes circuit breakers, busbar, instrument transformer, protection relays, and generator control devices. Either air, magnetic, or vacuum circuit breakers con- trol devices are used to connect or disconnect the generator terminals from the utility grid system. Protective relays are used to protect the generator from damage caused by various fault and failure conditions. The instrument transformers are used to transform high termi- nal voltages and currents down to more usable levels. The transformer representation of ASCEIEPRI Guides 1989 3-58 generator terminal quantities are used for the controlling equipment and the protective relay system. The generator control equipment is used to control the generator voltage, power factor, and circuit breakers. This equipment may include voltage regulators, auto- matic synchronizers, power factor controllers, and circuit breaker controllers. 2. Station Service Transformer Generating auxiliary loads, lighting and station mechanical auxiliaries require from 1 to 2 percent of the station output; the higher percentage applies to a very small station (l,OOOkW). Some of these loads are vital to the operation and security of the plant and to protection against cold weather conditions. As the size or importance of a station increases, so should the security built into the station service systems. The station service supply should ensure the plant and unit auxiliaries of two alternative supplies and with automatic throwover in an unattended station. In some cases, voltage regulation may be required to maintain an unacceptable voltage range for the auxiliary machinery. A station service transformer should be sized to take into account all loads it may have to carry. 3. Motor Control Center The motor control center incorporates all motor control equipment necessary to control all motors for the tumine/generator system and blank auxiliaries. Equipment could consist of indi- vidual disconnects, motor starters, and motor-overcurrent and thermal-overload protection. 4. Distribution Panel A distribution panelboard is used to distribute station power. Typical distributed loads could be control power, lighting, receptacles, and welding outlets,. The distribution panel- board can also provide feeders for sump pump systems, battery charging equipment, venti- lation control equipment, and station unit breakers. S. DC Control Power Supply To provide reliable control and equipment protection under all conditions, hydro plants larger than 500 kW, particularly, those to be remotely controlled require a station battery. In North America, 125 Vis generally specified for medium and larger stations and 48 V or less for small plants and telecommunications. The ampere-hour capacity is usually chosen so that, on loss of alternating current for battery charging, full control is maintained for at least 8 hours and as long as required for initial corrective action to be taken. Typically, the requirement for a 50 MW, two-unit station would be 300 ampere-hours (Ah) from a 125 V supply, while a 100-Ah, 48V supply could suffice for a 2-MW single-unit station. These batteries are generally lead where good ventilation can be ensured and nickel-cadmium where it cannot. A larger station also justifies duplicated battery chargers to ensure continuity of service in the event of a component failure for which no spare is held. Service station transformer Motor control center Distribution panel DC power 3-59 ASCE/EPRI Guides 1989 • Grounding system Lighting Security 1be control power system comprises one or several panelboards to distribute the direct cur- rent among the protection. control. and telecommunications loads. Because the de system is required for emergency shutdown. it must be monitored to assure that it is adequately charged. 6. Grounding System A generating station involves a concentration of assorted machinery in proximity to power sources that can deliver very high fault currents. For personnel safety and to ensure the sur- vival of equipment when a fault occurs. a generating station must have a low resistance connection to the ground mass. typically of 1 ohm or less. The embedded reinforcing and steel penstocks and piping can provide part of the necessary connection to ground, but this must usually be supplemented by external electrodes of driv- en ground rods. frequently planted in the stream in areas that are to be submerged. In addition, frames and enclosures of machinery and electrical equipment must be connect- ed to the station ground through a secure network of low-resistance conductors. The neutral points of the stepup power transformers of the station are generally connected solidly to the station ground, and any ground-fault on the connected transmission system will cause current to flow through these neutrals to ground. The resulting rise of the station ground potential relative to true ground presents a hazard to any metallic telephone circuits entering the station and requires that protective fences surrounding the station be designed so that they do not present a hazard. 7. Lighting Station lighting typically includes general area lighting within the powerhouse, headwork.s. and switchyard. Automatic control sufficient for conducting inspections and discouraging theft or mischief is common. A medium-sized station might have a control room and office area requiring high levels of illumination. The station lighting should permit emergency exit signs and illuminate workshops and storage areas. The lighting load could be expected to amount to 0.2 percent of station output In addition to the basic system, emergency lighting from portable battery-power units must be provided in highly critical areas for safety and operational efficiency. 8. Security Most of the time, small powerhouses are partially manned. that is, a maintenance person is available 8 hours a day, 5 days a week. On the other hand, for a smaller plant, the mainte- nance person may inspect the plant once a day for a short duration. Therefore, the plant must be secured against vandalism. The type of security required depends greatly on the location and importance of the facility. Some of the security measures that can be incorpo- rated into the design are listed below: ASCE!EPRI Guides 1989 3--60 • Security fence with locked gate • Automatic outdoor lighting • Avoid windows • Secure ventilation ducts • Provide bulletproof doors and walls • Provide audio and remote alarm in the door to detect unauthorized entry • Provide video camera 9. Lightning Protection Protection against lightning depends largely on the geographic location of the powerhouse. It is advisable to provide minimum lightning protection of major station equipment such as transformers, regulators, and breakers, even in light thunderstorm areas. In heavy thunder- storm areas, a network of grounded wires is sometimes installed over the powerhouse area to provide protection. 10. Raceways (Conduit and Cable Trays) Various types, sizes, and lengths of wires are required in a powerhouse to connect genera- tors, governors, switchboards, the motor control center, control and other equipment. These wires should be installed in such a way that they can be easily replaced and do not imerfere with day-to-day maintenance. Rigid steel conduits are generally used for station wiring, whereas the cables connecting generators, switchboards and control equipment may be installed in underground conduits or in overhead cable trays. Both underground conduits and cable trays have their advantages and disadvantages. Cable trays are easy to maintain but may sometimes interfere with overhead traveling cranes. Therefore, careful planning is required. Depending on the layout, it may sometimes be necessary to use a combination of all three. 11. Wires and Cables For the smallest stations, main connections between the generator terminals, LV switchgear, and the main transformer are usually made up with cable installed in trenches or along trays, with single-conductor shielded cable for the higher capacities. Auxiliary power cables are generally 600-V class, multi core cable without shielding. Control and protection cables are multicore cable with a preference for shielding so as to not expose solid-state control elements to hazardous surges. Twisted-pair shielded cables should be used for the supervisory control input connections and telecommunications circuits. Neoprene or PVC jacketing of all of the above cables should be sufficient for normal hydro station applications. Lightning protection Raceways Wires and cables 3-61 ASCE/EPRI Guides 1989 Auxiliary power Auxiliary mechanical equipment Dewatering Station sump Cooling water 12. Auxiliary Power Once the hydroplant is in operation, all station power needs are met from this source. If the generators are synchronous, excitation power may not be needed to start the plant. In the case of an induction generator, power from an outside source is needed for the initial exci- tation to start the generators. In addition, when the hydroplant is down, auxiliary power is needed to operate lubrication pumps, station lighting, heating for the plant, and sump pumps. Normally, the transmission line that carries the power from the hydroplant is used to bring auxiliary power to the plant In addition to the above, a de source is generally provided. Several types of emergency equipment, like lubricating pumps, relays, control and communication equipment are pow- ered by the de source. For this purpose, a number of de batteries are provided in the power- house. These batteries are charged from station power. N. AUXILIARY MECHANICAL EQUIPMENT 1. Dewatering System and Station Sump a. Dewatering Systems. -The intake, the water passage, turbine, and draft tube are nor- mally filled with water. As a part of routine maintenance, the turbines should be inspected once a year. Stoplogs or gates are provided on both the upstream and downstream side of the power plant to isolate the water passage from the main body of water. Adequate pipes and pumps must be provided to dewater the water passage. Dewatering arrangements should be different for different types of equipment and powerhouse layouts. b. Station Sump. -A sump to which all seepage will drain must be provided in the substruc- ture. From this sump, the water is pumped and discharged above the tailrace. Normally, dual submersible pumps are provided in the sump, and the motor is located well above the high water level. Each pump should be capable of discharging all of the seepage water. 2. Cooling Water System If possible, the powerhouse should be provided with a water supply for general use and cooling purposes. Water from the river could be used for this. The system requires a set of pumps and a fine strainer. No treatment is usually needed unless the water is used for drinking, in which case a compact water treatment plant should be installed. As an alterna- tive, bottled drinking water may be furnished. In most plants, it may be possible to tap water from the high-pressure sides, e.g., for hori- zontal axis units or units served by penstocks. The equipment supplier determines the requirement of cooling and lubricating (if necessary) water and specifies the method of obtaining water. In an unmanned, automated plant, if clean water is required for cooling and lubricating, the system should be provided with an alarm and a normal shutdown of the turbine/generator in case of filter clogging. ASCE/EPRI Guides 1989 3-62 3. Fire Protection The main cause of fires in hydroplants is overheating of generator windings or a short cir- cuit in control panels. The temperature of the windings is continuously monitored and any overheating automatically shuts the unit down. It is good practice to provide fire and smoke detection devices in the plant, hard-wired to the control equipment, to automatically shut down the power plant and the source of an electrical fire. This is important in unmanned plants. Sometimes automatic chemical sprinklers are provided, but wall-mount- ed fire extinguishers are preferred. The powerhouse must have adequate exits. 4. Eyewash If the power plant has a chargeable de system, an eyewash must be installed nearby (OSHA requirement). It may consist of a mirror with small stand, a squeeze bottle with distilled water, and paper towels. 5. Heating, Ventilating, and Air Conditioning (HVAC) Effective heating, ventilating, and air conditioning are essential for the satisfactory opera- tion of a power plant If the plant is manned, the inside temperature must be maintained at a reasonable level. In the case of unmanned plants, the temperature could vary from 40 °F in winter to about 100 °F during the summer. An elaborate ventilating and heating system is required to neutralize the excessive heat released by the generating equipment It is advisable to utilize the heat generated by the generators to heat the building during the win- ter and to evacuate all the heat during the summer. If a de battery system is provided along with the automatic battery charger inside the pow- erhouse, a separate ventilating system must be provided to meet OSHA requirements. 6. Gates and Valves Each powerhouse must have two positive modes of shutting off flow. Turbines equipped with wicket gates need one additional type of positive shutoff device, such as a headgate, valve, or draft tube gate, which can be closed against flowing water. The gates are impor- tant to prevent any damage to the turbine/generator system particularly during runaway. In automatic or remote-control plants, it may be necessary to make provisions for the emer- gency gate to close automatically in the event of a grid failure or loss of system power. In addition to gates, slots in the water passage may be required for stoplogs both upstream and downstream of the powerhouse. The site conditions dictate the types of gates, valves, and stoplogs to be used. This is an important and expensive part of the project, but is often neglected at conceptual stages. See sections B.2.e and B.3/ for more details. For design considerations, see to the design guidelines for conventional hydro. a. Turbine Shutoff Valves. -When a penstock is used to deliver power flow to the tur- bine, a shutoff valve is usually installed at the turbine inlet to provide emergency closure. Fire protection Eyewash HVAC Gates and valves Valves 3-63 ASCE/EPRI Guides 1989 Intake gates Draft tube gates Stop logs Powerhouse crane Cranes for intake deck Cranes for draft tube deck The most commonly used type is the butterfly valve. However, under high heads, more than 200 meters, butterfly valves with relatively large diameters are not recommended and spherical valves should be used. Figure 3-38 shows a schematic of the two valves. b. Intake Gates. -Intake gates are usually used for open flume installations with no pen- stocks. These gates should be capable of closing under full flow and opening under static conditions to start the turbine. This feature can be provided by wheeled gates with hydraulic operator or rope hoist. Figure 3-39 shows a schematic of this type of gate. c. Draft Tube Gates. -Draft tube gates are suitable for horizontal turbine settings. Because the draft tube gate is smaller than a headgate, it might be preferred for reasons of economy. d. Stoplogs. -Stoplogs and bulkheads are used for lengthy shutdowns. They cannot be dropped against flow; i.e., the turbine should be shut down using the intake gate or the inlet valve before lowering the stoplogs in place. Stoplogs may be made of timber steel or com- posite sections, as shown on figure 3-40. e. Bypass Valves. -Bypass valves are used either to pass riparian flows (particularly if the power-generating units are shut down and no other flow-regulating features are provided) or to relieve hydraulic transient pressures (water hammer) in power conduits. These valves should act as energy dissipators to avoid scour in the tailrace. Fixed cone valves are most suited for this application. Figure 3-41 shows a schematic of this type of valve. 7. Cranes/Equipment Handling a. Powerhouse. -In general, there are three methods of handling materials inside a small powerhouse. The first method uses an overhead top-running crane with rails. The second method uses a monorail system hung from the roof. The third and often most economical method uses a mobile crane that can handle powerhouse material from outside the building through roof openings. The choice among these three alternatives is influenced by many factors including the weight of components to be handled, span and layout of the power- house, accessibility and location of the powerhouse, cost of equipment, and operational requirements of the powerhouse. Sometimes, mobile or stationary jib cranes can be effec- tively used for handling light material. These are inexpensive and can be constructed local- ly. See figures 3-42 and 3-43 for some typical arrangements. b. Intake Deck. -An intake deck is either provided with a gantry crane to handle large gates and stoplogs or a monorail system to handle relatively small and light gates and tim- ber stoplogs. If the intake deck is readily accessible and has no emergency closure gates, the use of a mobile crane may be more economical. If the powerhouse is equipped with an automatic trashrack cleaner, then the same hoist may be used for lifting the headgates or stoplogs (figure 3-44). c. Draft Tube Deck. -In most small-scale hydro installations with draft tubes, stoplogs are used for occasional dewatering. These stoplogs can be handled manually if they are rel- atively small and made of timber. Otherwise, a monorail system is provided. If the draft ASCE/EPRI Guides 1989 3-64 a. Spherical valve. b. Butterfly valve. Figure 3-38.-Thrbine shutoff valves. GATE: STEM WHEEl. TRACK a. Side elevation. !GATE BOTTOM SEAL. b. Section. Figure 3-39. -Intake wheeled gates. 3-65 ASCE/EPRI Guides 1989 TIMBER a. Timber. ASCE/EPRI Guides 1989 STEEL b. Steel. Figure 3-40. -Stoplogs. Figure 3-41.-Fixed cone valve. 3--66 II II COMPOSITE c. Composite. a) OVERHEAD TOP RUNNING CRANE WITH RAILS b) MONORAIL SYSTEMS c) MOBILE CRANE Figure 3-42. -Material handling equipment. 3-67 ASCEIEPRI Guides 1989 LOCKING P/.V-~ LJA'"/LL. T#.ROUG# ...-/_.,..~ SL~ v~ I rveE .9 ,... 3·-o ._,:;. JZO AL CNANN£L('TYI"') •, I"ULL~Y 4 ... }/~·. J1s- 6'1S7 II'<'ON C-4...-ACITY ?t::>O/~. ;5-SCH£0UL£ .t,O .ST<!'LL P/1""<!' SL£CV£ S -00. A<:.. /l/8£ ;.z-J./ALL Figure 3-43. -Portable jib crane. Mead and Hunt Inc. ASCE/EPRI Guides 1989 TRASH RAct Figure 3-44. -Intake gantry crane. 3-68 tube has gates for emergency closing of the system, then it must have a permanent hoist arrangement (figure 3-45). 8. Piezometer System The turbine manufacturer guarantees output based on net head available. [(Headwater ele-Piezometers vation) -(Tailwater elevation) -(Losses at intake)]. To verify the supplier's output, it is important to measure the available head accurately. Piewmeter taps should be provided (in consultation with the equipment manufacturer) to measure head at various locations in water passages. These measurements will then be used to compute the turbine output and efficiency test. Refer to the IEC (International Electromechanical Commission) Code for the field acceptance test. Piewmeters should be capped and preserved for future use to compare the loss in efficien- cy of the turbine. 9. Plant Elevator An elevator is usually a luxury; however, if the power plant is large (deep), it may be a necessity. In small developments, it may not be economical to install an elevator. If provid- ed, it should be capable of carrying a reasonable amount of equipment weight 0. ESmETICS 1. Powerhouse Appearance In a small hydro development, economy is the watchword and esthetics is secondary. The powerhouse building could be made of timber, steel, precast concrete panels, or cast-in- place concrete. If the powerhouse is located in a remote area and unattended, it must be made vandalproof. Windows should be avoided. The door should have a security alarm system. A timber or steel structure must be painted to prolong its useful life. There is no need to paint a concrete structure, but simple features like rustification or grooves may be provided to break the monotony of concrete. If the powerhouse is located in a high visibility area or paric, then the prevalent architec- tural treatment may be required to blend in with the local surroundings. 2. Painting The powerhouse structure may or may not be painted, depending on the type of structure and the owner's requirements. Concrete structures can be left unpainted. Equipment must be painted to meet industry standards. The color of the fmal coat could be of the owner's choice. All piping should be color-coordinated for ease of identification. Elevator Esthetics General appearance Painting 3--69 ASCE/EPRI Guides 1989 Figure 3-45. -Draft tube monorail. ASCE/EPRI Guides 1989 3-70 3. Noise Hydroplants are comparatively quiet and noise is not a problem unless there is a gearbox. Noise Equipment specifications should require a limit on noise, nonnally 80 decibels. No special treatment of the walls is necessary to deaden the noise level. Sometimes, a small wooden cubicle may be provided for an operator and to house controls and telecommunication apparatus. P. REFERENCES ACI (American Concrete Institute), Building Code Requirements for Reinforced Concrete (latest ed.). AISC (American Institute of Steel Construction), Manual of Steel Construction (latest ed.). ANSI (American National Standards Institute), American National Standard Building Code Requirement for Minimum Design Loads in Buildings and Other Structures, ANSI, A58.1, 1982. ASTM (American Society for Testing and Materials), Annual Book of Standards. AWS (American Welding Society), ANSI/ AWS D 1.1, Structural Welding Code-Steels, American Welding Society Miami, (latest ed.). Bourgeacq, J.P., "Inverted Flow Concrete-Built Siphon System," Proceedings, Waterpower '83, vol. I, ASCE, 1983. Brekke, H., "Recent Trends in the Design and Layout of Pelton Turbines," Water Power and Dam Construction, November 1987. CEA (Canadian Electrical Association), "Methodology for the Design and Casting of Small Hydro Plants" Canadian Electrical Association, Research & Development, Suite 580, One Westmount Square, Montreal, Quebec, H3Z 2PG, Canada, 1983. COE (U.S. Anny Corps of Engineers), Design Data for Powerhouse Cranes, Engineering Manual, EM 1110-2-4203, 1968. COE, Design of Pile Structures and Foundations, Engineering Manual, EM 1110-2-2906, 1968. COE, "Wmd and Snow Loads," Engineering Technical Letter, ETL 1110-3-338, 1983. COE, Engineering and Design-Hydropower, Engineering Manual, EM 1110-2-1701, December 1985. COE, Planning and Design of Hydroelectric Power Plant Structures, (draft), Engineering Manual, EM 1110-2-3001, 1986. Creager, W.P., and Justin, J.D., Hydroelectric Handbook, 2nd ed., John Wtley & Sons, Inc., New York, 1950. Davis, C. V. and Sorensen, K.E., (editors), Handbook of Applied Hydraulics, 3rd ed., McGraw-Hill Book Co., New York, 1969. De Siervo, F. and De Leva, F., "Modem Trends in Selecting and Designing Kaplan Turbines," Water Power and Dam Construction, December 1977 and January 1978. 3-71 ASCE/EPRI Guides 1989 De Siervo, F., and Lugaresi, A., "Modem Trends in Selecting and Designing Pelton Turbines," Water Power and Dam Construction, December, 1978. Erbiste, P.C., "Estimating Gate Weights," Water Power and Dam Construction, May 1984. FERC (Federal Energy Regulatory Commission), Office of Hydropower Licensing, Engineering Guidelines For the Evaluation of Hydro Power Projects, October, 1988. Gordon, J.L., "Powerhouse Concrete Quantity Estimates," Canadian Journal of Civil Engineering, vol. 10, 1983. Gordon, J.L. "An Empirical Formula for Determining Powerhouse Size," Hydro Review, vol. VI, No. 1, February, 1987. He, Y., and Huang, T., "Empirical Formulae For Gate Weights," Water Power and Dam Construction, November 1986. Hrennikoff, A., "Analysis of Pile Foundations With Batter Piles," Transactions, ASCE, vol. 76, No. 1, Paper No.2401,pp. 123-126,1950. Leyland, B.W. "Machine Selection and Powerhouse Design For Small Hydropower Schemes," pp. 84-93, Proceedings, Waterpower' 83, held at Las Vegas, ASCE, 1983. Lugaresi, A., and Massa, A., "Designing Francis Turbines: Trends in the Last Decade," Water Power and Dam Construction, November 1987. Lugaresi, A., and Massa, A., "Kaplan Turbines: Design Trends in the Last Decade," Water Power and Dam Construction, May 1988. McAlister, I.J., "Optimization and Selection of Penstock and Power Equipment Minihydro Installations," Proceedings, Waterpower 1983, vol. I, ASCE, 1983. Moore, R.C., "Induction Versus Synchronous Generators," Allis-Chalmers Engineering Review 05R2338-7. Mosonyi, E. (editor), Water Power Development, vol. 1., "Low-Head Power Plants.'' 2nd ed., Hungarian Academy of Sciences, 1963. NAVFAC (Natural Facilities Engineering Command), Design Manual 7.2, Dept. of the Navy, Washington, D.C., 1982. Raabe, J., Hydropower: The Design, Use and Function of Hydromechanical, Hydraulic and Electrical Equipment, VCI Verlag, DUsseldotf, 1985. Rajpal, A.K., Hampton, T.L. and Riley, T.M., "Site, Owner Needs Impact Siphon Hydro Concepts," Proceedings, "Energy Solutions Today for the Nineties," ASCE, 1987. Schweiger, F., and Gregori, J., "Developments in the Design of Kaplan Turbines," Water Power and Dam Construction, November 1987. Shafer, L.L., "Pumps as Power Turbines," Mechanical Engineering, November 1982. UBC (Uniform Building Code) (latest ed.), International Conference of Building Officials. USBR (Bureau of Reclamation), Selecting Hydraulic Reaction Turbines, Engineering Monograph No. 20, Office of Design and Construction, E&R Center, Denver, rev. 1976. USBR, Friction Factors for Large Conduits Flowing Full, Engineering Monograph No.7, Water Resources Technical Publication, Denver, 1961. ASCE/EPRI Guides 1989 3-72 USBR, Reconnaissance Evaluation of Small Low-Head Hydraulic Installations, Tudor Engineering Co., July l, 1980. USBR, Design of Small Dams, 3rd ed., Denver, Colorado, 1987. Warnick. C.C., et al., Hydropower Engineering, Prentice-Hall, Inc., Englewood Cliffs, New Jersey, 1984. Zhong, Z. W., "Vertical Lift Wheel Gates for Sluiceways," Water Power and Dam Construction, February 1987. 3-73 ASCE/EPRI Guides 1989 CHAPTER 4. SUBSTATIONS AND TRANSMISSION LINES CONTENTS Section Page A. Substations .................................................................................................................................................. 4-1 1. [)ead end structure .................................................................................................................................. 4-1 2. Utility metering and protection ............................................................................................................... 4-1 3. Line circuit break.er ................................................................................................................................. 4-1 4. Main transformer .................................................................................................................................... 4-1 5. Bus work ................................................................................................................................................. 4-2 B. Transmission Lines ..................................................................................................................................... 4-2 CREDITS The "Substations and Transmission Lines" chapter was written by: Ray Toney, P.E. Ray Toney and Associates P.O. Box 1342 Redding, California 96099 ASCE/EPRI Guides 1989 CHAPTER 4. SUBSTATIONS AND TRANSMISSION LINES A. SUBSTATIONS 1. Dead End Structure The dead end structure provides the interface between the utility transmission and the hydro plant substation. The transmission line overhead conductors are deadheaded and ter- minated at this structure in the substation. This structure can be used to support a visible disconnect switch, instrument transformer, and metering equipment, if required. The struc- ture is usually fitted with lightning protection equipment to shield the substation area against the possibility of lightning strikes. The substation structure can also be used to mount security lighting for the substation and to support small station transformers that provide control power for the substation area. 2. Utility Metering and Protection Various metering and protection equipment are incorporated into the design of substations for hydro facilities. Protection equipment is used to protect the utility from abnormal con- ditions that could be introduced by the hydroelectric facility. Protection is usually provided for over and under voltage, over and under frequency, and excessive current. Protective relays are used to sense the abnormalities and then trip the substation line circuit breaker. Metering equipment is also provided to record the energy and, sometimes, the reactive power produced or used by the hydro facility. In recent years, meters have been fitted with a pulsing device that feeds the energy or reactive power information to a magnetic recorder. A magnetic tape can then be removed from the recorder and read by a data pro- cessing computer. This data is then analyzed and used for revenue collecting and energy payment purposes. 3. Line Circuit Breaker A power circuit breaker is used in the substation to both protect and isolate the plant and substation transformer from the utility. The circuit breakers are designed to interrupt the maximum available fault current that could be present. Circuit breakers are usually either oil breakers or vacuum breakers. The type of breaker represents the medium used to extin- guish the arc created when opening the circuit breaker or closing under load conditions. A third medium, known as SF6, is another type of breaker that is fmding its way into the small hydro market. 4. Main Transformer The power generated must be transported to a distribution system through the transmission lines. Transformers are electrical devices that increase the output voltage from the genera- tor to match the voltage of the transmission line. Normally, transmission voltages are quite high to minimize electrical losses, whereas generator output voltages are low. Therefore, transformers are located close to the powerhouse. Transformers may be located indoors or Dead end structure Utility metering and protection Circuit breaker Main transformer 4-1 ASCEIEPRI Guides 1989 Bus work outdoors. Nonnally, the power-using utility specifies the type of transfonner and the inter- connection requirement between the transfonner and the utility transmission system. Transfonner losses are inversely proportional to the cost of the transfonner. S. Bus Work The substation structure, circuit breakers, main transfonner, and other miscellaneous sub- station equipment are electrically connected by using bus work The bus worlc is designed to carry the full load of the plant's system. The bus work is usually round copper bus, flat copper bus bar and, in some cases, ordinary copper wire. This bus work is installed and braced to withstand the forces created by fault currents that can occur on the system. Because the bus bar is usually installed uninsulated, careful consideration must be used in the design of the system to maintain proper distances between the conductors and ground. B. TRANSMISSION LINES The planning and design criteria for transmission lines are included in the volume on con- ventional hydro. The peculiarities for small hydro are primarily: 1. Utility intertie. In most cases, when a small hydro connects to the utility, it is con- necting to an infinite bus where the utility controls voltage and frequency. Often, a small hydro project is located in a remote area and connects to the utility distribution system. The stability, strength, and variations must be evaluated by an electrical engi- neer to have confidence of consistent power production. 2. Raptors. Many small hydro projects use transmission lines of less than 60,000 volts, in which case the conductor spacing must consider raptor proof requirements. See Chapter 4, ''Transmission Lines and Switchyards" of part C of the Conventional Guidelines. ASCE/EPRI Guides 1989 4-2 SMALL-SCALE HYDRO DIVISION III. CONSTRUCTION Chapter 1. Construction Contracts Chapter 2. Acceptance Tests ASCE/EPRI Guides 1989 CHAPTER 1. CONSTRUCTION CONTRACTS This chapter is under review. It will be available in January 1991. CHAPTER 2. ACCEPTANCE TESTS CONTENTS Section Page A. Standard test procedures ............................................................................................................................. 2-1 1. Efficiency ................................................................................................................................................ 2-1 2. Flow ........................................................................................................................................................ 2-1 a. Large flows ......................................................................................................................................... 2-1 b. Small flows ......................................................................................................................................... 2-2 3. Head ........................................................................................................................................................ 2-2 4. Output ..................................................................................................................................................... 2--4 5. Other Tests .............................................................................................................................................. 2--4 FIGURES Figure 2-1 Pressure tappings connected through ring main to pressure gauge ........................................................ 2-3 2-2 Pressure tapping ...................................................................................................................................... 2-3 The "Acceptance Tests" chapter was written by: Ray Toney, P.E. Ray Toney and Associates P.O. Box 1342 Redding, California 96099 CREDITS ASCE/EPRI Guides 1989 CHAPTER 2. ACCEPTANCE TESTS A. STANDARD TEST PROCEDURES The standard procedures for testing of hydroelectric equipment are included in the follow- ing documents: 1. International Code for Field Acceptance Test of Hydraulic Turbines, Publication 41, (IEC-41) International Electrotechnical Commission, 1963 2. Test Codefor Hydraulic Prime Movers, ASME Power Test Codes, American Society of Mechanical Engineers, New York, 1949 These two codes specify the details to accurately measure the efficiencies of the turbine and its components. 1. Efficiency For small hydro, most owners are interested in water-to-wire efficiencies. Water-to-wire is defmed as the efficiency developed from the net effective head of the plant as recorded on the powerhouse kilowatt meter. Usually it does not include switchyard losses or station power. It does, however, include turbine, generator, speed increaser, draft tube and switchgear. The measured efficiencies can be determined with careful measurement and normal testing conditions within ±1.0 to ±2.0 percent; however, for unfavorable conditions higher inaccuracies must be considered. 2. Flow Codes Water-to-wire efficiencies Aow must be accurately measured to determine the plant efficiency. If careful considera-Flow tion is given to flow measurement in the planning and design phase of the plant, flows can be measured to within ±1.5 percent accuracy at a reasonable cost. If flow measurement is not considered during design, it may be expensive to achieve even ± 5 percent accuracy. It is common after startup for a plant to be able to produce the maximum specified rated capacity, but in many cases this is accomplished by utilizing 10 to 15 percent more flow than specified in the warrantee. The reality of low efficiencies often becomes apparent when the plant is run at the 50 percent design flow point. Therefore, it is important to test the plant system efficiencies for a complete range of flow conditions. Depending upon the guaranteed efficiency curve, between three and five points between and including the mini- mum and maximum operating flows should be tested. IEC-41 outlines several common methods for measuring flow and their expected inaccura- cies. a. Large flows • Salt velocity method (±1.0%). In this method, a highly concentrated saltwater slug is injected into a penstock and the time is determined for its travel between two points. Large ftows 2-1 ASCE/EPRI Guides 1989 Small flows Head • Pressure-time (±1.0%). 'This method uses a pressure-time diagram developed at a JK)int or severalJK>ints on a penstock, created by the pressure wave created by closing of guide vanes or nozzle on the turbine. • Dilution (±1.5%). 'This method introduces a continuously known concentration solu- tion of chemicals at a steady rate into the conduit and measures the concentration downstream of the completely mixed solution to obtain the conduit flows. • Current meter (±1.5%). Current meters are placed in the closed or open conduit or channel to measure velocity patterns at a section. Also good for small flows. b. SmaUjlows • Weirs (±1.5%). 'This method uses known head discharge relationships over standard weirs to measure the flow. • Pi tot tubes ( 1.5% ). 'This method is used for closed conduits running full, whereby velocity is measured across the flow path integrated to obtain the total flow. • Orifices, nozzles, and venturimeters. These methods use differential pressures across an opening with a calibrated discharge coefficient usually provided by the sup- plier to compute the flow. • Current meters (1.5%). Current meters placed in an open, unifonn channel to deter- mine velocity pattern and integrate to total flow. IEC-41 outlines the procedures and criteria that must be followed for each method to ensure these levels of accuracy. 3. Head The gross head, as well as the effective head available to the turbine, should be measured. Accurate flow, water surface, and pressure readings will allow detennination of head loss versus flow curves for the trashracks, fish screens, and penstock draft tube. Surveyed benchmark. elevations accurate to 0.01 foot at the inlet works, inside the JK)werhouse, and at the tailrace will facilitate accurate head measurements. Water surface elevations can be made by JK>int-gauge measuring down from a datum or a staff gauge in stilling wells. Probable inaccuracies for measurements with a JK>int or float gauge are 1/h percent, where his the head of project in meters. If plate gauges or fixed scales are used, 5/h percent is acceptable. It is imJK)rtant that pressure gauges are installed properly and calibrated. /EC-41 lists recommendations for location and installation of pressure tappings. In small diameter pipes, two taps may be sufficient. On larger pipes, more taps should be used, such as shown on figure 2-1. The tap itself, shown on figure 2-2, is very imJK)rtant and may influence the pressure readings by as much as 20 percent. If done correctly, the pressure can be read with an accuracy of± 0.5 percent. ASCE/EPRI Guides 1989 2-2 a) P•Jr;:::, IJ) P~w-: ;:ug: C) Dr:in:~: Figure 2-1.-Pressure tappings connected through ring main to pressure gauge. ···dl; i; :~~.:·~ • I I • I // • "' .·~···. 't; t. / "~·· ~ -~;'. :.4 ............ . .. / ... ------..; / ... / . ·' . / .-"' 1' ·"/",/ .. ·,·· , .. .; ....... ",.,.,. , ·" · ,· ; ,. · l;r '/ ... · · · I _jd.~ d•J-5mm l:zd =5-TZ:nm r=dl4 Figure 2-2. -Pressure tapping. 2-3 ASCEIEPRI Guides 1989 The pressure gauge regardless of type should be calibrated at the site with a dead weight tester or the pressure read directly with a dead weight gauge. A few simple rules on measuring head can help in obtaining accurate measurements: l. Always check to make sure that the surveyed water surface elevations and the indi- cated static penstock pressure are in conformance prior to starting dynamic testing. 2. Account for velocity head at the gauge when computing head from pressure read- ings. 3. Make sure to flush out pressure lines from the penstock to the gauge before each reading. 4. Output Direct output from the turbine can be determined by using measurements of torque and speed to ±1.0 percent. Torque measuring equipment, such as dynamometers or torque cells are expensive and unless the original design considered the addition of such devices, they may be very difficult to add to a small hydro machine. Station power usages can be measured with clamps on ampere meters. Since water-to-wire efficiencies are usually all that is required, most power output mea- surements are from the terminals of the generator. For an ac generator, the probable inac- curacy of the measurement should be less than ±0.8 percent. Generally, factory generator test results can be relied on for field testing of the unit. If the factory generator tests are inaccurate, abnormal heating will occur in the windings or bearings. During each individual test, the head, flow, and load must remain constant. The gate or nozzle openings, headwater, tailwater, and blade or deflector settings must remain fixed during the test. Given the inaccuracy of the net head measurement (Ill), the inaccuracy of the flow (I:Q), and the inaccuracy of the power measurement (IP), the total inaccuracy of the plant (E) is: (2-1) For careful measurement and normal testing conditions, ±1.5 to ±2.5 percent can be obtained. S. Other Tests There are many other important tests that must be conducted before the owner accepts the plant. Most are electrical and mechanical. The general categories are listed here for refer- ence. • Normal startup and shutdown • Emergency shutdown • Protection equipment • Runaway protection ASCE/EPRI Guides 1989 2-4 • Stability tests • Support equipment perfonnance • Load rejection • Sustained runaway speed • Valve operating speeds 2-5 ASCEIEPRI Guides 1989