HomeMy WebLinkAboutTown Creek Hydroelectric Project (Akutan) 2011City of Akutan,
Alaska
Town Creek Hydroelectric
Project
Condition Assessment Report
Prepared for: City of Akutan
Prepared by: McMillen, LLC
EES Consulting Inc.
July 29, 2011
MCMILLEN, LLC
City of Akuran Town Creek Hydroelectric Project
TABLE OF CONTENTS
SectionI Introduction...................................................................................................................................1
1.0 Purpose ......... ---- ................. ................ ....... ................ ........ .... .....................
........ ............... .............I
1.1 Scope..................................................................................................................................................1
1.2 Modifications to Scope......................................................................................................................2
Section 2 Project Features and Operation....................................................................................................3
2.0 Introduction........................................................................................................................................
3
2.1 Document Review.... ........................... ....... . .......... . . ........... . ....... ..
. ... ........ . . .... ..... . 3
2.2 History
3
2.3 Project Description.............................................................................................................................4
2.3.1 Main Impoundment Dam and Reservoir............................................................................................4
2.3.2 Diversion Structures...........................................................................................................................5
2.3.3 Penstock.............................................................................................................................................5
2.3.4 Powerhouse........................................................................................................................................5
2.3.5 Instrumentation..................................................................................................................................6
2.4 Historical Energy Production information .........................................................................................6
2.5 Interviews...........................................................................................................................................
7
Section 3Existing System Assessment..........................................................................................................8
3.0 Introduction........................................................................................................................................
8
3.1 Investigations.....................................................................................................................................
8
3.1.1 Field Investigations............................................................................................................................8
3.1.2 Past Studies and Correspondence.......................................................................................................8
3.1.3 Dam Safety Report and Periodic Safety Inspection...........................................................................9
3.2 Acecss/Security..................................................................................................................................9
3.3 Diversion Dams..................................................................................................................................9
3.4 Main Impoundment Dam...................................................................................................................9
3.4.1 Intake Works......................................................................................................................................9
3.4.2 Reservoir..........................................................................................................................................
10
3A.3 Upstream Slope................................................................................................................................
10
3.4.4 Crest.................................................................................................................................................
10
3.4.5 Downstream Slope...........................................................................................................................
10
3.4.6 Abutments/Toe.................................................................................................................................
10
3.4.7 Spillway...........................................................................................................................................
10
3.4.8 Drains...............................................................................................................................................
10
3.4.9 Downstream Channel.......................................................................................................................
11
3.4.10 Penstock...........................................................................................................................................
It
3.4.11 Outlet Works....................................................................................................................................
11
3.4.12 Powerhouse......................................................................................................................................
11
3.4.13 Instrumentation................................................................................................................................
11
3.5 Penstock Headloss............................................................................................................................
11
3.6 Documentation of Procedures... ........................................................................
.............................. 13
Section 4Recommended System Improvements........................................................................................
14
4.0 Introduction......................................................................................................................................
14
4.1 System Improvements......................................................................................................................
14
4.1.1 Access..............................................................................................................................................
15
4.1.2 Diversion Dams................................................................................................................................
15
4.1.3 Main Impoundment Dam.................................................................................................................
15
4.1.4 Intake Works....................................................................................................................................
16
4.1.5 Reservoir..........................................................................................................................................
16
Pagel July 29, 2011
City of Akutan Town Creek Hydroelectric Project
4.1.6 Upstream Slope .......................................................
4.1.7 Crest........................................................................
4.1.8 Downstream Slope ..................................................
4.1.9 Abutments/foe........................................................
4.1.10 Spillway..................................................................
4.1.11 Drains......................................................................
4.1.12 Downstream Channel ..............................................
4.1.13 Penstock..................................................................
4.1.14 Outlet Works... .......................................................
4.1.15 Powerhouse / Turbine .............................................
4.1.16 Instrumentation......................................................
4.1.17 Documentation of Procedures ................................
4.2 Cost Estimates........................................................
Section 5 Findings, Conclusions, And Recommendations
5.0 Findings..................................................................
5.1 Conclusions............................................................
5.2 Recommendations..................................................
LIST OF TABLES
16
16
16
16
17
17
17
18
18
18
18
18
18
20
20
20
20
Table 3-1. Penstock Hydraulic Loss Parameters ................... ___ .............................................................. 12
Table 3-2. Summary of Existing Town Creek System Assessment............................................................ 12
Table 4-1. Summary of Existing Town Creek System Improvements and Costs ......... ............................. 19
APPENDICES
Appendix A
Photographs
Appendix B
Cost Estimates
Appendix C
As -Constructed Drawings
Appendix D
Field Trip Report
Appendix E
Dam Safety Report and Periodic Safety Inspection
Condition Assessment Repon
Page ii
July 29, 2011
City ofAkumn Town Creek Hydroelectric Project
SECTION 1
INTRODUCTION
1.0 Purpose
McMillen, LLC (McMillen) and EES Consulting Inc. (EESC) prepared this report to summarize
the field investigation, assessment and recommendations for the City of Akutan (City), Alaska
to complete the repairs and upgrade to the Town Creek Hydroelectric project necessary to return
the hydroelectric project to operation.
1.1 Scope
Electric Power Systems (EPS) contracted with EESC and McMillen to complete an assessment
of the existing Town Creek Hydroelectric project, determine the required repairs and upgrades,
and develop cost estimates for completing the identified work elements. The scope of work for
the Town Creek Hydroelectric Project includes the following elements:
• Task 1—Data Collection and Review: Gather and review available existing data,
reports, designs and drawings related to the Town Creek Hydroelectric Project. Sources
may include Alaska Energy Authority, the City, EPS project files and the internet.
Interview the City management and staff as required.
• Task 2 — Field Investigation/Inspection: Mobilize to Akutan to tour and inspect the
hydroelectric project. A visual inspection and engineering survey of the hydroelectric
components and features wilt include:
• Main impoundment dam and reservoir
• Diversion structures
• Penstocks
• Gates, screens, valves and other appurtenances
• Powerhouse, to include diesel Human -Machine Interface (HMI), hydro HMI,
diesel and hydro PLC and controls, communications and switchgear
• All other existing components and features of the hydroelectric system pertinent
to the operation of the system for power production or structural integrity
Gather and evaluate all information necessary to calculate friction and head losses in the
penstock. All findings and calculations will be included in the project report.
• Task 3 — System Drawings: Based on data and information collected during the field
investigation and inspection of the system, prepare drawings of the existing facilities.
The drawings will contain line, grades and locations as measured in the field. Reservoir
pool shapes, volumes and underground construction are not depicted in these drawings.
Task 4 — Dam Safety Assessment and Permitting: Conduct a detailed visual
inspection and engineering survey of the primary dam and reservoir to determine general
condition, current operability, structural integrity and stability. Conduct visual inspection
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City of Altman Town Creek Hydroelecyic Project
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^ of the adjacent soils at the dam site. Prepare a written assessment of the dam and
reservoir compliance with recognized safety practices and State of Alaska Dam Safety
^ Program. Coordinate with the State of Alaska Dam Safety Office to determine if
^ upgrades or repairs are needed to comply with pertinent State laws and regulations.
Prepare a dam safety permitting requirements checklist to be included in the project
report.
• Task 5 — Project Reports:
Draft Preliminary Field Report and Engineer's Estimate: Based on information
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gathered during the document review and field investigation, a draft preliminary
report of findings and recommendations will be prepared. The report will be of
sufficient detail and substance to support a City of Akutan Round III renewable
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energy grant that will be submitted to the Alaska Energy Authority. The final content
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of the report will be coordinated with the City, RMA Consulting Group (RMA) and
the Alaska Energy Authority grant administrator.
Final Preliminary Report: The final preliminary report will be expanded to a report of
final design and recommended actions necessary for repair and upgrades to the Town
Creek Hydroelectric Project. The final report will include a system design, materials
lists, cost estimates and a summary of actions required for permitting and compliance.
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Final Dam Safety Report: The final dam safety report will be expanded to a report of
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final design and recommended actions necessary for repair and upgrades to the Town
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Creek Hydroelectric Project. The final report will include a system design, materials
lists, cost estimates and a summary of actions required for permitting and dam safety
compliance.
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1.2 Modifications to Scope
During the course of the project, several modifications were made to the original scope. Several
new tasks were added as the result of increased budget allocations. These modifications
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included the following:
• Due to snow cover and weather conditions during the field data collection site visit, an
r^ additional site visit to Akutan was authorized and conducted.
• In the absence of existing as -built drawings for the Town Creek Hydro system, additional
fieldwork and engineering support were required to complete an as -constructed drawing
set.
• After startup of the project, the City of Akutan received a Notice to Dam Owners from
^, the Department of Natural Resources Dam Safety Office, informing the City of the need
to conduct a Periodic Safety Inspection (PSI). The requirements of the PSI were
substantially greater than the Dam Safety Report and the Alaska Dam Safety Program
Inspection Checklist called for in the original scope of the project. This additional work
r, was authorized and completed as part of the final condition assessment.
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City of Akutan Town Creek Hydroeleetne Proieel
SECTION 2
PROJECT FEATURES AND OPERATION
2.0 Introduction
Section 2 presents the documents reviewed, history, specific features of the project, and
operation related to the Town Creek Hydroelectric Project.
2.1 Document Review
A review of available documents pertaining to the project was performed prior to visiting the
site. This review helped direct the focus of the field investigation to specific areas of the
hydroelectric project. These documents included:
• EPS, City of Akutan Hydro Inspection Report & Upgrade Cost Estimates, May 2003.
• Grant Application of Akutan Hydroelectric System Repair, City of Akutan, Renewable
Energy Fund Grant Application, AEA-09-004, September 3, 2008.
• Alaska Power Systems, Alaska Science and Technology Foundation (ASTF) Grant
Agreement 92-4-277, Unitized Village Scale Hydro -diesel Generation System, April
1994.
• Akutan Hydropower Feasibility Study, HDR/On Water Engineers and Dryen & LaRue,
1989;
• Akutan Hydropower, Preliminary Design Report, Ott Water Engineers, 1980.
• Egor Eispov, LCMF Inc., Alaska Energy Authority, Akutan Rural Power System
Upgrade, 2007.
2.2 History
The Akutan Town Creek Hydro Dam and power system was constructed by Alaska Power
Systems (APS). The City and APS entered into ajoint venture named Akutan Hydro Joint
Venture. Little is known concerning construction means and methods, compaction test results,
depth to bedrock or inspection. The external configuration does generally reflect the figures
found in Ott Water Engineers Preliminary Design Report, 1980 and other reports include a dam
cross section prepared by Shannon and Wilson. According to the City, more complete
construction records were confiscated in a bankruptcy dispute by a bank.
There is limited documentation of the construction of the main impoundment dam, diversion
dams and penstock in the above referenced documents. However, based on a review of the
available correspondence, construction was completed in 1993. Especially important in
documenting this are the two letters from John S. Thiede, Project Review Coordinator, Alaska
Office of Management and Budget Division of Governmental Coordination.
The ASTF Grant Agreement contained information on the original powerhouse equipment, but
does not reflect the current equipment arrangement. The documents reviewed included
conceptual dam design information performed by Shannon & Wilson. This information is more
schematic in nature with respect to the dams and does not show the location of the intake
Assessment Report
July 29, 2011
^- CityofAkuW Town Creek Hydroelectric Pmiecl
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screens, penstock and valves, and related equipment. Photographs of the site are located in
Appendix A but only contain inspection photographs over the last 2 years. No construction
,... photographs were found.
2.3 Project Description
r. The Town Creek Hydro Dam components and features include:
. Main impoundment dam and reservoir
. Diversion structures
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. Penstocks
. Hydroelectric Components
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These features are described in greater detail below.
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2.3.1 Main Impoundment Dam and Reservoir
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ell
The main impoundment dam is located at approximately 800 feet above mean sea level (amsl).
The dam is located within a small basin that is formed by the surrounding ridges and a flat
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valley. The approximate size of the reservoir is 1.7 acres. The entire Town Creek watershed
basins total approximately 410 acres. However, the watershed area above the main
impoundment is much smaller, on the order of 20 acres. Drawings 3 through 5 provide
schematic illustrations of the dam and surrounding area.
The dam consists of compacted earth fill with a cutoff wall of polyvinyl chloride (PVC) sheetpile
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wall that was placed on a timber foundation installed in an excavated area of the existing stream.
An impermeable liner was placed on the upstream side of the sheetpile wall and drainage fabric
was placed on the downstream side to collect seepage water. A perforated pipe is installed at the
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downstream base to collect seepage and transport it to the toe of the dam. Compacted earth
embankments were placed on both sides of the sheetpile for support. Rock ripmp was placed on
the face of the slope to prevent erosion. The dam is approximately 20 feet high, 200 feet long
and 12 feet wide at the crest.
The spillway is located at the top of the dam and consists of three, 10-inch diameter high density
polyethylene (HDPE) pipes. The openings to the spillways are not screened and are subject to
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clogging from debris and ice (however, there is no evidence that this happened on the main
impoundment). There are no shutoff valves or covers associated with the spillway. The outlet of
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the spillway is at the toe of the dam with rock placed near the outlet to dissipate energy.
The intake to the penstock is estimated to be located approximately 8 feet below the Poll pool
level of the reservoir. The penstock intake may be sluiced by opening a valve on a tee or Wye
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that discharges flow and sediment back to Town Creek. There is an additional 10-inch HDPE
pipe that outlets next to the three spillway pipes. The function of that pipe is unknown. There is a
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drain pipe right next to it so it is uncertain whether this is another drain pipe or if this pipe
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represents the outlet for a low flow conduit.
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City of Akutun Town Creek Hydroelectric Project
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2.3.2 Diversion Structures
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Three small diversion dams are located in streams adjacent to the main impoundment dam
(Drawing 3, Appendix Q. These diversion dams transfer water to the main impoundment
reservoir. Each dam is approximately 5 feet tall and has a 10 feet wide crest. The dam surfaces
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are covered with rock gabions shaped to allow excess water flow over the dam. Geotextile is
placed under the gabion baskets. Water from the western diversion dam flows into a 6-inch
HDPE pipe to the Town Creek Hydro Dam reservoir. Water from the east diversion dam flows
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through a 6-inch HDPE pipe to the Town Creek Hydropower Dam reservoir as well. Each of the
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three small diversion dams has an unscreened intake and a butterfly valve is located immediately
downstream of each of the intakes to control water flow from the diversion dams. A 10-inch
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HDPE pipe spillway is located at the top of each of the diversion dams and extends to the toe of
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the dam. Most of the water that supplies the main impoundment is supplied by the three
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diversion dams. Photos of several of these diversion features are in Appendix A (photographs
26-30).
2.3.3 Penstock
The penstock from the main dam (approximate dam toe elevation 800 feet amid is a ] 0-inch
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HDPE within the dam cross-section with anchored steel pipe down slope from the dam. The
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pipe is approximately 3,300 feet long, dropping approximately 765 vertical feet to the
powerhouse. The location of the penstock is illustrated in Drawing 3 (Appendix Q. The
penstock has three valves: the first two located immediately downstream of the intake and the
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third immediately upstream of the powerhouse. The first valve is a shutoff valve; the second
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valve is used for sluicing sediment from the penstock. The third valve, at the powerhouse, is a
final shutoff valve.
2.3.4 Powerhouse
The powerhouse was originally equipped with a hydro turbine -generator connected to a small
clutch -operated diesel engine. The existing diesel generator only operates when the hydropower
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unit was not operational. This diesel -hydro generator system was reconfigured at an unknown
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date and the system now has a separate diesel -engine generator system. The original diesel
generator had a rating of 150 kilowatt (kW) and was not operated on a continuous basis. The
diesel -hydro system (DHS) control has experienced significant issues in the past and the hydro
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portion of the generation system is not operating consistently. Drawings of the original
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powerhouse configuration are presented in Drawing 8.
The hydro turbine is a Pelton-type double runner with double nozzle hydraulic control
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manufactured by Canyon Hydro, rated at 150 kW with a hydraulic head of 685 feet and 3.5 cubic
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feet per second (cfs) discharge. However, the hydro turbine is only capable of peaking at 105
kW. The deflectors are hydraulically operated with a counterweight for emergency operation.
The needles are also hydraulically operated with limit switches to indicate open/close
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positioning. The 10-inch penstock pipe is necked down to an 8-inch pipe before the shutoff
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valve. The hand -operated shutoff valve is an 8-inch 300 pounds -per -square -inch (psi) gate valve
and is located outside of the powerhouse.
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Condition Assessment Report Pose 5 July 29, 2011
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City of Akuoo Town Creek Hydroelectric Pmimt
The hydro turbine is connected through a flexible coupling to a 1,800 revolutions per minute
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(rpm) synchronous generator rated at 140 kW, 0.8 power factor that produces power at 480 volts
(V). The hydro turbine generator uses a Thomson & Howe control system. This system utilizes
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a load bank for regulation of frequency, allowing rapid response to changes in system load.
Thomson & Howe also supplied the small hydraulic power units for the needle valves and
deflectors.
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2.3.5 Instrumentation
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A pressure transducer is located in the main impoundment dam to monitor water level within the
reservoir. The powerhouse control system is connected to this pressure transducer and when the
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water level drops below a pre-set level in the reservoir, the hydro system ceases operation and
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the diesel engine starts producing power. Due to significant problems in the past, the pressure
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transducer faded and the powerhouse control system is currently not often used. The pressure
transducer is submerged in sediment and records of use are insufficient to provide additional
detail.
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A Supervisory Control and Data Acquisition (SCADA) system was originally installed at the
powerhouse to monitor the system remotely. This system monitored high -low reservoir water
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level, high engine water temperature, crankcase oil pressure, exhaust gas temperature and speed
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(rpm) for a single DHS unit. The SCADA system also allowed adjustment of control parameters
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and alarms. The current system has been modified from the original configuration. The actual
configuration and capability of the hydro instrumentation system is unknown.
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During the site visit with EESC and EMA, the Mayor attempted to put the hydro unit on-line.
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The unit began to spin, came up to synchronous speed, closed in and loaded up to 10 kW.
Shortly thereafter, the unit tripped off. According to the HMI, there was no alarm indicating
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why the unit tripped off-line. The HMI indicated a penstock pressure of 331 psi when the unit
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was off-line. As noted previously, the main dam level sensor is not functioning so there is no
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way to monitor the reservoir level at the main dam.
The HMI system for control and monitoring of the diesel -hydro powerhouse was inspected. The
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Mayor demonstrated the HMI system, which uses a desktop personal computer (PC) located at
City Hall. This is the new HMI system, which was developed and installed by EPS. The diesel
gen-set was producing 80 kW at 490 V on October 26, 2009 at 17:00.
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2A Historical Energy Production Information
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Historical energy production records were obtained from the Alaska Energy Authority Power
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Cost Equalization program from 1999 to 2009. City energy production in the late 1980's, and
power plant log sheets. A review of this information indicates that there has been very limited
hydro operation over the past 10 yens. The average annual production from 1999 to 2009 was
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538,000 kilowatt hours (kWh), this includes both diesel and hydro production. The annual
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energy production has been increasing over the last 20 years with energy production of 305,000
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kWh in 1989 to 566,000 kWh in 2009. The energy consumption for Akutan has nearly doubled
in the last 20 years.
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Condition Assessment Report Page 6 July 29, 2011
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^ City of Aimum Town Cr k Hydrmlecoic Project
2.5 Interviews
r. The project team met with the City's Mayor Joe Bereskin and Demetri Tcheripanoff to discuss
the Town Creek Hydroelectric Project history. The original hydroelectric project was designed
r' and constructed by APS in 1990. However, APS went bankrupt and the City was not able to
r' obtain any project documentation aside from what was contained in the final report for the ASTF
r, grant and limited Operation and Maintenance manuals. According to Mayor Bereskin, APS
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equipment was "home-made" and not very reliable.
The City has experienced problems with sediment clogging the intakes at the diversion dams and
the main impoundment dam. These intakes are located underwater with no easy way to clean
them due to lack of a cleaning system or access. The intake screens, if existing, also become
^ clogged with organic debris.
Neither Mayor Bereskin nor Mr. Tcheripanoff could provide information on the construction of
the main impoundment dam and diversion dams. However, they did note that APS brought in a
dozer and backhoe for construction and had been able to get the equipment up to the upper
r watershed via a temporary construction road. When asked about construction of an access road
^ to facilitate operation and maintenance of the dams, the Mayor noted that the soils are very
erodible and the residents would not want to see an ugly road from the town. (Note: on
r" September 8, 2010, the Mayor informed McMillen that the City is requesting a permanent access
road that will not erode and that this road is acceptable to the town residents).
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The project team inquired regarding the stems of the Town Creek Hydro Project and the Alaska
^ Department of Dam Safety. Mayor Bereskin noted that a representative from the Alaska
Department of Dam Safety had visited the site and concluded that the main impoundment dam is
r subject to state regulation due to its height.
According to City staff, the hydro turbine runs well but is not presently being used because of the
.- failure of the main impoundment dam level sensor. The Mayor noted that the control system
A, seems overly complex and is difficult for them to troubleshoot problems. The recent
improvements by EPS were helpful as new components are off the shelf as opposed to custom
built equipment as was originally supplied by APS. The Mayor noted the difficulty for the City
to properly operate a hydro project with local residents due to the system complexity.
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"^ Condition Assessment Report Page 7 July 29. 2011
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City ofAkutan Town C®ek Hydroelectric Project
SECTION 3
EXISTING SYSTEM ASSESSMENT
3.0 Introduction
Section 3 presents the results of the condition assessment of the existing Town Creek
Hydroelectric Project.
3.1 Investigations
An assessment of the existing system was completed using a combination of field investigations,
interviews with City of Akutan staff, review of past studies and correspondence, and completion
of a Periodic Safety Inspection (PSI) of the existing Town Creek Dam. A brief description of
these documents is presented in the following paragraphs.
3.1.1 Field Investigations
On October 23, 2009, representatives from EESC, McMillen, and RMA performed the initial
field investigation. The project team hiked into the Town Creek watershed following the
penstock route on October 24, 2009 and observed the main impoundment dam, the three
diversion dams, the penstock and the powerhouse. The upper part of the watershed had up to 18
inches of snow on the ground; thus, preventing complete assessment of dam conditions. The
main impoundment dam and the three diversion dams were inspected. Due to the presence of 18
inches of snow, not all of the items required for a dam safety inspection were able to be
examined or identified in the field during this investigation. A preliminary assessment of the
existing hydroelectric project was completed and summarized in a field trip report dated October
2009 (see Appendix D).
McMillen visited the site again on September 8 and 9, 2010 to collect information about the dam
without snow cover. The McMillen project team hiked into the Town Creek watershed
following the penstock route, and measured slopes and distances at the main impoundment dam.
The three diversion dam crest and toe elevations were also measured. The main impoundment
dam and the three diversion dams were inspected. Photographs of the dams from both the 2009
and 2010 site visits are located in Appendix A. Based on the 2009 and 2010 site visits and
inspections, a PSI was completed as discussed in paragraph 3.1.3.
3.1.2 Past Studies and Correspondence
A review of available documents pertaining to the project was completed prior to visiting the
site. These documents provided the history of the project development and allowed the field
investigations to focus on specific areas of the hydroelectric facility. These project documents
are summarized in paragraph 2.1 of this report.
Condition Assessment Report Page 8 My 29. 2011
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City of Akuum Toum Creek Hydroelectric Project
3.1.3 Dam Safety Report and Periodic Safety Inspection
McMillen completed an extensive Dam Safety Report, including the Alaska Dam Safety
Program Inspection Checklist. The report determined that the Town Creek Hydro dam is under
the jurisdiction of the Alaska Department of Natural Resources Dam Safety Program (I 1 AAC
93), with a Class II hazard potential. Significant items noted in the report were: potential hazard
to downstream infrastructure (school and water treatment facility), and uncontrolled seepage near
the toe of the abutment areas. These findings, in conjunction with the January 2010 notice to the
City of Akman requiring a periodic safety inspection for the Town Creek Hydro dam, resulted in
the Periodic Safety Inspection, Akutan Town Creek Hydra Dam, as approved by the Alaska Dam
Safety office, June 2011 (Appendix E).
3.2 Access/Security
Access to the existing dam and components is available only by foot. When the ground is clear
of snow, a primitive trail is available that leads up to the main impoundment dam and diversion
dams from the town. There are currently no security measures in place. Due to the remote
location of the dam, primitive trail system, and potential safety issues, access to the dam is
considered POOR and requires upgrades. Security is considered FAIR due to the remoteness
and overall size and scope of the facility (a small remote facility).
3.3 Diversion Dams
Overall, all three diversion dams were considered to be in POOR condition due to silt
accumulation, lack of screening on the pipe intake and spillway, and evidence of overtopping
and erosion on the downstream face.
3.4 Main Impoundment Dam
An inspection of the main impoundment dam indicated that the dam experiences uncontrolled
seepage, the sheetpile cap requires replacement and the spillway which consists of a battery of
three pipes has no system to stop potential clogging with debris. Each of these issues is
discussed in more detail in the following paragraphs. Due to these issues, the main
impoundment dam is considered to be in POOR condition.
3.4.1 Intake Works
The penstock intake consists of a 10-inch diameter HDPE pipe submerged below the water
surface. The intake was not observable during the field investigation due to the water depth in
the reservoir. It was assumed that there is no screen on the penstock intake due to the amount of
debris found in the needle (spear) valves. 'Be lack of screening results in a POOR rating for the
intake.
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City of Akutan Town Creek Hydroelectric Project
3.4.2 Reservoir
A large erosion area was observed on the east side of the reservoir. Sediment accumulation was
also evident within the reservoir, though adequate dead storage appears to be available. The
reservoir is considered to be in FAIR condition.
3.4.3 Upstream Slope
The upstream face is protected with rock riprap, constructed at a mild slope, and is considered to
be in SATISFACTORY condition.
3.4.4 Crest
The existing pile cap is damaged and a gravel surface placed on the existing access road. The
crest is considered to be in FAIR condition due to the damage to the pile cap and lack of
surfacing on the access road.
3.4.5 Downstream Slope
The downstream slope is considered to be in SATISFACTORY condition due to the absence of
woody vegetation and no evidence of slope movement or erosion.
3.4.6 Abutments/Toe
Based on the field inspection, it appears that 0.5 to 1.0 efs is leaking through the toe new the
abutment areas; however no erosion is evident. The water is flowing through the riprap
protecting the abutments. The seepage water is clear. The abutments and toe are considered to
be in POOR conditions because of the seepage, otherwise they are in SATISFACTORY,
condition.
3.4.7 Spillway
The spillway was determined to have adequate capacity for a 100 year now event, but has no
protection for debris or freezing of the pipe entrance. Furthermore, the pipes are arranged as a
battery of three pipes that would promote debris clogging or ice clogging. Since the pipes
protrude horizontally above the water surface, they would attract floating debris and ice. The
project team noted concern about the potential for overtopping the dam if the pipes become
frozen and the auxiliary/emergency spillway was blocked due to snow and/or ice. The dam may
overtop and fail if there was a rain on snow event while these pipes were obstructed and the
auxiliary/emergency spillway was obstructed with snow, ice, or debris. Therefore, the spillway
was assumed to be in UNSATISFACTORY condition.
3.4.8 Drains
The drainage system appears to consist of a combination of drainage mat downstream from the
sheetpile and a collection system with a corrugated six-inch pipe and possibly a 10 inch HOPE
pipe. Flow was passing through the CMP pipe during the September 2010 visit. However, there
Condition Assessment Report Page 10
City of Akulm Town Crak Hydroelectric Pmjmt
was significant uncontrolled seepage estimated at 0.5 to 1.0 cfs as well. The use of a drainage
mat rather than a granular filter is not currently accepted technology. The sub drain outlet is
considered to be in POOR conditions due to the uncontrolled seepage.
3.4.9 Downstream Channel
The downstream channel is in good condition except where the overland flow has re-entered the
channel, causing moderate erosion. The downstream channel is considered to be in FAIR
condition.
3.4.10 Penstock
The penstock is approximately 3,300 feet long extending from the main impoundment dam to the
powerhouse located in town. The pipe is completely buried and no signs of erosion or sinkholes
were observed in the area of the pipe. The penstock shutoff valve and the sluice valve on the
main impoundment dam were not able to be shut off during the field investigation. The Mayor
confirmed that they were able to exercise these valves during a subsequent inspection and
operation attempt. A camera inspection would be required to determine the interior pipe
condition. The penstock is considered to be in POOR condition due to the unreliable nature of
these valves.
3.4.11 Outlet Works
The outlet is an open ditch leading from the Pelton Wheel Turbine back to Town Creek. It is
controlled via the needle valves in the powerhouse. The outlet was noted to be in
SATISFACTORY condition.
3.4.12 Powerhouse
The turbine, generator, and powerhouse building were considered to be in SATISFACTORY
condition.
3.4.13 Instrumentation
The hydro turbine was not operating at the time of the inspection due to a failure in the reservoir
level monitoring system. The pressure transducer located at the dam used to measure water level
is currently non -operational. A new water level sensor was installed on November 26, 2010 at
the reservoir. Resistance measurements were recorded at the powerhouse which indicated very
high/open resistance (4 Meg ohm) on the two wires attached to the probe. The wire from the
reservoir to the powerhouse was reported to have been accidently dug up at one point. Based on
the measurements taken at the powerhouse, it appears that the wire may have been damaged. For
this reason, the instrumentation at the powerhouse is in POOR condition.
3.5 Penstock Headless
As part of the overall system assessment, the headless within the existing penstock was
estimated. The frictional losses in the penstock were based on the following:
A -
Condition Assessment Report Page 1 I July
r
ofAkutan Toxin Creek
Table 3-1. Penstock Hydraulic Loss Parameters
Item
value
Main impoundment dam
water surface elevation
800 ft above ms1
Turbine matter elevation
26 ft above msl
Penstock length
3,300 ft
Penstock diameter
10 in
Penstock material
HDPE
Turbine maximum discharge
3.5 cfs
As part of the field investigations, the team was able to confirm the 10 inch diameter HDPE pipe
material at the powerhouse just upstream from the outdoor isolation valve. Standard HDPE pipe
is available in a range of pressure class ratings. The calculated gross head is 776 feet or 335 psi.
A HDPE pipe with a diameter to wall thickness of 7.3 has a pressure rating of 320 psi which is
the likely pipe pressure rating used at Town Creek. A lower pressure rating may have been used
in the upper reaches of the penstock, though no documentation is available to confirm this
assumption. Using the values listed above, the calculated head loss at full load is estimated at 64
feet. The resulting net head would be approximately 710 feet. This value is consistent with the
information provided by the turbine manufacturer, Canyon Hydro, which indicated the turbine is
designed for 685 feet of net head and a flow rate of 3.5 efs.
Table 3-2. Summary of Existing Town Creek System Assessment
Item
Section
Description
Assessment
Reference
Action
No,
Document
1
3.2
Access/Security
Poor
PSI, para. 6.1
Improve access and
security
2
3.3
Diversion Dams
Poor
PSI, para. 6.2
Address silt accumulation
3
3.4
Main
Poor
PSI, para 6.3
Address seepage, spillway
Impoundment
Dam
4
3.4.1
Intake Works
Poor
PSI, parr. 6.3.1
Address debris entering the
penstock
5
3.4.2
Reservoir
Fair
PSI, para. 6.3.2
No action re uired
6
3.4.3
Upstream Sloe
Satisfactory
PSI, part. 6.3.3
No action required
7
3.4.4
Crest
Fair
PSI, pars. 6.3.4
Repair damaged sheetpile
and access road
8
3.4.5
Downstream
Satisfactory
PSI, para. 6.3.5
No action required
Slope
9
3.4.6
Abutments/Toe
Satisfactory
PSI, para. 6.3.6
No action required
10
3.4.7
Spillway
Unsatisfactory
PSI, pain. 6.3.7
Address potential debris
and ice blockage of
spillway I e5
11
3.4.8
Drains
Poor
PSI, para. 6.3.8
Address seepage
12
3.4.9
Downstream
Far
PSI, para. 6.3.9
Repair channel erosion
Charnel
13
3.4,10
Penstock
Poor
PSI, pars.
Repair valves, complete
6.3.10
camera inspection of
penstock
Condition Assessment scpon Page 12
City ofAkutan Town Creek Hydroelectric Pmjecl
Item
Section
Description
Assessment
Reference
Document
Action
No.
14
3.4.11
Outlet works
Satisfactory
PSI, Para.
No action required
6.3.11
15
3.4.12
Powerhouse
Satisfactory
PSI, Pam.
No action required
6.3.12, 2009
Field Trip
Report
16
3.4.13
Instrumentation
Poor
PSI, para.
Replace cable from
6.3.13, 2009
powerhouse to reservoir
Field Trip
Re rt
3.6 Documentation of Procedures
A general review of the operations, maintenance, and monitoring plans was performed. Limited
data was available related to documented procedures. Overall, the following ratings were
identified:
• Operating procedures were not available resulting in an UNSATISFACTORY rating.
• Monitoring data was not available resulting in an UNSATISFACTORY rating.
• Maintenance procedures were not available resulting in an UNSATISFACTORY rating.
• Emergency action plan was not available resulting man UNSATISFACTORY rating.
Condition Assessment Report
Page 13
City of Akman Town Creek Hydroelectric Project
SECTION 4
RECOMMENDED SYSTEM IMPROVEMENTS
n
4.0 Introduction
McMillen completed a Draft Preliminary Field Report and Engineer's Estimate for the Town
Creek project in October, 2009. This report was used to support the City of Akutan's (Round
Ill) grant application (#469) as submitted to Alaska Energy Authority (AEA) in November,
2009. The grant request was approved and funds were appropriated under the Alaska Renewable
Energy Grant Fund program, for final design and construction of necessary repairs and upgrades.
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Based on the Final Preliminary Field Report and Dam Safety Report, AEA determined it would
be inappropriate to authorize the commitment of (Round III) funds for design and construction,
without a complete Periodic Safety Inspection. As a result, McMillen's efforts were directed
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toward coordination with the DNR Dam Safety Office, completion of the Periodic Safety
Inspection (Appendix E), and recommendations and cost estimates for system improvements
required to obtain certificate(s) to repair, modify or construct a dam.
r,
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Section 4 presents the system improvements required to return the existing Town Creek
e-.
Hydroelectric Project to reliable operation, including conformance with the findings and
recommendations of the approved Periodic Safety Inspection.
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4.1 System Improvements
r
As outlined in Section 3, an assessment of the existing Town Creek Hydroelectric system was
conducted to determine the actions required to return the hydroelectric facility to reliable
r'+
operation. The assessment identified capital improvements to the facilities required to address
system deficiencies as well as completion of the required documentation to meet the Alaska Dam
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Safety requirements, outline operation and maintenance procedures, and provide more reliable
data on the existing system.
Overall these system improvements are relatively straight forward and simple to implement. The
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one exception is the seepage issue associated with the main impoundment dam. As indicated in
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the PSI, seepage estimated between 0.5 and 1 cfs has been observed at the base of the dam. This
level of seepage has two potential significant issues. The first is lost generation. A loss of 0.5 to
I cfs from the penstock intake represents 14 to 28 percent of the powerhouse design flow which
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impacts the amount of energy available to the City. The second issue is long term stability of the
l"
dam structure itself. Since no as-builtinformation or construction photos we available for the
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existing main impoundment dam, the source and extent of the observed leakage is not known.
Continued uncontrolled seepage could accelerate with time resulting in migration of fines and
loss of the dam integrity. Of all the system improvements outlined in the following paragraphs,
characterizing and controlling the identified seepage is the most challenging and critical for the
,...
long term operation of the Town Creek Hydroelectric project.
A brief description of the recommended system improvements associated with each of the
i-
existing system components is presented in the following paragraphs.
�`
Condition Assessment Report Page 14 July 29, 2011
City ofAlrai n Town Creek Hydroelechic Project
4.1.1 Access
In order to properly operate and maintain the dams in the upper watershed, reliable access is
required. An access road with reasonable grades would allow all -terrain vehicle (ATV) access
year-round. The road would consist of using gravel from the harbor with cellular confinement
r- material (grid) or geotextile to form a base and sides where the trail cuts through ridges.
Vegetation would be reestablished to maintain low visibility of the trail from town. Overall,
security is considered satisfactory due to the remote location of the dams. It is recommended
that locks be installed on the gate operators to prevent unintended operation. Consideration may
be needed to the future acquisition, if required, of an ATV that is suitable for climbing, is all-
weather capable with tire chains, etc. to provide access to the site.
^' 4.1.2 Diversion Dams
All three diversion dams were considered to be in poor condition due to silt accumulation, lack
^ of screening on the pipe intake and spillway, and evidence of overtopping and erosion on the
r downstream face. Repairs and improvements recommended to address these issues include:
el
a)
Excavate sediment out of the bottom of the reservoirs (— 50 cy each).
e—
b)
Compact fill around the scoured areas at each dam crest.
e—
c)
Replace the pressure treated wood sheetpile protection at West Diversion Dam
e-
d)
number 1.
Install small trashracks at the intake on the three diversion dams (8 feet by 3 feet
horizontal trashracks).
F+
e)
Install sediment sluice pipes through the vinyl sheet piling on the three diversion
^
dams. Backfill and replace slope protection.
^
4.1.3 Main Impoundment Dam
Repair/replacement and modifications to the main impoundment dam and the diversion dams in
^
the upper watershed are required to maximize water capture and system reliability. These
^
modifications include:
^
1. Excavate sediment out of the bottom of the reservoir.
2. Replace all three valves on the penstock consisting of two 10-inch valves at the dam
�^
and one 8-inch valve at the powerhouse.
3. Install insulated 6 feet diameter corrugated metal pipe valve vaults for all three
,..
valves.
4. Move the air vent downstream on the penstock to fit in the valve vault around the
upper valve.
5. Install an 8 feet wide by 20 feet tall trashrack in front of the penstock intake. This
,.
trash rack will consist of a vertical corrugated metal pipe with the face cut at an angle.
^
6. Extend the three, 10 inch spillway pipes into the reservoir to provide overflow
!�
protection when the reservoir is frozen.
7. Install air vents for the three extended spillway pipes to prevent siphoning.
,.,
8. Relocate the water level pressure transducer in a stilling well (currently located within
^
the trashrack).
p+
Condition Assessment Report Page 15 July 29, 2011
^
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r
^
City of Akutan Town Creek Hydroelectric Project
n
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9. Repair or replace the main impoundment dam consistent with the approved Periodic
r
Safety Inspection.
An inspection of the main impoundment dam indicated that the dam experiences uncontrolled
seepage, the sheetpile cap requires replacement and the spillway which consists of a battery of
F
three pipes has no system to stop potential clogging with debris. Each of these issues is
F.
discussed in more detail in the following paragraphs.
4JA Intake Works
The existing penstock intake does not have a trashrack or screen to prevent debris from entering
the pipe and affecting the turbine valves. It is recommended that a trashrack be installed on the
intake to prevent debris from entering the penstock. The trashrack would be
r^
penstock
approximately 8 feet wide by 20 feet tall. When developing the trashrack design, consideration
for pulling flow from the middle to the top of the water column should be considered to prevent
r„
sediment entrainment into the penstock. This could be accomplished by placing a vertical pipe
riser over the penstock intake with a cutout section on the reservoir side where the trashrack
would be installed.
r
4.1.5 Reservoir
,r.
The bank on the east side of the reservoir has an exposed bank which appears to be contributing
sediment to the reservoir. Replanting or stabilization of this bank should be completed to
eliminate the sediment source. When the reservoir is lowered to complete the overall system
^
improvements, the accumulated sediment should be removed to return the full dead storage
volume to the reservoir capacity.
4.1.6 Upstream Slope
r
There are no improvements required for the upstream dam slope.
^
4.1.7 Crest
..
The damaged pile cap should be repaired and gravel added to the dam crest.
^
4.1.8 Downstream Slope
^
There are no improvements required for the downstream slope of the dam.
^
^.
4.1.9 Abutments/Toe
^
Based on the field inspection, it appears that 0.5 to 1.0 efs is leaking through the toe near the
i"
abutment areas; however no erosion is evident. The water is flowing through the riprap
�.,
protecting the abutments. The seepage water is clear. At a minimum, this condition calls for
monitoring of the seepage to ensue the amount does not radically change nor does it change
^
from clear to cloudy which would indicate internal erosion of the dam. Weirs located at places
r^
where the water collects downstream from the toe could be established to create a record of
Condition Assessment Report Page 16 July 29, 2011
T
^
r
^ City of Akutea Town Creek Hydmelect6e Project
^ seepage based on measurement taken when people inspect the dam. Seepage measurements
^ should also be held relative to the stage of the reservoir with higher stages expected to have
greater seepage.
^ The loss of up to lefs represents a significant loss of water that could be used in hydropower at
^ key times. In order to deal with this seepage issue, a corrective measure without replacing the
,., it= could be to install a soil/clay blanket along the upstream side of the dam. One problem with
this approach is the upstream slope of the dam is at 13:1 so this would represent a great deal of
r material and if the problem is associated with water coming underneath the sheet pile, seepage
r issues may not be addressed by this approach. For this reason this approach while commonly
1. used for many dams is not recommended here. Another approach would be to drive new
sheetpile deeper upstream from the existing pile. However, this approach may not work if there
r is irregular rock near the bottom interface between the dam bottom and native material. Finally,
r^- this degree of seepage in combination with other dam performance issues could be a justification
for replacing the dam with a new dam that has a deeper cutoff trench and more reliable core
material such as mixed in clay to greatly reduce or eliminate uncontrolled as well as controlled
seepage through drain pipes.
4.1.10 Spillway
In order to reduce the potential for debris and ice blockage of the existing spillway pipes, the
`.
existing pipes should be extended out into the reservoir. Placing the pipeline intakes at a lower
point in the reservoir would ensure the pipe inlets are submerged and protected from ice
r,
formation during cold conditions. Intake screens should be considered on each of the three pipes
^
to prevent debris from plugging the pipe inlets. Air vents should be added at the dam crest for
r-
each pipe to prevent water siphoning.
^
4.1.11 Drains
The drainage system appears to consist of a combination of drainage mat downstream from the
sheetpile and a collection system with a corrugated six-inch pipe and possibly a 10-inch HDPE
pipe. Flow was passing through the CMP pipe during the September 2010 visit. However, there
.-
was significant uncontrolled seepage estimated at 0.5 to 1.0 efs as well. This may be due to use
of a drainage mat (not currently accepted technology) rather than granular filter. Addressing
r,
seepage as discussed in section 4.1.9 may help alleviate some of the uncontrolled seepage
described and may also reduce seepage in the drain pipes as well.
^
4.1.12 Downstream Channel
^
The downstream channel is in good condition except where the overland flow has reentered the
channel, causing moderate erosion. The erosion damage should be repaired through placement
of rock material and/or re -vegetation of the channel surface.
r'
r Condition Assessment Report Page 17 July 29, 2011
r
^' City of Akutao Town Creek Hydroelectric Project
^ 4.1.13 Penstock
The condition of the buried portion of the existing penstock is unknown. A camera inspection is
recommended to confirm the structural integrity of the penstock. It is anticipated that the overall
^ pipeline is in good condition due to the use of HDPE pipe and protected nature of the pipeline
^ routing. The inoperable condition of the three valves is the primary reason for the poor rating.
Though the valves have been operated by the City, it is recommended that the three valves be
replaced in order to ensure reliable operation.
4.1.14 Outlet Works
r-. There are no improvements required for the outlet works.
4.1.15 Powerhouse / Turbine
Though the turbine, generator, and powerhouse building were considered to be in satisfactory
r condition, the existing Pelton Wheel turbine is over 20 years old and requires an overall
r' inspection and servicing by the manufacturer, Canyon Industries. A comprehensive inspection
should be completed for the entire turbine generator system to ensure all components am in
r" good, operable condition and the system is ready for continuous use.
n
4.1.16 Instrumentation
r- The existing electrical control system is unreliable and restricts the operation of the hydro facility
�., with the diesel generation system. To provide a more reliable system, it is recommended that the
electrical control system be replaced.
r+ The pressure transducer to measure water level in the main impoundment reservoir was non-
operational. A new water level sensor was installed on November 26, 2010 to the end of the
cable and reinstalled in the reservoir. Resistance measurements were recorded at the powerhouse
r but were very high/open resistance (4 Meg ohm) on the two wires attached to the probe. The
r- wire from the reservoir to the powerhouse was reported to have been accidently dug up at one
point. According to the measurements taken at the powerhouse, the wire may be damaged and
not able to send messages to the powerhouse. A new temporary control cable is being placed
above the ground surface to allow operation of the powerhouse during the spring runoff. The
cable will remain in place until the improvements to the Town Creek Dam are underway.
4.1.17 Documentation of Procedures
As revealed as part of the existing system assessment, the Operations Plan, Monitoring Plan, and
^ Emergency Action Plan will have to be completed. These documents will be required to obtain a
Certificate of Operation from the Alaska Dam Safety office.
r. 4.2 Cost Estimates
Concept Level cost estimates were prepared for each of the recommended improvements
r` outlined in the previous paragraphs.
�. Condition Assessment Repon Page 18 July 29. 2011
r
City ofAkutan Town Creek Hydroelectric Project
Table 4-1. Summary of Existing Town Creek System Improvements and Costs
Item
No.
Description
Recommended Improvement
Estimated
Cost
I
Access/Securiity
Construct access road, install locks on gate operators
$184,342
2
Diversion Dams
Repair sheetpile, excavate sediment, compact fill around
dam crests, install rashracks, Install sediment sluice pipes
$50,000
3
Main Impoundment
Dam
Conduct field seepage investigation to collect data, then
determine if repairs or replacement are recommended
$200,000
4
Intake Works
Install vertical inlet riser and trashmck
$66,920
5
Reservoir
Repair erosion area and remove sediment
$6,000
6
Upstream Sloe
No work anticipated
0
7
Crest
Repair damaged ed shee ile and place gravel on crest
$10,000
8
Downstream Sloe
No work anticipated
0
9
Abutments/Toe
Included in main impoundment dam
Included in
Item 3
10
Spillway
Extend spillway pipes into the reservoir, add vents, add
screens on the pipe inlets
$31,476
I I
Drains
Conduct field investigation to determine source of drainage,
then determine if repair or full replacement is required
Included in
Item 3
12
Downstream Channel
Repair the eroded channel bank
$2,000
13
Penstock
Replace three valves and conduct camera inspection of
enstock
$42 164
14
Outlet Works
No work required
0
15
Po werhouse/Turbine
Conduct turbine inspection
and repair
$27,000
16
Control System
Improvement
Install temporary cable for interim operation, then install
permanent cable with finals stem improvements
$75 000
17
Maintenance
Equipment and
Storage Building
Installed pm -manufactured building at the dam site to park
excavator and Maintenance Equipment
$107,000
18
Complete System
Documentation
Prepare Operations Plan, Monitoring Plan, and Emergency
Action Plan
$30,000
19
Engineering
Dam stability analysis
$10,000
Hydrologic analysis of Town Creek u1
$10,000
Seismic stud
$15,000
GeotecliZal investigation
$50,000
Inundation study
$10,000
Augmentation of the City of Altman water supply
$5 000
Final Plans and Specifications
$30 000
20
Permitting
$20,000
Subtotal
$981,902
Contingency 30%
$294,571
Total
$1,276,473
tr) munaarmn sway may nor oe reym uu m�e aucw um m,.,, �,.�,,.
(2) The geotechnical investigation assumes using the City of Akutan excavator to explore the dam toe end abutment to detem me
the source of seepage, confirm the dam as -constructed methods, and determine the sheetpile cutoff wall construction method.
Condition Assessment Report Page 19 July 29, 2011
City ofAkumn Toum Creek Hydroelectric Project
R't
r SECTION 5
FINDINGS, CONCLUSIONS, AND RECOMMENDATIONS
.�
5.0 Findings
^
Field Report Engineer's Estimate determined that system maintenance and
^
The Preliminary and
operations are the primary factors affecting performance and power production. Therefore, the
recommended actions and associated costs focused on returning the system to optimal operating
..
condition and instituting a formal operations, maintenance and safety program. This remains as
^
the principal finding of our work. However, with the completion of the PSI and review of dam
^
safety issues with the DNR Dam Safety Office, we have determined that a significant amount of
,-
additional investigation and analysis may be required before construction of needed repair and
upgrade can begin, most specifically, studies and actions necessary to obtain certificate(s) to
repair, modify or construct a dam.
r•
Section 5 presents the conclusions and recommendations that should assist the City and AEA
^
with determining a future course of action.
r"
5.1 Conclusions
r
A condition assessment was conducted on the existing Town Creek Hydroelectric project to
_
determine the required system improvements to return the hydroelectric project back to reliable
^
operation. The assessment included all features of the existing facility from the small diversion
^
dams to the main impoundment dam to the powerhouse. The majority of the system components
were found to be in fair to satisfactory condition, with the exception of the main impoundment
A'
dam. The dam had a number of deficiencies which could impact the overall dam safety
r-
including inadequate spillway design and seepage. Of these, the identified seepage is of primary
r
concern
Overall, little is known about the actual design and construction of the existing dam. The
observed seepage presents a challenge in identifying and remediating the source to ensure long
term data stability and maximize power production. Replacing the data has a significant capital
cost requirement which is not fully justi fled without completing additional field investigations.
For this reason, field explorations of the dam abutments and toe with the City owned excavator is
�-
recommended. Dye testing is also recommended. If the field investigations are not successful in
isolating the seepage source, then a final determination can be made on whether to repair or
replace the dam.
.-
5.2 Recommendations
The existing Town Creek Hydroelectric facility assessment revealed a number of improvements
that are required to return the existing system to reliable operation. It is recommended that these
.-
improvements as summarized in Table 5-1 be implemented. As a first step, a geotechnical
investigation is recommended, including field explorations and dye testing on the existing main
^
impoundment dam, to determine the seepage source. Depending on the results of this field
^
Condition Assessment Report Page 20 July 29.2011
^
^
City ofAkutan Town Creek Hydroelectric Pmiat
investigation, the decision on whether to repair the existing dam or replace it with a new dam
should be revisited to determine the most cost effective approach.
In addition to the capital improvements to the existing hydroelectric facilities, additional studies
and completion of the project documentation is recommended. These studies were identified
^ within the PSI and include the following:
• Dam stability analysis
• Hydrologic analysis of Town Creek
• Seismic study
• Geotechnical investigation
• Inundation study (may not be necessary in light of the small storage)
• Augmentation of the City of Akutan water supply
• Operations and Maintenance Plan
• Emergency Action Plan
As an interim measure, it is recommended that seepage monitoring be implemented at the dam.
The parameters which should be measured, observed, and recorded include:
1) Rate of flow of seepage
2) Is the rate changing with time?
3) Is the rate of flow changing with the reservoir's water surface elevation (stage)?
4) Clarity of seepage — for example is the seepage cloudy or clear?
Condition Assessment Report Page 21 July 29, 2011
r
City of Akutnn Town Creek Hydroelectric Pmjeet
r
n
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A
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^
APPENDIX A
^
PHOTOGRAPHS
^ Condition Assessment Roped July 29, 2011
^
City of Akuten Town Creek Hydroelectric &ajed
MAIN WOUNDMENT DAM
Photograph 1. Main Impoundment Dam Embankment
Photograph 2. Outlet Pipes
Condition Assessment Report
I
City ofAkulan Town Creek Hydroelectric Project
Photograph 3. Flow Through Pipe Outlets
Photograph 4. Seepage at Toe of Main Impoundment Dam
Condition Assessment Report July 29.2011
City of Akutan Town Creek Hydroelectric Project
Photograph 5. Sluice Pipe Outlet
Photograph 6. Air Vent and Valve Riser
Condition Assessment Reporl Joly 29. 2011
City of Akutm Town Creek Hydroelectric Project
Photograph 7. Impoundment Reservoir
Photograph 8. 12iprap on Embankment
Condition Assessment Repon
July 29, 2011
City of Akman Town Creek Hydroelectric Project
A
r—
Photograph 9. Impoundment Reservoir
Photograph 10. Sediment Source at Northeast Corner of Reservoir
Condition Assessment Report
July 29, 2011
City of Akutan Town Creek Hydroelectric Project
Photograph 11. Overflow Pipe Inlets
/hAVOK Allillx
F
Photograph 12. Cutoff Wall
Condition Assessment Repon July 29. 2011
City of Akuten Toam Cmek Hydroelectric Project
Photograph 13. Cutoff Wall Materials
Photograph 14. Impoundment Reservoir Level Sensor Location
Condition Assessment RepW
City of Akman Town Creek Hydroelectric Project
Photograph 15. Level Sensor Riser
Photograph 16. Level Sensor Configuration
Repon My 29,2011
City of Akutun Town Creek Hydroelectric Project
Photograph 17. Level Sensor Electrical Connector
Photograph 18. Vent Location for Level Sensor
Condition Assessment Repon July 29, 2011
City of Aku m Town Creek Hydroelechic Project
TOWN CREEK CHANNEL NEAR COMMUNITY SCHOOL
Photograph 19. Town Creek Channel Above School Building
Photograph 20. Bridge Crossing at Corner of School Building
Assessment Report
July 29. 2011
City of Akutsn Town Cmek Hydroelmoic Project
Photograph 21. Town Creek Channel Below School Building
Photograph 22. Main Boardwalk Bridge Across Channel
Condition Assessment Report
City of Akutsn Town Creek Hydroelectric Project
Photograph 23. Main Boardwalk Bridge Supports
Photograph 24. Town Creek Channel Above School Building
Condition Assessment Report July 29, 2011
City of Akuten Town Creek Hydroelectric Project
Photograph 25. Channel Beneath Bridge Crossing Near School Building
Condition Assessment Repon July 29, 2011
'�
��R"`� .-
,�.
,: ,,
�yy,/' �- �`r ,,ems ..
S"."'- � �-S4 f 4r. WM i1
,3 .� �":
�k. S r� '� ��fF
City of Akulan Town Creek Hydroelectric Project
Photograph 28. West Diversion Structure #2 —Reservoir
Photograph 29. West Diversion Structure #2 — Overflow Pipe
Condition Assessment Report
City of AkWen
Town Creek
Photograph 30. East Diversion Structure
Condition Assessment Report July 29, 2011
of Akuten
To. Creek
APPENDIX B
COST ESTIMATES
Condition Assessment Report July 29, 2011
Town Creek, Concept Level Cost, Condition Assessment
July 29, 2011
COSTSUMMARY
Dam Repairs and Improvements
$
408,560.00
Access Road
$
184,342.00
Maintenance Equipment and Storage Building
$
107,000.00
Turbine Inspection and Maintenance
$
27,000.00
Control System Improvement
$
75,000.00
Complete System Documentation
$
30,000.00
Engineering
$
130,000.00
Permitting
$
20,000.00
Contingency at 30 %
$
294,571.00
Total
$
1,276,473.00
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Town Creek Hydro Condition Assessment Concept Level 07/29/11
Powerhouse / Turbine Inspection and Minor Repairs
Turbine Manufacturer Inspection
$22,000
Small Parts Allowance
$5,000
Subtotal
$27,000
Contingency
$o
Total
$27,000
Town Creek Condition Assessment Concept Level 07129/11
Control System Improvements
Im rovements to the ExistingSystems
$
40,000
Re lace Radio with Fiber
$
5,000
jUpgrade HMI/Server
$
30,000
Totall
$
75,000
Complete System Documentation
Com fete System Documentation
$
30,000
Totall
$
30,000
Engineering
Dam Stability Analysis
$
10,000
Hydrologic Analysis of Town Creek ('1
$
10,000
Seismic Stuldy
$
15,000
Geotechnical investigation
$
50,000
Inundation Study
$
10,000
Augmentation of the City of Akutan Water Supply
$
5,000
Final Plans and Specifications
$
30,000
Total
$
130,000
t,/ munnanon store mayn0,. rtgwred due to the ..It scosage scut of,hc dam reservoir.
(2) The geotechniwt investigation assumes using the City of Akutan excavatorroa;plore the dem toe
and abutment o determine the source ofsac age, confirm the dam as<onsrrucred methods, and determine
the sheetpile cutoff wall construction method.
Permitting
Pennittin
$ 20,000
Total
$ 20,000
City of Akman Town Creek Hydroelectric Project
APPENDIX C
AS -CONSTRUCTED DRAWINGS
July 29, 2011
UNALASKA
TOWN CREEK HYDROELECTRIC PROJECT
CITY OF AKUTAN, ALASKA
EXISTING PROJECT DRAWINGS
LOCATION MAP
NTS
IORAGE _.
VICINITY MAP
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LOCATION MAP, VICINITY MAP,
AND DRAWING INDEX
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ABBREVIATIONS
SHEET SYMBOLS
ffi
AND
EW
EACH WAY N
NORTH, NEUTRAL
SYM
SYMBOL
1/0
OPEN -CLOSE
E%C
EXCAVATION N/A
NOT APPLICABLE
SYMM SIMMETRICAL
ICI
END
EXTERIOR, EXTERNAL, EXTENSION NO
NORMALLY CLOSED
SYS
SYSTEM
ARROW INDICATES�
AMP
NUMBER
DIRECTION OF
ABBREV
ABBREVIATION
FAB
FABRICATE NO
NORMALLY OPEN
T&S
TOP AND BOTTOM
PLAN NORTH
AC
ASPEREHALT
ASPHALT CONCRETE
FB
W.
FLAT BAR NO
NUMBER
1MM
TEMPORARY BENCHMARK
AD
CONCRETE INTERNATIONAL
AMERICANMEMORIAL
FOR
FOUNDATION NOS
NOMINAL
TEA
TOTAL DYNAMIC HEAD
A➢OL
AMERICAN
EF
FlNISHED RODE NPS
NOMINAL PRE SIZE
TEMP
TEMPORARY
W
NSC
PM INSTITUTE OF STEEL
FG
FINISHED GRADE NPSH
NET POSITIVE SUCTION HEAD
M
TANK
PLAN
CONSTRUCTION
ONST
FIG
FIGURE NRS
NATIONAL PIPE THREAD
TMTR
THERMOMETER
ALG
ALIGNMENT
FLA
FLOOR FLANGED NRS
NON -RISING STEM
OPOF
TO OPNG TOP OF OPENING
SCALE: 1/2"= 1'-0'
ALT
ALARM
FLR
FLOOR NIS
NOT 1D SCALE
NB
TOP OF BANK
ALT
ALTERNATE
FOC
FACE OF CONCRETE
TOO
TOP OF CONCRETE
ALUM
ANGLE
FITµ
FACE OF WALL 0&M
OPERATIONS AND MAINTENANCE
TOGGLE TOP OF CMU
AND
ANGLE
FPS
FEET PER SECOND OC
ON CENTER
TOGGLE TOP OF
SECTION IDENTIFICATION
ARCH
APPROXIMATE
PET
FEMALE PIPE THREAD OR
OUTSIDE
TOE
DUCT
TOP OF DUCT
ARCH
ARCHITECTURE E
FT
FOOT/FEET OF
FACE
OUTSIDE FACE
NF
NP OF FOOTING
AS
AIR SUPPLY
FIG
FRTING OF
OVERFLOW
TOG
TOM
TOP OF GRATING
TOLERANCE
(1) SECTION CUT ON ORAWNG Cf 02:
ASD
ASSY
ALLOWABLE STRESS DESIGN
ASSEMBLY
Fµ
MILE) W
FIELD WELD on
OPT
OPENING
OPTIONAL
TOM
TOP OF MASONRY
SECTION
AUTO
AMC
AUTOMATIC
AUXILIARY
G
GA
CAS ORIC
GAGE (GAUGE THICKNESS) OUT
O%GINAL
OVRH
TOP TOP GR PUTE/PIPE
TWO TOPOGRAPHIC
LETTER
AMC
AVERAGE
G4
GAGE, CADGE OWHG
OVERHANG
TOW
SLUM
TOP OF SUB/STEEL
A
CALL
GALLON OWSJ
OPEN WEBBED STEEL JOISTS
NW
TOP OF WALL
C102
B/W
BACK OF WP11
GE
GALVANIZED OZ
OUNCE
TP
E
TELEPHONE MILE
MR
&ISSUER
OEM
GALLONS PER MINUTE
TYP
TYPICAL
BE
BINE
OR
GRADE P
PUMP
DRAWING WHERE
IDG
WILD
BUILDING
GALGRAVEL
PA
ACTUATOR. PNEUMATIC
DEC
UNIFORM BUILDING CODE
SECTION IS DRANK
HIM
BENCHMARK, BEAM
PAR
PARALLEL
UDC
UNIFORM FIRE CODE
BOP
BOTTOM BE FOOLING
HERE
HIGH DENSITY POLYETHYLENE PC
POINT OF CUM, PRECAST
UG
ND
UNDERGROUND
(2) ON DRAWING C10.1 THIS SECTION IS IDENTIFIED A5:
BOP
BOTTOM/BEGINNING OF PIPE
HEX
HEXAGONAL PCC
CONCRE
POUNDS➢ CEMENT CONCRETE
HIGH
UHL1W ULTRA HIGH MOLECULAR
BOO
BOTTOM
HGL
HYDRAULIC GRADE LINE ME
POUNDS PER CUBIC FOOT
WEIGHT
SECTION
PRO
BEARING
HE
MOT
HORSEPOWER MOT
PERCENT
JET
ULTIMATE
BRCP
BEARING PULE
HWE
HOLLOW STRUCTURAL SHAPE PEN
PEN
PEDESTAL
PENETRATION
UNIT
UPC
UNLESS NOTED OTHERWISE
UNIFORM PLUMBING CODE
LETTER
SECTION A
BS
BTU
BIT SIDES
BRRUTISH THERMAL UNIT
HTR
NVAC
HEATER
HEATING. VENRUTIDN, & AR PERM
PERFORATED
UPS
POWER
SCALE: I/2"= 1'-0" C103
CONDITIONING PERM
PERMANENT
SUPPLY
SUPPLY
C
CONDOR
HWL
HIGH WATER LEVEL PERP
PERPENDICULAR
UTIL
MLIIY
CA
COMPRESSED AIR
HYD
HYDRANT PH
PHASE
DRAWING WHERE
CAR
COMPRESSED SNSSYSTEMHZ
HERTZ (CYCLES PER SECOND) PI
POINT OF INTERSECTION
V
VALVE, VAULT, VENT, VOLT(S)
DETAIL OCCURS'
CAW
DAM
CJ
CONTINUOUS ACTING AIR VALVE
PL
PUOE. PROPERTY LINE
Wp
VOLT AMPERE
CCW
COUNTER CLOCKWISE
I&C
INSTRUMENTATION PND CONTROL PLC
PROGCONTROLLER £ LOGIC
MAC
VACUUM, VOLTS ALTERNATING
OF
CUBIC FEET (FOOT)
IBC
BUILDING CODE
INSIDE
CONTROLLER
CURRENT
CFO
CUBIC FEET PER SECOND
10
INSIDE (OR INTERNAL) DIAMETER PH
(OR
P
VAR
VARIES. VARMBLE
DETAIL IDENTIFICATION
CH0
CHORD
IE
INVERT LLEVATION ME
PANEL
VC
VORTICAL CURVE
CHEMICAL
P
INSIDE FACE PREFAB
PREFABRICATED
MCC
VOLTS DIRECT CURRENT
DIP
DIP
CASs IN PULE
INCL
INCLUDE INCLUDING PRELIM
PRELIMINARY
E
VEL
VELOCITY
CJ
CONSTRUCTION
I
INSIRUMENTAIION PREP
PREPARE
VERY
VERDCdL
(1) DETAIL CALL -OUT ON DRAWING DETAIL
CL
ASS,JOINT
CENIERUNE, C V55, CLOSE
IRV
NV
IMIERi FREE
PRESSURE
VFD
VARVBLE FREQUENCY DUNE
NUMBER
CW
CONTROL JOINT
IRO
IRRIGATION PRV
VALVE. PRESSURE RELIEF OR
VOL
VOLUME
I
CUP
CLEAR
ISO
ISOMETRIC
POUNCING
V
VERTICAL POINT OF CURVATURECMP
CI D2
CORRUGATED SETAE PIPE
ESE
POUNDS PER SQUARE FOOT
VIN %
VERTICAL POINT OF INTERSECTION
_____
CNU
CONCRETE MASONRY UNIT
J8
JUNCTION BOX (J-BOX) PSI
POUNDS PER SQUARE INCH
VRT
OF TANGENCY
VERTICAL POINTSPEED
CLEAN L
JOT
JUNCTION PWIA
POUNDS PER SQUARE INCH
V50
VPRVBLE SPEED DRIVE
I I DRAWING WHERE
CO
GO
CLEAN OUT. CONCRETE WANING
JE
JOINT FILLER
ETAILI
( DETAIL I$ SHOWN
COL
COLUMN
Ji
JOINT PSIC
POUNDS PER SQUARE INCH GAUGE
POUNDS
µ
'WITH, WIRE. WASTE
I I
CONN
CONCRETE
Pi
POINT, POINT TANGENCY
µ/
WITH
CORN
CONNECTION
NIP
KIP (f 0OU BOUNDS) PVC
LO
PAVEMENT CHLORIDE
W/O
WITHOUT
----��
CONSTRUCTION
NO
KNOCK OUT PVAIi
PAVEMEM
WED
WELDED
(2) ON DRAWING C103 THIS SECTION IS IDENTIFIED AS:
cow
CONY
CONTINUED
KIT
KILOVOLTS
WS
WATER SURFACE, WATER SUPPLY
CONTID
CONTINUED
KW
0
KILOWATTS (REAL BOWER)
RATE OF FLOW
WT
WRIGHT, WATERIIGHi
DETAIL
COORDINATE
KWH
Ott
KILOWATT HOUR
OUAN111Y
ME
WELDED WIRE FABRIC
NUMBER
CP
OR
CHLORAL PONT
DETAIL 1
CHLORINATED POLYVINYL CHLORIDE
R
RADIUS
WEN TRANSFORMER
GENC
CSK
COUNTERSINK
LB
POUND RW
RECEPTICCIE
SEC
%SEC
CROSS SECTION
SCALE: I/2"= 1'-0" C101
CTR
CENTER
RCP
FOOT
PIPE. REINFORCED CONCRETE
LTHL
CONTROL
LL
REINS
LIVE LOAD
REINFORCE/REINFORCED
YD
YARD
DRAWING WHERE
CU
CUBIC
LEE!
LONG LEG HORIZONTAL REM
READ
REMOVE
REQUIRED
DETAIL OCCURS'
CULV
CULVERT
OEM
LONG LEG VERTICAL
REV
RETAINING
CV
VALVE, CONTROL
LONG
LONGITUDINAL
REV
REV610N
*NOTE: IF PLAN AND SECTION (OR DETAIL CALL -OUT AND
CW
CY
CLOCKWISE
CUBIC YARD
LID
ROW
RIGHT OF WAY
DETAIL) ARE SHOWN ON SAME ORAWNG. DRAWING NUMBER
MLIEO RPM
REVOLUTIONS PER MINUTE
IS REPLACED BY A LINE.
D
DRAN
LTG
LIGHTING
IRS
RISING STEM
DBE
DOUBLE
LV
LWL
LOUVER
LOW WATER LEVEL RT
RIGHT
DEG
DEG F
DEGREE
DEGREE FAHRENHET
MA
MILLIAMPERES S
SOUTH
DEMO
DEMOUTION
MAINE
MAINTENANCE SARI
SANITARY
CIA
DIAMETER
MAN
MANUAL SON
SCHEDULE
DIAG
DIAGONAL, DIAGRAM
MASONRY SCHHM
SCHEMATIC
STANDARD DETAIL IDENTIFICATION
GENERAL NOTESNOTES:
DIM
DIMENSION
MAY
MAXIMUMMUM SO
DEAN NORM
DIV DIVISION MECH MECHANICAL SEC SECONDARY.SECONDS
DIE
DEADSECTION DEAD LOAD
MCC
MOTOR CONTROL CENTER
(1) DETAIL CALL -OUT ON PLAN OR SECTION:
1. SCOPE OF WORK: THESE DRAWINGS WERE DEVELOPED
OUP
DUPLICATE
WF
SQUARE FOOT/FEET
BASED ON DATA AND INFORMATION COLLECTED DURING A
OWG(S)
CRAWMG(5)
RED
MFR
MEDIUM
MANUFACTURER ENT
SHEET
SLOTTEDDETAIL
STANDARD
TOWN CREEK HYDROELECTRIC PROJECT CONDUCTED 0&VI'E
FIELD INVESTIGATION AMID ENGINEERING SURVEY OF THEclb=o�"
/gypSLID
EAST, ELECTRICAL (DWG DISCIPLINE)
EACH
MII
GIN
MILEWLL SN
MINIMUM SSPA OG
SNOW LOAD
SUB ON GRADE
M101 NUMBER
OCTOBER 23 & 24. 2009 AND SEPTEMBER 8 & 9.4
2010.
• ' • sE
EACH FACE
MIWC
MISCELLANEOUS
SWING
THESE•
2. THESE ABBREVIATIONS APPLY TO 1HE ENTIRE SET OF••EGL
ENERGY GRADE LINE
MJ
MECHWICAL JOIM SPEC
CONTRACT DRAWINGS
EJ
EXPMJ$IDN JOINT
MOD
SO
MODIFY SS
SWARE
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IEL
ENGR
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EMBEDDED
EMBEDDE
MON
MPE
MST
MONUMENT STA
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MEAN SEA IEMFL STD
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3. JSTING OF ABBREVIATIONS DOES NOT IMPLY ALL
PBBREVMTIONW ARE USED IN THE CONTRACT DRAWINGS..•
••EE
{ a'A /EKED
END OP PIPE
mV
MILLPNLTS STIR
STL
STIRRUPSTANDARD
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4. ABBREVIATIONS SHOWN ON THIS SHEET INCLUDE VARIATIONS
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•
EQUIPMENT
HOPLOG
DETAIL
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•STG
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SIDE EOUPL SPACE
STAR
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NUMBER6
DETAIL
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ASW
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PUN
5. SCREENING OR SHADING OF
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CE12523., AwPREVENWN
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BOISE, ID 83702 x: zpB.xz.azlB
CITY OF AKUTAN
DESIGNED D.AXNESS
DRAWN R. GUERRERO
CHECKED M. MCMILLEN
ISSUED DATE 5/11 /11
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City of Akulm Town Creek Hydroelectric Psojuct
APPENDIX D
FIELD TRIP REPORT
Condition Assessment Report
TOWN CREEK HYDROELECTRIC PROJECT
FIELD TRIP REPORT
_
d �
49
EES CONSULTING, INC.
MCMILLEN, I.I.C.
OCTOBER 2009
Town Creek Hydro — Field Report
Introduction
Electric Power Systems contracted with EIS Consulting to provide a field review and recommendations
for repairs/upgrades to the City of Akutan, Alaska Town Creek Hydroelectric Project. The EES Consulting
(EES) engineering team includes McMillen LLC (MCM) engineers.
Mobilization
On October 25, 2009, Don Jarrett (EES) and Dan Axness (MCM) joined Robert Kirkman (RCM) in Akutan
to perform the field work and develop a preliminary report with repair/improvement recommendations
and cost estimates. This team had to spend two nights in Unalaska due to weather delay prior to getting
a flight to Akutan.
While in Akutan the team hiked into the Town Creek watershed on October 24, 2009 and saw the main
impoundment dam and diversion dams. The upper part of the watershed had up to 18 inches of snow so
it was not possible to completely assess the condition of all aspects of the dams. On October 25, 2009
we had Demetri take us across the bay so we could hike up into the Loud Creek watershed. Again there
was snow cover on the upper part of the watershed, but we were able see the locations of previously
identified dam sites and the powerhouse location.
Document/Data Review
We reviewed the following information relative to the Town Creek Project.
• Electric Power Systems, City of Akutan Hydro Inspection Report & Upgrade Cost Estimates, May
2003
• Grant Application of Akutan Hydroelectric System Repair, City of Akutan, Renewable Energy
Fund Grant Application, AEA-09-004, September 3, 2008
• Alaska Power Systems, ASTF Grant Agreement 924-277, Unitized Village Scale Hydro -diesel
Generation System, April 1994
• Akutan Hydropower Feasibility Study, HDR/Ott Water Engineers and Dryen & LaRue, 1989
• Akutan Hydropower, Preliminary Design Report, Ott Water Engineers, 1980
• Egor Eispov, LCMF Inc., Alaska Energy Authority, Akutan Rural Power System Upgrade, 2007
Background Information
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The City of Akutan entered into an agreement with a developer for the construction and operation of
the Town Creek Project. The developer, Alaska Power Systems (APS), packaged the powerhouse
equipment and performed construction of the project at Akutan in 1990. Three small diversion dams
were constructed to divert water to amain impoundment dam in the watershed above Akutan. The
small diversion dams used 6 inch PE pipe to run water from the small drainages to the main dam. From
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the main dam at elevation 800 feet above MSL a 10 inch PE pipe (penstock) was installed to bring water
to the powerhouse. The powerhouse located at 26 feet above MSL, had a unique hydro turbine-
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generator with a drive train that would allow a small diesel to connect to the turbine -generator through
a clutch.
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Civil Construction Information
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There is very limited documentation of the construction of the main dam, diversion dams and penstock
in the above documents. The ASTF Grant Agreement has good information on the powerhouse
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equipment (which does not reflect the current equipment arrangement). This documentation includes
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dam design information performed by Shannon & Wilson, but is more schematic in nature with respect
to the dams and does not show the locations of the intake screens, penstock and valves, etc.
Powerhouse Construction Information
There is good information on the powerhouse and generating equipment which was installed by APS.
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Information from the Electric Power Systems report indicates that significant issues have existed with
the diesel -hydro system control. The hydro turbine generator has a rating of 160 kW; however, it is
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connected to a load bank which may consume 50 kW or more forthe purpose of providing frequency
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regulation. The original connected diesel had a rating of 150 kW.
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Historical Energy Production Information
Filings and other data for the Alaska Energy Authority power cost equalization (PCE) program were
obtained from 1999 to 2009. Earlier studies for the City of Akutan include energy production in the late
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1980's. Power plant log sheets were also reviewed. This review indicates that there has been very
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limited hydro operation the last 10 years. Figure 1 presents monthly generation for both diesel and
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hydro. As can be seen from the figure annual energy production has been increasing over the last 10
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years. Average annual production over the ten year period was 538,000 kWh. Production in FY2009 was
566,000 kWh. In 1989 the Ciq/s energy production was 305,000 kWh so energy consumption has nearly
doubled in the last twenty years.
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Streomflow Information
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While APS apparently did streamflow measurements in the tributaries which come out of the watershed
there is little documentation of the studies. According to APS the hydro project would be able to
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generate 2,000,000 kWh annually. Based on studies done on North Creek and Loud Creek hydroelectric
production from a watershed of this size would be expected to be much less. For example, Loud Creek
has a drainage area estimated at 1.1 square miles with 10.8 CFS average discharge and Ott Engineers
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estimated 1,820,000 kWh annually. The Town Creek drainage intercepted by the dams was estimated by
EPS at 0.63 square miles, correcting for head production might be expected to be on the order of
1,700,000 kWh. Unfortunately no further hydrology studies have been performed to correlate the small
amount of streamFlows to a longer record to obtain a better estimate of average annual production.
Given the variability of monthly average flows energy production from Town Creek will be unlikely to be
able to supply all needs of the City.
Figure 1 Town Creek Diesel -Hydro Generation
1oom Town Creek Generation 1999 - 2009
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Interviews
We meet with Mayor Joe Bereskin and Demetri Tcheripanoff to better understand some of the project
history and problems. As we had read the original Town Creek project was conceived by Alaska Power
Systems (APS). Apparently APS went bankrupt and the City was notable to obtain any project
documentation aside from that contained in the final report for ASTF grant and some O&M manuals
F, which were provided by APS. According to the Mayor APSgear was "home-made" and not very reliable.
We asked about issues associated with the main impound dam and the diversion dams. The City has
r^ experienced problems with the intakes in the diversion dams (which feed water to the main dam). These
small diversion dams have become clogged with sediment and there is not any way to easily clean these
'- out. There are screens of some type which become clogged with organic debris. According to City staff
the main dam has similar problems.
r. According to City staff the hydro turbine runs well but is not presently being used because of the failure
of the main impound dam level sensor. The Mayor noted that the control system seems overly complex
and is difficult for them to troubleshoot and problems. The recent improvements by EPS was helpful as
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new components are off the shelf as opposed to custom built equipment as was originally supplied by
APS. The Mayor noted the difficulty for the City to properly operate a hydro project with local residents.
We asked about the construction of the main dam and diversion dams. The City staff was not very
r- knowledgeable about the construction. They did not that the contractor had brought in a dozer and
r backhoe for construction and had been able to get the equipment up to the upper watershed. City staff
noted that the intake screen on the dams clog with weeds and it is difficult to clean them as they are
�.-. underwater.
We asked about the City water supply system. The City water supply system diverts water into a
r" separate system and runs directly to the City water treatment plant. There is no interconnection
between the Town Creek hydra and the City water supply system.
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We asked about the status of the Town Creek Hydro Project and the Alaska Department of Dam Safety.
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The Mayor noted that a dam safety person had been to the site and concluded that the main dam is
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subject to regulation due to Its height.
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We asked about construction of an access road to facilitate operation and maintenance of the dams.
The Mayor noted that the soils are very erodible and the residents would not want to see an ugly road
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from below.
We asked about the second diesel generator power plant which the City maintains as a backup to the
diesel -hydro system. The Mayor stated that there is no reason to install any monitoring of this facility or
interconnect it in any way to the diesel -hydro plant.
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The regular hydro operator was out of town so we were not able to interview that person. We asked for
his contact information.
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Site review
Figures and photographs of the watershed, dams and powerhouse are Included in the Appendix. Figure
1 illustrates the Town Creek site showing the main impoundment dam and diversion dams located in the
upper watershed. Figure 2 shows the penstock route and powerhouse location. Figure 3 illustrates the
main impoundment design. Figure 4 illustrates the powerhouse as originally supplied by APS.
Dams
The team hiked into the upper water shed along the penstock route and visited the main impoundment
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dam and the three diversion dams (see photographs in the Appendix). The upper watershed has up to
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18-inches of snow so inspection was difficult. Due to snow and ice on the ponds we were not able to see
much more than the dams and the spillways.
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i-. It was noted that the spillways are pipes on the crest of the dam and there is concern about the
potential for overtopping if the pipes get frozen due the snow/ice. Should there be a rain on snow event
while these pipes are obstructed the dams would be overtopped and likely fail.
.� At the main dam we were unable to operate the penstock shutoff valve or the sluice valve; they are
apparently jammed. We could not see the screen on the penstock intake. The screen may be damaged
or have large openings as evidenced by the amount of debris found in the needle (spear) valves.
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r- The diversion dams all appear to be silted in. Diversion dam #3 is damaged and sheet piling has been
washed out or frost jacked. In addition, the wooden cap protecting the upper end of the vinyl sheet
piling has deteriorated.
'- Powerhouse
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The hydro -diesel powerhouse was visually inspected (see photographs in the Appendix). The original
powerhouse configuration had a diesel engine directly connected to the hydro turbine through a clutch
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arrangement. It is not known when this arrangement was changed; however, the arrangement now has
a separate diesel gen-set.
The hydro turbine is a two -jet impulse machine manufactured by Canyon Hydro in Deming, Washington.
This a compact horizontal unit which is rated for 150 kW with a net head of 685 feet and 3.5 CFS
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discharge. The deflectors are hydraulically operated with a counter weight for emergency operation.
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The needles are also hydraulically operated and have limit switches for open/closed position indication.
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A visual inspection was made of the turbine runner was made and the runner appears to be in excellent
condition. The general condition of the turbine appears good. The turbine shutoff valve (8 inch 300#
gate valve) is outside of the powerhouse and is hand operated. The condition of this valve is not known.
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For typical hydro projects this shutoff valve would be located indoors and be protected from the
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elements.
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The hydro turbine is connected through a flexible coupling to an 1800 RPM synchronous generator rated
at 140 kW, 0.8 power factor which produces power at 480 V.
The hydro turbine -generator uses a Thomson & Howe control system. This system utilizes a load bank
for regulation of frequency, allowing rapid response to changes in system load. Impulse turbines do not
regulate frequency well (due to slow needle closure timing( so generally either deflector control or a
variable load bank must be used. Thomson & Howe also supplied small hydraulic power units for the
needles and deflectors.
While we were there the Mayor attempted to put the hydro unit online. The unit began to spin, came up
to synchronous speed, closed in and loaded up to 30 kW. Shortly thereafter the unit tripped off.
According to the HMI there was no alarm which indicated why the unit tripped off line. It was not clear
what the issue was with putting the hydro unit online. The HMI indicated a penstock pressure of 331 psi
when the unit was off-line. As noted previously the main dam level sensor is not functioning so there is
no way to monitor the amount of water in the main dam.
The HMI system for control and monitoring of the diesel -hydro powerhouse was inspected. The Mayor
demonstrated the HMI system which uses a desktop PC in the City Hall. This is the new HMI system
which was developed and installed by EPS. The diesel gen-set was producing 80 kW at 490 V on October
26, 2009 at 17:00.
The diesel in the powerhouse is a relatively new John Deere with a generator rating of 150 kW. The
controls for the diesel are using the Thomson & Howe original equipment which has been modified by
EPS. While there we observed that the diesel was operating satisfactorily and system frequency looked
stable.
Penstock Headlosses
The frictional losses in the penstock have been estimated based on the following:
^., Main impound dam water surface elevation 800 FT above MSL
Turbine runner elevation 26 FT above MSL
Penstock length 3000 FT
Penstock diameter 10 IN
Penstock material Polyethylene (PE) pipe
Turbine maximum discharge 3.5 CFS
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There is no documentation about the penstock that we were able obtain, other than statements in the
data reviewed that 10 inch PE pipe was used. We were able to confirm the 10 inch diameter PE pipe at
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the powerhouse just upstream of the outdoor 8 inch isolation valve. Standard IPS PE pipe comes in
different pressure ratings. The gross static head Is 776 feet which is 335 psi. A PE pipe with a diameter
to wall thickness ratio of 7.3 has a pressure rating of 320 psi, so this is likely what was used. They may
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have used a combination of lighter wall thickness pipe further up the penstock. None -the -less based on
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the assumptions above the estimated headloss due to friction at full load is 64 feet. Thus the net head at
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the turbine would be 710 feet of head. This is consistent with information obtained from Canyon Hydro
(the turbine manufacturer) that the turbine was designed for 685 feet net head and 3.5 CFS.
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Recommendations
Dam repairs/modifications
Modifications and repairs to the dams in the upper watershed are needed for maximizing the capture of
water in the watershed.
The modifications recommended for the main impoundment include:
1. Replace all three valves. (2) 10" valves at the dam and (1) 8" valve at the powerhouse
near the harbor
2. Provide insulated valve vaults for all three valves (6' dia. Cmp)
3. Move the air vent downstream to fit the valve vault around the upper valve
4. Install an 8-ft wide by 20-ft tall trash rack that consists of a vertical 8' dia. CMP with the
face cutoff at an angle
5. Extend the 3-12" over flow pipes 80-fit into the pool to provide overflow protection
when the pool is frozen
6. Provide air vents for the three overflow pipes to prevent siphoning
7. Re locate level sensor into trash rack in a stilling well.
Modifications recommended for the smaller impondments include:
8. Excavate small ponds (— 50 cy each)
9. Provide small trash racks for the three small ponds (8-ft x 3-ft horizontal trash racks)
10. Install sediment sluice pipes through the vinyl sheet piling.\ on the three small dams.
Backfill and replace slope protection.
Upper water shed access road
1. To properly operate the dams in the upper watershed reasonable access must
be provided so the staff can safely travel to these locations and inspect
and maintain the dams. An access road with reasonable grades would allow
AN access in the summer and snowmobile access in the winter.
2. Provide an access trail for 4-wheeler/gator/snowmobile
a. Use some gravel from the harbor
b. Use cellular confinement material (grid) or geotextile to forma base and sides
where the trail cuts through ridges
c. Reestablish vegetation to maintain low visibility of trail
Control system replacement
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r" Given the difficulty of City operations staff to get unit to properly parallel with the diesel it is
recommended that the control system be replaced. Electric Power System will address this
recommendation and the associated estimated cost in their report.
Turbine inspection
It is recommended that a service technician from Canyon be brought to site to perform a full Inspection
of the unit. While the unit has not had a lot of hours of operation it is nearly 20 years old and inspection
and servicing is recommended by a factory technician.
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Cost Estimates
Dom repairs/modifications
The three small impoundments will be excavated to remove sediment, have fill compacted around the
scoured areas at the dam crest, be fitted with 3-ft by 8-ft trash racks, and have the pressure treated
wood sheet pile protection replaced.
The main impoundment will have the overflow pipes extended into the reservoir to provide ice free
overflow protection. In addition, the main penstock will have the outlet valve, the sluice valve and the
powerhouse valve replaced. All of these valves will be protected in 5 to 6-ft diameter corrugated metal
pipe valve vaultsThe cost for these repairs is estimated at approximately $297,000, which includes
surveying, design, permitting, construction management, materials, and labor.
Upper water shed access road
The access to the impoundments will be improved with a new ATV road. The low -visibility road will use
a geotextile base in places to stabilize the surface and reduce erosion. Finally, vegetation will be
established along the road and construction areas. Estimated cost for the road construction is
approximately $266,000, which includes surveying, design, permitting, construction management,
materials, and labor.
Control system replacement
To be estimated by Electric Power Systems.
Turbine inspection
Cost for a Canyon factory technician to travel to Akutan and inspect the turbine is estimated at $11,000.
An allowance for repairs (bearings and packings, etc.) of $5,000 is recommended.
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Figure 1—Town Creek Site Plan
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Figure 2 - Penstock Route and Powerhouse Location
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Photographs
Diversion Dam #1
iR in .
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Main Impoundment Dam
Main Dam Spillway
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Main Dam (from downstream)
Diversion Dam N2
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Diversion Dam #3
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_ err
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Turbine hydraulics and load bank
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Turbine control panel
Turbine load bank controls
City ofAkutnn Town Creek Hydroelectric Pmject
Assessment
APPENDIX E
DAM SAFETY REPORT AND PERIODIC SAFETY
INSPECTION
July
r
r
r
r^
r
r
^
r
r
^ Periodic Safety Inspection
r
^ Akutan Town Creek Hydro Dam
r
(AKOO264)
June 1, 2011
r
near Akutan, Alaska
r-
�, 540 8'33.79"North Latitude, 165° 4626.33" West Longitude
r—
Prepared For:
r
City of Akutan
P.O. Box 109
Akutan, AK 99553
Prepared By:
McMillen, LLC
1401 Shoreline Drive
Suite 100
Boise, to 83702
City ofAkutan Town Creek Hydroelectric Pro ect
Periodic Safety Inspection
Akutan Town Creek Hydra Dam
(AK00264)
June 1, 201t
New Akutan, Alaska
54"8'33.79"North Lwilude, 165"46'26.33"Wen Langifude
Prepared For:
City of Akwan
P.O. Box 109
Akutan, AK 99553
Inspected and Prepared by: /mil �,Jkkj4 ^^ Date L Z f
Morton D. McMillen, P.E., Chief Engineer
McMillen, LLC,�
Reviewed and Approved by: Date 720//
Charles F. Cobb, P.E.
Dam Safety Engineer
Alaska Department of Natural Resources
OFCO- ,�I •' 9�
f: 4Wh
P, •,MORTON D. MCMILLEN R
O•
No. CE72523,•�
Draft Periodic Safery Inspection Page i June I, 2011
�
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TABLE OF CONTENTS
�
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PROJECT DATA SHEET ...........................................................................................................................
iv
Section IIntroduction ............................... ...~..�.�~~~~.�...,..........--.~.}
r-
1.0 Location and Ownership ....................................................................................................................
I
�~
Ll Scope ................................. .~.~~~-~.~~~^^^.~~~~^--~~~~~~~~^'~~~~~
1.2 Pu�*�})�oo6o�nu....~~�'...~....-,.~.�.^-~~�.
' � --^`~^~^--^~^~~-~~
|
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� 0biuImpoundment Dam and Reservoir ........-`..~...-
.............. ................ 2
112 Diversion Dams ..--....-~...--..~~~-.~~~.~�~~~-,�.~.~-~~.--~
|2���u��oc�
�� ~~~..~~~~................. -~.~..~.............. -~.......
^^-~...~~.~~^',.... 3
l24Low Level Conduit '~^~^~--~^~^--~.^^^^^~~^^'`~~^~-..~...~......3
y~
l] Hazard Potential Classification Review ......................................................
--,~~.~~~~.~.~3
Section History ~.........~~~~^^.,~~-~.^~--^^^~~^~~�^`~~~^�^~~~`~�^
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10
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........... -....... ....................... 7
12 DescriptionofEnvironmental Conditions During the Inspection ........
.-........................................ ?
3.3 Highlights o/Visual Inspection ........................................ ~~~.-...--,~...~~~.�~~~.
'-
Sec�nu48pe/u6oum�d��uiuten000cReview �.�,�...�.�.����������.��...������.9
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9
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4.2 Operation and Maintenance Plan ^�`9
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��~~^-�^ 12
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-�^^`~~^^' 12
6J.3 Upo�emmS|opo '~--~~^~~~`^^^~-~~^-~~^^�~~-~~^...............................11
63/| Crest ��-~~--~~--^~-~~'~~^--`^^^~~^`~~^^�^^^
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��~~~^'~^^`~~ 12
k3j Dono�u�oouSlope -~~`~~~^`~~~^^^^`~~`-~~~`.^^^~~~.
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14
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Fenonic safety inspection Page"
Jom'|, 2011
^
ofAkutan To. Cie&
6.4
Documentation of Procedures ............
15
6.4.1
Operating Procedures .................................................................... .. .
............................................. 15
6.42
Monitoring Data .......................... ............................................................................................
... 15
6.4.3
Maintenance Procedures ........................................................................
..................................... 15
6.4.4
Emergency Action Plan ................ ....................................................
......... ................................ 15
65
Dam Inspection Summary ............................................................. .
............. . ............. ............ 16
Section 7 Conclusions and Recommendations ... ........... ............ ............
. .............. . ................. ...... 17
7.0
Conclusions ... .............................................................. ... . ...........
.. . ........... . . ....................... 17
7.1
Recommendations for Additional Work ..........................................................................................
18
7.2
Interim Measures ....................... --
1�
LIST OF TABLES
Table 2-1. Permitting and correspondence history for Akutan Town Creek Dam .......................................6
Table 6- 1. Summary of Dam Inspection Results .................................................................. .................. 16
APPENDICES
Appendix A Photographs
Appendix B Visual Inspection Checklist
Appendix C Information Regarding Hazard Classification
Appendix D Drawings
Dtaft Periodic Safety Inspection Page iii Juee, 1,2011
PROJECT DATA SHEET
A. GENERAL
OwnName .........................................................
..................... ....................................... AkuanHydro Data
N&DNumber ............ ..~~~..'.-~..~...`^~~.~~~..~....'---....AK'00264
HazardPotential Class .......................................................................................................................
class O
Purpose ....................................... -............................................
...... l508Wou+ot-tko-rivcrhydroelectric
YewBuilt .,,,,...,.~~.,~,,,,.,_,~~.,~,..._,,,.,..,^_.~....-'........^
.~~.....lu9}
Location ................................ ...........
..... ........... ... 54^8'33.Yy"North lui,l65»46`1633" West Louu.
Reservoir Name ,........~..--.~~.~~..^~~~.....~~..,-.......~~.UN0����8`
RivermCreek Name ....................................
..................................... ................. ................... Town Creek
Owner ^^...^^^..^^^....^^~.^......^^^^^^..
.^~^^^^~^-~^^'~`.~~..~''.... City of&kutan,Alaska
T�
'�^-...~..^...~--.~~~~^.~~~~.`.~~~~....~..-.~.....BmthG|ln4ihcetpi|oo
Core Type ~' ~~~^.^.~^~~^^~~~--~~~^^.^~~~^.^~~~^^.,.........'PVC
skcdpile
Lo�(loxth,~........~..~~........~...-205te�(KfF:
Sbmu|ou��VYUoou/l9Y3)�feet
CrestWidth .^^^-~.^~^-`^^~^-.'^~~^'.^~~--
...................................................... <2feet
Crest Elevation ^^-~.^~~~-^~~'`~.~
--- -~~~~-~^^~^...................................... ^820feet
Crest Height ...'.................'~....--,.~~......~
........................ ......... (from 0:toe) `2Afeet
C. SPILLWAY
T�
'� .-..~..,`~..~-~~.~-,~~.^^~~.^-...~....~.}-l0
inch diameter BC8`6pipes
Location ~~,.~~~~-.~~,.~.~-~...~^-..~'^,.~.~-......~.-'.CcuterofCbu/
Spillway ' ^ -~~~^^-~~~^^.~~~--~~~-~~~-~~^~-...,...`8l?6et
TopWidth ~,~,,_,~,~_~~~__~~~_~,,~^,,~~__,,,_`~.-.~..-...04feet
BottomWidth ~,^_~~~~_,~~^.,~,~,,,~~,..........................
... ....... ...... ........... NA feet
Louo�
, -.~~--`~~^-~.^^-~~~~^-~~~`~~~~-.~~^^-^^^~.......~...l00G:et
Discharge Capacity /tDam Crest Ave .........................................................
-.......................... 20o6(nuux)
D. EMERGENCY SPILLWAY
o�. Type .~~. ~~~'~.^^-~~.~~~~^.~~~-. ^^`~~^
~~~~^~^.....� y�0oc
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Location
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way
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Length �--~�~-~~~-^~^~^.~~~`~.~~`~^~.~-~~~~^~-~~^.........
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City of Akutan
Town Crock Hydroelectric Project
E. OUTLET WORKS/PENSTOCK
f—
Type - ..................... ................................................
. ......................................................... RDPE Pipe
Location........................... ............................
......................... ............................................. At main dam
Inlet Invert Elevation ...... .................................................................................................
. Not surveyed feet
r.
Outlet Invert Elevation (Penstock) ..............................
26 MSH feet (Penstock); 800 feet (Low Level Con.)
Diameter.............................................................
........... ........ . . .................................. 10 inches (for both)
Length ......................................................................
3,300 feet (Penstock); 100 feet (for Low Level Cond.)
Outlet Type ................................. _ ......................................
........................... HDPE Pipe (for both at dam)
Discharge Capacity at Dam Crest .................
...................................... ................................ 6.6 cla
..............
F. RESERVOIR
Normal Water Surface Elevation ...........................................................
-817 feet (from Topographic map)
Normal Storage Capacity ............ ..........
. ........... .............. ....... 10.2 acre-feet (estimated - Ag HE - 590)
Maximum Water Surface Elevation ....................................
-820 feet (estimated with dam base at 800 feet)
Maximum Storage Capacity .........................................................
13.6 acre-feet (estimated- Ag RB - 590)
Maximum Surface Area at Dam Crest ............................
............. ........... ..... ............................ - 1.7 acres
Surface Area at Spillway Crest ..............
............................................... - ........... - .................... , 1.5 acres
G. HYDROLOGY
Drainage Basin Area ...............................
20 acres upstream of dam; 410 acres overall for entire Watershed
Average Annual Rainfall ....................................................
96 inches at basin, 60 inches at sea level inches
100 Year/24 Hour Rainfall ...................................................................
. ... ................................. 8.7 inches
100 Year Flood .............................. . .
............................... 8-12 efs (variance based on methods -see text)
Probable Maximum Precipitation ........................................................
....................................... 22 inches
ProbableMaximum Flood .................................................................................................
- Not Determined
Floodof Record .............................................................................
.............................. No gaging record
InflowDesign Flood ...............................................................
........ . ... ........................ Not Determined
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Draft Periodic Safety Inspection
Page V Jan. 1, 2011
City of Akatan Town Creek Hydroelectric Project
SECTION 1
INTRODUCTION
1.0 Location and Ownership
The Akutan Town Creek Hydro Data is owned by the City of Akuum (City), Alaska. The Dam is located
on Akutan Island approximately 4,000 feet (ft) north of the City in the SW 1/4 of Section 2 in Township
70 South and Range 112 West based on the - Seward Meridian. The latitude and longitude are 54o
8'33.79"N, 165°4626.33"W- World Geodetic System of 1984 WGS84.
1.1 Scope
The City received notice of a requirement for dam inspection of the Town Creek Hydropower Dam on
January 25, 2010 by the Alaska Dam Safety Unit. Dan Axness of McMillen, LLC (McMillen) called
Charles F. Cobb, PE (State Dam Safety Engineer) to discuss the requirement for the dam inspection. Mr.
Cobb explained the that he had visited the dam several years ago and determined the Town Creek Dam to
fall under jurisdiction of Dam Safety due to the dam's height. Mr. Axness and Mr. Cobb discussed the
available dam design and construction information and the impact on performing a dam inspection. Mr.
Axness at the direction of Mort McMillen did a follow-up visual inspection in September of 2010.
Mr. Cobb recommended following the procedure in the Guidelines for Cooperation with the Alaska Dam
Safety Program. Mr. Cobb and Mr. Axness discussed performing the dam inspection as part of
maintenance to the dam (valve replacement, spillway modifications etc.). In addition, surveying the dam,
spillways and storage area will provide a base record of the condition of the dam, spillways and reservoir
area.
An outline of the draft report was transmitted to Mr. Charles Cobb, State Dam Safety Engineer of Alaska
Department of Natural Resources, March 23, 2011. Mr. Cobb approved the outline contingent upon
further elaboration of the existing spillway capacity, stability, seepage and other topics as presented in the
Guidelines for Cooperation with the Alaska Data Safety Program. A revised version was submitted on
April 18'". This revision represents a final version consisting of responses and revisions based on the
comments received on the April 180 draft. The extent of the original inspection consisted of visually
inspecting the dam surface and the condition of the spillway from the surface.
1.2 Project Description
The Town Creek Hydro Dam components and features include:
. Main impoundment dam and reservoir
. Diversion structures
. Penstocks
. Hydroelectric Components
These features are described in greater detail below.
^ noun Pend¢ Safety Inspection Page 1 June I, 2011
City of Akulan Town Creek Hydrodectdc Project
^
r
1.2.1 Main Impoundment Dam and Reservoir
^. The main impoundment dam base is located at approximately 800 It above mean sea level (amsl). The
dam is located within a small basin that is formed by the surrounding ridges and a flat valley. The
l' approximate size of the reservoir is 1.7 acres. The entire Town Creek watershed basins total
r.. approximately 410 acres. However, the watershed area above the main impoundment is much smaller, on
the order of 20 acres (based on GPS traverse and confirmed via watershed delineation (Appendix E).
Drawings 3 through 5 provide schematic illustrations for the dam and surrounding area (Appendix D).
r
The dam consists of compacted earth fill with a cutoff wall of a polyvinyl chloride (PVC) sheet pile
installed in an excavated area of the existing stream. An woven geotextile liner, that was possibly coated,
r^ was placed on the upstream side of the sheet pile wall and drainage fabric was placed on the downstream
^ side to collect seepage water. The fill of the dam appears to consist of soil with considerable sands and
gravels with approximately 22% silt (Appendix E). Both a sample of fill (sieve graph provided Appendix
r- E) and past reports descriptions (for example see Polar Consult, p. 3; 1985: scanned page 3 added at end
of Appendix E) indicate the soil is made up of small gravels and sand with considerable silt content. A
schematic of the layout for the dam is given in Appendix D (Drawings 3-5 . A perforated pipe is installed
� at the downstream base to collect seepage and transport it to the toe of the dam. Compacted earth
embankments were placed on both sides of the sheet pile for support. Rock riprap was placed on the face
of the slope to prevent erosion. The data is approximately 20-ft high, 200-ft long, and 12-ft wide at the
l' crest. Pictures of the Dam and associated features can be viewed in Appendix A photographs 1-18.
^ The spillway is located at the top of the dam and consists of three, 10-inch diameter high density
^ polyethylene (HDPE) pipes (Appendix A photographs 11 inlet and 12 outlet). The openings to the
,.. spillways are not screened and are subject to clogging from debris and ice (however, there is no evidence
that this happened on the main impoundment). There are no shutoff valves or covers associated with the
^ spillway. The outlet of the spillway is at the toe of the data with rock gabion placed near the outlet to
^ dissipate energy.
The intake to the penstock is estimated to be located approximately 8 ft below the full pool level of the
reservoir. The penstock intake may be sluiced by opening a valve on a tee or Wye that discharges flow
and sediment back to Town Creek. There is an additional 10-inch HDPE pipe that outlets next to the
three spillway pipes. The function of this pipe is unknown. There is a drain pipe right next to it so it is
r— uncertain whether this is another drain pipe or if this pipe represents the outlet for a low level conduit.
However, no sign of a valve was found, so its function remains a mystery because there are no as -built
r drawings. The presence of a sluice and pipe on the Penstock would argue that it represents the only low
r— level outlet on the data. There is considerable seepage (or leakage) coming out of this pipe (about Ya efs;
photograph 3). In the drawings, this pipe is referred to as a low level conduit but the extent and nature of
this pipe is unknown.
^
1.2.2 Diversion Dams
Three small diversion dams are located in streams adjacent to the main impoundment dam (Drawing 3).
^ These diversion dams transfer water to the main impoundment reservoir. Each data is approximately 5-ft
tall and has a 10-ft wide crest. The dam surfaces are covered with rock gabions shaped to allow excess
^ water flow over the dam. Geotextile is placed under the gabion baskets. The water from the most
western diversion dam flows to the central diversion dam in a 6-inch HDPE pipe. Water from the central
diversion dam and water from the most westem diversion dam flows in a 6-inch HDPE pipe to the Town
_ Creek Hydro Data reservoir. Water from the east diversion dam flows through a 6-inch HDPE pipe to the
Brett Periodic Safety Inspection Page 2 June I, 2011
City ofAkutau Town Creek Hydroelectric Project
r-
Town Creek Hydropower Dam reservoir as well. Each of the three small diversion dams has an
unscrewed intake and a butterfly valve is located immediately downstream of each of the intakes to
control water flow from the diversion dams. A 10-inch HDPE pipe spillway is located at the top of each
of the diversion dams and extends to the toe of the dam. Most of the water that supplies the main
impoundment is supplied by the three diversion dams. Photos of several of these diversion features are in
Appendix A (photographs 26-30).
1.2.3 Penstock
The penstock from the main dam (approximate data toe elevation 800 It msl) is a 10-inch HDPE within
the dam cross-section with anchored steel pipe downslope from the dam. The pipe is approximately
3,300 it long, dropping approximately 765 vertical ft to the powerhouse. The location of the penstock is
illustrated in Drawing 3 (Appendix D). The penstock has three valves: the first two located immediately
downstream of the intake and the third immediately upstream of the powerhouse. The first valve appears
to be a shutoff valve; the second valve appears to be used for sluicing sediment from the penstock. The
third valve, at the powerhouse, is a final shutoff valve.
1.2.4 Low Level Conduit
The outlet for a 10 inch-HDPE low level conduit (or toe drainpipe) is just to the right side (facing the
dam) of the three 10-inch HDPE spillway outlet pipes at the toe of the dam (see photographs 1-3 in
Appendix A). If it is a low level conduit, since it was submerged the exact location for the inlet could not
be determined. No sign of an upstream slide gate works or any other valve structure was found.
1.3 Hazard Potential Classification Review
The Alaska Dam Safety Guidelines for Hazard Classification are provided in Guidelines for Cooperation
with the Alaska Data Safety Program (2005). A class 11(significant) hazard potential was assigned by
ADNR in 2001. After discussions with the Alaska DNR, it is recommended that the Town Creek Dam be
maintained as a Class 11(significant) hazard potential due to downstream infrastructure (school and water
treatment facility). Some calculations to support the Class 11 rating are given in Appendix C.
Downstream infrastructure includes a schoolhouse, bridge and water treatment facility located
approximately 4,000 ft downstream of the dam.
Dom Penodu; Safety Inspection Page 3 June I, 2011
^
^ City of Akutan Town Creek Hydroelectric Projee
fn
r
SECTION 2
r HISTORY
2.0 History
^
�. Akutan, Alaska is located in the Aleutian Islands chain. The City entered into an agreement with Alaska
Power Systems (APS) for the construction and operation of the Town Creek Hydroelectric Project in
1990. Three small diversion dams were constructed in various streams to divert water to a main
r. impoundment dam in the Town Creek watershed located above the City. The collected water was piped
^
down the hill to a hydropower generation facility that provides electricity to the City.
^- 2.1 General Background
^ The dam site and turbine site were used from the 1900's to the 1960's. Very little documentation exists
about this era or the current construction. The first reports collected were written in 1980 by Ott Water
^ Engineers. These reports were followed by other pre -design and feasibility analyses. Prior to construction
of the current dam, there was a smaller diversion dam at the site.
2.2 Construction History
^ The Akutan Town Creek Hydro Dam and power system were constructed by Alaska Power Systems
^, (APS). The City and APS entered into ajoint venture named Akutan Hydro Joint Venture. Little is
known concerning construction means and methods, compaction test results, depth to bedrock or
^ inspection. The external configuration does generally reflect the figures found in Ott Water Engineers
., Preliminary Design Report, 1980 and other reports include a dam cross section prepared by Shannon and
Wilson. According to the City, more complete construction records were confiscated in a bankruptcy
^ dispute by a bank.
^
There is limited documentation of the construction of the main impoundment dam, diversion dams and
^ penstock in the above referenced documents. However, based on transmittals in Table 2-1, construction
�- was completed in 1993. Especially important in documenting this are the two letters from John Theide.
^ The ASTF Grant Agreement contained information on the original powerhouse P equipment, but does not
.� reflect the current equipment arrangement The documents reviewed included conceptual dam design
information performed by Shannon & Wilson. This information is more schematic in nature with respect
^ to the dams and does not show the location of the intake screens, penstock and valves, and related
�- equipment. Photographs of the site are located in Appendix A but only contain inspection photographs
^ over the last 2 years. No construction photographs were found.
" 2.3 Design History
The Akutan Town Creek Hydro Dam and power system final design, construction plans, specifications
and design report are not available. These documents were also confiscated in the bankruptcy dispute
described above. At least two reports have been developed over several years. These reports include:
• Akutan Hydropower, Preliminary Design Report, Ott Water Engineers, 1980.
• Akutan Hydropower Feasibility Study, HDR/Ott Water Engineers and Dryen & LaRue, 1989.
.. • EPS, City of Akutan Hydm Inspection Report & Upgrade Cost Estimates, May 2003.
Dreg Penodic Safety Inspection Page 4 June 1 2011
City ofAkum Town Cmek Hydroelectric Project
In addition, several grant applications have been submitted to study this project, the grant requests
include:
• Alaska Power Systems, ASTF Grant Agreement 92-4-277, Unitized Village Scale Hydro -diesel
Generation System, April 1994.
• Egor Eispov, LCMF Inc., Alaska Energy Authority, Akutan Rural Power System Upgrade, 2007.
• Grant Application of Akutan Hydroelectric System Repair, City of Akutan, Renewable Energy
Fund Grant Application, AEA-09-004, September 3, 2008.
The permitting process does provide an approximate schedule of the design/pre-construction history as
shown in Table 2-1.
The dam appears to have been permitted to have been constructed as a 14-foot high dam. We have not
been able to find any documentation that resembles construction plans for either the 14-Foot high
proposed dam or the 21-foot high constructed data.
2.4 Inspection History
The dam has been inspected twice since construction. One inspection was completed September 8ih and
9'", 2010. The results of that inspection are included in this report. Otherwise, the dam had a "limited
field inspection" by Mr. Charles Cobb on June 19, 2001 for data safety permit requirements. The dam
was found to have an initial Hazard Classification of Class 11(signifiicant).
Draft
Page 5
June 1. 2011
Diversion Dam #2
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Diversion Dam #3
Turbine hydraulics and load bank
Turbine control panel
Turbine load bank controls
r-
r^ Turbine runner