Loading...
HomeMy WebLinkAboutHydropower Potential of Windy River for Seldovia Alaska 1984'1K 1425 545 H94 1984 HYDROPOWER POTENTIAL OF WINDY RIVER FOR SELDOVIA, ALASKA AUGUST, 1984 AU\SK':\ RESOURCES liBRARY AUG 1 2 1994 Figure No. 1 2 3 4 5 6 7 8 9 10 11 Table No. 1 2 3 LIST OF FIGURES Title Location Map Seldovia Economic Base Seldovia Energy Forecast Flow/Duration Curve Energy Use versus Energy Potential Diversion Structure Layout of Facilities Dam Site Layout Penstock Profile Damaged Bridge on Jakolof Bay Road Homer Tie-Line Intercept LIST OF TABLES Projected Population Growth Comparison of Population Growth Rates Estimated Windy River Flows Page 2 ~ 14 19 21 n n 24 26 29 31 Page 17 13 19 HYDROPOWER POTENTIAL OF WINDY RIVER FOR SELDOVIA, ALASKA AUGUST, 1984 INTRODUCTION The evaluation of small hydroelectric systems was authorized bv a 1 October 1976 United States Senate Resolution, which directed the U.S. Army Corps of Engineers to determine the feasibility of installing small prepackaged hydroelectric units in isolated Alaska communities. In 1982, a regional inventory for small hydropower projects in Southcentral Alaska was completed for the Alaska District by Ebasco Services, Incorporated. This inventory analyzed more than 30 sites, recommenrling nearly 20 for more detailed examination, including the Windy River site. The Windy River site was one of six selected by the A.laska Oistrict from this group for field reconnaissance and additional analysis. Ouring 20-73 Septemher 1982, an interdisciplinary study team from the Alaska J)istrict conductE'rl a field reconnaissance of the Windy River site. The site was felt to have sufficient potential to offset power losses during transmission line outages, and therefore warranted further study. .A.dditional site visits were marle on 2q November 1983 by personnel from the Alaska District, and on 27 April 19<1,t~ hv Alaska District and S & S Engineers, Inc. personnel. -I - FIGURE 1 SELDOVIA AND VICIN rTY MAIN TRANS. LIN E THREE-PHASE TAP _._.- (ALL EXISTING LINES ARE 14.4/24.9 kV, 3~,4W) o 2 5 4 5 f ," I SCALE IN M'LIS EXISTING CONDITIONS Seldovia is located on the west coast of the Kenai Peninsula, on the east shore of Seldovia Bay, 16 miles southwest of Homer, in the Chugach Mountains. It is in the Kenai Peninsula Borough and the Kenai-Cook Inlet Census District. Seldovia's population has varied considerably since its modern founding in the first half of the 19th century. Durin~ its history, Seldovia's fortunes have risen and fallen on the success of its major enterprises. In the 19th centurv, sea otter hunting was a major activity. In the first half of this century salmon fishing became prominent, with as many as four canneries operating in the community. In 1950 the population stood at 437. By the mid-1950's salmon harvests had declined, two of the salmon canneries closed, and the DODulation began to decrease. At about this time, king crab fishing became an important activity. The population began to grow again, reaching 460 persons in 1960 and an estimated 550 in 1964. In that year, however, the Good Friday Earthquake struck, sinking land in the area by 3.7 feet. Commercial and industrial buildings along the waterfront were hardest hit, and many closed. An urban renewal project rebuilt the waterfront, but only one of the original four canneries was rebuilt. Population dropped temporarily as some residents moved awav in search of better employment opportunities. By 1970, however, improving prosperitv caused population to increase again to 437. - 3 - ,.... A comprehensive plan prepared in 1969 by the Alasl<a ~tate I-\ousing Authority contained two sets of population projections. One assumed that Seldovia would not grow ("Continuation of Status Quo"), while the second ("Economic Development") predicted that the community would grow to 470 in 1975 if king crab and tanner crab harvests increased, shrimp prorluction began at the Wakefield plant, and tourism and/or timber expanded into major "basic" industries. Comparison with actual growth experienced by the community indicates that the short-term "economic development" projection has proved fairly accurate. In fact, tanner crab harvesting and processing have become important, and shrimp processing recently began on a limited scale. Log harvesting also increased, and a sawmill at Jakolof Bay became an important employer. Accordingly, the city's population grew, exceeding the projected 1975 population level. In 1978, despite population declines associated with closure of the Jakolof Bay sawmill, a special census recorded the city's population at 485 persons, with an additional 99 persons residing outside of city limits but within the Seldovia voting precinct (Kenai Peninsula Borough, 1979). The overall growth in the city's population from 1970 to 1978 averaged 1.3 percent per year, a very moderate growth rate. The present population is still about 500. POPULA TION CHARACTERISTICS Many Seldovia residents have lived there for manv years. Communitv stability is reflected by the fact that the median age of the city was near Iv ~9 years in 1970, compared to 28 years for the nation as a whole and 21 vears for Alaska during the same year. Nearly one-third of the population was Native, and over 60 percent of all resirlents were male. After 1970 Selrlovia's population characteristics changen consirif'raf)lv, despite little apparent chan~e in total population. \~ost of the changes are quite similar to those experienced by larger, growing Alaskan communities. As measured by the 1978 Special Census, Native oopulation has remained at 138 persons, while non-Natives increased by 48. As a result, the percent of population which is Native fell from 31.6 to 28.5 percent. Median age fell significantly, from 28.9 to 27.n years. This was apparently caused by in-migration of a significant number of young adults (ages 25 to 34 years). Although not falling in absolute size, the relative proportion of residents age 45 or more fell during the same period. ECONOMIC BASE A direct survey was conducted of representative employers and self- employed persons in Seldovia during the summer of 1979. This survey was used to compile the employment and economic base analysis shown in Figure 2. Seldovia's employment shows a great deal of stability over the course of the year compared to many Alaskan communities. Of course, much of this is due to the fact that fishing, the major economic activitv, continues throughout much of the year, and that many residents engage in two or more income- earning activities during the course of a year (for example, construction anrl fishing). -') - 150 Jobs (77%) Other Trade &. Gov't Fish Processing Fishing BASIC EMPLOYMENT 45 Jobs (23%) Other Trade Government SECONOARY E,"'~PLovJ\~FNT FIGURE 2. SELDOVIA ECONOMIC PlASE (t 979) Source: Pacific Rim Planners, Inc. The largest employers in town and their ernDlovment are: EMPLOYER NAME MANUF ACTORING EMPLOYMENT pR.OnUCT Wakefield Fisheries 35-60 Seafood Products South Central Tim ber Dev. Co., Inc. 10 Wood Prorlucts Christian Logging Co. 10 Logging NON-MANUFACTURING Bay View 7 Reta; 1 Standard Oil of California 2 Petroleum Products - 6 - Seldovia has a relatively large number of secondarv jobs (about 4 S) compared with other communities of similar size. The community's basic to secondary employment ratio of 1.00 to 0.30 (meaning that 3 1/3 basic jobs support roughly one secondary job) is usually found in somewhat lar~er communities of 1,000 or more population. It is likely that at least part of the reason for this relatively high state of economic development is that some residents have earned enough income in other pursuits (pipeline construction or fishing, for example) to enable them to establish a business. Fishing and fishing-related jobs are still clearly the major sources of employment in the study area. Fishing, fish processing and indirect (secondary) employment attributable to the two categories account for 85 percent, or more than four out of five, of all present jobs. ELECTRICAL POWER Electrical power is currently supplied to Seldovia by Homer Electric Association (HEA) via the transmission line running from China Poot Bay to Seldovia. HEA purchases its power from Chugach Electric Association (CEA). Of the total power metered at the Seldovia Substation, the communities of Port Graham and English Bay each use 10-1'5%. A typical household uses 500 kilowatt-hours (kWh) per month and has a monthly bill of $ 35 to ~40. Households have a fairly complete range of appliances. If the price of electricity were reduced, it could be expected that per capita consumption might remain relatively unchanged. Homes are heated by wood stove or oil burners. A typical annual heating bill based on oil burners is $1,000. Residential customers account for 36% of the total Seldovia demand, large commercial 29%, small commercial 17%, and public buildin~s 18%. The transmission line cuts a swath through areas which are heavily wooded and of varying topography. Power interruptions due to falling trees and blowing limbs have been frequent. Much of this problem may be attributed to inadequate maintenance of the right-of-way. Transmission lines are sometimes down for extended periods of time, especiallY during the winter, and HEA has estimated an overall reliability factor of approximately 60%. Seldovia maintains standby diesel generation, however, and actual power-out time is quite brief, having been estimated by the local HEA representative as totalling only 176 hours in 1983. This can probably be considered typical. The standby diesel generation consists of one 30n-kW and three 600-kW generators. These are maintained and operated directlv I)y the HEA representative and HEA purchases all fuel for their operations; thus, no direct costs are incurred by the City of Seldovia. FUTURE CONDITIONS The major force which might affect Seldovia's economv would he development of the Lower Cook Inlet oil fields as part of the Outer Continental Shelf (OCS) activities. Depending on the level of finds and the timing of development and siting of onshore service bases, UP to 7.92 OCS- related employees might move to the Seldovia area in the future. The intermediate range number would be 37 to 74 employees. OCS emplovees would, in turn, encourage growth in secondary employment by purchasing local goods and services. Other employment growth might also be stimulated through growth in the fisheries, tourism and wood products industries. The two canneries presently in operation may begin to cut back, with one revamping for processing bottom fish. An additional factor which could affect the growth rate would be the reopening of the chromium mines at Red Mountain; however, that possibility is not quantifiable at this time. Possible changes in Selrlovia's economy during the next two decades can be depicted by constructing three possible outcomes, or scenarios. The scenarios (low, intermediate, high) indicate the range of potential outcomes. They demonstrate the effects of external events outside of the control of the community (such as the outcome of oil exploration in Lower Cook Inlet) as well as the effects of actions the community may take (such as providing suitable accommodations for a developing bottom fish industrv). !=.ach scenario assumes a particular combination of external and community- influenced events. These projections were made bv Pacific Rim Planners, Inc. in 1979. The population in Seldovia is still around 500. Since OCC; development has not yet occurred, growth rates for the three scenarios were "shifted" 5 years. The years in brackets reflect the original predictions made by Pacific Rim. Under the low scenario, area employment is projected to increase bv only 27 jobs. Under the intermediate scenario moderate scale OCS development, in addition to fishing and fish processing eXDansion, would stimulate increases in other sectors of Seldovia's economy, causing total employment to grow by an annual average rate of 3.2 percent per year. ocs- related employment would be highest during the period 1987-1992 (t 982-1 9~7), when construction of OCS drilling platforms and related facilities woulrl occur. OCS-related employment would peak at 74 in 1982 (19~7) and decline to 17 bv 1996 (1991). Under the high scenario, major development of the Lower Cook Inlet oil fields, nearby location of related onshore facilities, and major expansion anrl diversification of Seldovia-based fishing and fish processing activities would - 9 - cause major growth in all categories of Seldovia's employment, averaging 5.9 percent per year from 1984 to 2005 (1979 to 2000). OCS-related emplovment would increase rapidly during the late 1 no's and early 1990's, coinciding with construction of drilling platforms and related facilities, reaching a maximum of 292 Seldovia-based workers in 1988 (1983), and falling slowlv to a production level of 145 johs. Other employment growth would probablv occur more evenly throughout the period. FUTURE POPULATION Tables 1 and 2 present population projections for the planning area for the year 2005. The projections are based on the employment scenarios discussed in the preceding section and projected labor force participation rates. For the sake of clarity, the projections are divided into direct OCS- related population (OCS workers and their families) and other residents for each of the three scenarios. The low scenario projects continued growth, but at a maximum rate of 70 percent lower than the 1970-1978 growth rate. Under this scenario, no OCS-related households would reside in the area. Total population in the vear 2005 would be 542, for an average annual increase of 0.4%. In the intermediate scenario Seldovia would grow an average of 2. q percent per year, more than double the area's 1970-19n growth rate of '.'3 percent. Population growth rates would be very high during the second half of the 1980's as oil fields are developed, and would drop to fairlv moderate rates by the early 1990's. Total population in the year 2005 would be 913, nearlv double the estimated 1978 population. If the high scenario were to occur, the population would incrf"as(' dramatically during the second half of the 19~ors, coinciding with OC<::' development. Following completion of development, population would decrease temporarily for the remainder of the decade, but near the turn of the century would return to a growth rate about twice the 1970-1978 rates. Total population in the year 2005 would be 1,517, or roughly three times the present population. This threefold increase translates to an average annual growth rate of 5.4 percent. By comparison, recent pooulation projections for southcentral Alaska estimate growth rates ran~ing from 2.g to 5.0 percent, with an intermediate estimate of 3.7 percent, for the same period (Scott, 1979). Hence, projected Seldovia growth rates represent a wider ran~e, with an intermediate or mid- range estimate only slightly lower than the regional average. -11 - TARLF.l PROJECTED POPULATION GROWTH F\Y SCENARIO 1984 to 2005 LOW INTER~~Ef)IATE l-\ 1 G l-\ Non OCS-OCS-Total Non OCS-OCS-Total Non OCS-O~S-Total Related Related Related Related Related Relaterl 1984 500 0 500 500 0 '500 500 0 '50f) 1985 505 0 505 525 1(; 541 576 ,'5 ,; t I 1986 505 0 505 538 10 54~ (;10 ,?f)9 ~19 1987 506 0 506 562 45 1')07 635 749 ~~4 1988 504 0 504 575 63 ';38 65, "'24 977 1989 507 0 507 592 (;(, 658 ('';0 514 t 174 1990 508 0 508 612 74 686 7?7 493 Ino 1991 505 0 505 632 rn 754 7(,9 516 12~5 1992 506 0 506 642 148 '790 786 46~ !?54 1993 506 0 506 650 100 750 798 160 1 1.'58 1994 507 0 507 659 94 75, ~14 326 114n 1995 512 0 512 669 86 755 855 300 I 1 '55 1996 510 0 510 686 80 766 883 790 1173 1997 515 0 515 708 74 782 925 790 l? 1 '5 1998 520 0 520 722 74 796 956 790 174'; 1999 522 0 522 739 74 813 991 79f) I?~ I 2000 527 0 527 754 74 828 1077 290 1117 2001 527 0 527 766 74 840 1064 79f) " '54 2002 532 0 532 7'J.6 74 860 1098 29f) 1"'88 2003 539 0 539 803 74 877 1142 790 14.,,7 2004 539 0 539 817 74 891 lun 79f) 1471 2005 542 0 542 839 74 913 12?7 29f) 1 '517 Source: Pacific Rim Planners, Inc. Excludes seasonal residents. Years shown are five years later than in Pacific Rim study. -12 - PERIOD 1984-1987 1987-1990 1990-1993 1993-1996 1996-1999 1999-2002 2002-2005 Average Yearly Rate For Period 1984-2005 TARLf: 2 COMPARISON OF POPULATION GROWTH RATf:S IN PROJECTEO POPULATION p, Y S(:f:NA R 10 LOW SCENA RIO 0.4% 0.1% -0.1% 0.3% 0.8% 0.6% 0.6% 0.4% INTERME[)IATE SCENARIO 6.7Q(., 4.2% 3.()% 0.7% 2.()% 1.9% 2.0% 2.9% HIGH S(:FNARIO 20. qQ(., 1 l. 1 Q(., -1.7% 0.4% 3.r)Q(., 2,70.; 1. no.; 5.4% Source: Pacific Rim Planners, Inc. Estimates based on Environmental Services, Ltd. (1979) and CH2M-Hill (1978). Excludes seasonal residents. NOTE: Rates given are annual averages for the 3-vear periods. Original forecasts have been shifted 5 years into the future. FUTURE ENERGY DEMAND Future energy demand would closely parallel population growth. Figure 1 shows historical energy use (1970 through 1981) and three growth curves, haser! on the rates in Table 2. Post-2005 rates were evaluated as one-half the rate for the period 2002-2005. The resulting annual equivalent rlemands for the project life 1995-2045 were 4,100; 7,000; and 11,600 I\~Wh for the low, intermediate, and high scenarios, respectively. Projections made by others are consistent with the curves in Figure 1. Energy forecasts by Chugach Electric Association through 1997 (I q~n) inrlicate an average annual increase of energy demand of 3.3%, hased on a morlerate growth assumption. Homer Electric Association expects the Selrlovia rlemanrl to remain relatively constant and considers a 1% annual increase the ahsolute maximum. , / / ,,1J()6 / 11 100 / / / /,(If'N / 1"'~IIIf' 13'IIeflf' 1,Nt? l #~ ~ "tk? ¢Nt:? / _--------~~~--Z--------------------- ,.,1fN? FIGURE 3, SELDOVIA ENERGY FORECAST SITE INFORMATION LAND OWNERSHIP The Windy River site is on Native holdings under two separate interim conveyances, as provided in the Alaska Native Claims Settlement Act; the surface estate was conveyed to Seldovia Native Association, Inc. (village corporation), and the subsurface estate to the Cook Inlet Native Association, Inc. (regional corporation). Patents will be issued in lieu of the interim conveyances once the parcel is surveyed. The existing road from its junction with Jakolof Bay Road to the mines upstream of the Winrlv River site is within a 60-foot public easement and is subject to Federal and Stat~ laws and regulations. The Seldovia Native Association has orallv endorserl the Droject. REGIONAL GEOLOGY The site is located in the Kenai Mountains, on the south side of Kachemak Bay. The Kenai Mountains are part of the Pacific "order Ran~es Physiographic Province of Alaska, and together with the Chu~ach Mountains to the east, they form an arcuate mountain barrier around the northern coast of the Gulf of Alaska. Glaciers have eroded the mountains into a ru~ged topography characterized by horns, cirques, and deep U-shaped valleys. The Kenai Mountains above an elevation of about 3,000 feet are mostly buried by icefields, except for scattered peaks which protrude above the ice. Vallev glaciers, present in the upper reaches of most of the valleys, are a major water source for rivers, lakes and streams on the lower Kenai Mountain slopes. Thick sequences of upper Mesozoic metasedimentary and metavolcanic rocks are exposed in the Kenai Mountains. These units are informally referred to as the "Chugach Terrain" in the adjacent Chugach Mountains. Researchers have interpreted the rocks of the "Chugach Terrain" as having been deposited in deep water on the margin of the continent, either on a continental rise or in a submarine trench. The "Chugach Terrain" is subdivided into a assembla~e of metac1astic and metavolcanic rocks of presumed late Jurassic and/or Cretaceous age named the McHugh Complex, and late Cretaceous deoosits correlated with the Valdez Group. The rocks of the Kenai Mountains have been highly deformed into a complex system of folds and various types of faultin~, which resulted from a long history of active compressional forces associated with the boundary -15 - between the Pacific and North American plates. In spite of this complexity, there exists an overall structural grain which is roughly parallel to the northeast trending mountain ranges and best expressed in the foliation and bedding attitudes of rocks. The two primary types are fine-to-medium grained, weakly metamorphosed graywacke and foliated aq~illite. A minor amount of interbedded metaconglomerate is associated with the argillite and graywacke. Of lesser importance in the McHugh Complex are occasional beds of gray limestone and greenish gray metavolcanic rocks. Mapping in the McHugh Complex is extremely difficult due to the lack of marker horizons in the massive graywacke units and the lack of continuity of individual beds. Mapping is further complicated by the faulting and folding of the area. Mapping in the area has been done on a scale of 1:250,000 with little emphasis on structure. The graywacke, primarily consisting of feldspar grains in a clay- size matrix, is massiye and very hard. The graywacke also contains amounts of quartz grains and approximately 5% or less of medium-to-coarse grained, angular dark-gray shale or argillite fragments; it is typically laced with an irregular network of hairline white quartz and brown color in outcrop due to weathering. A strong hammer blow is required to break the graywacke; it commonly fails along minute, irregularly oriented discontinuous fracture planes that have a brown to dark gray weathering stain in thin section. The graywacke occurs in thick massive bodies, with occasional interbeds of argillite or metaconglomerate, and as interbeds, lenses, boudins, and clasts within the argillite units. -16 - SITE GEOLOGY The Kenai Peninsula is located in Southcentral Alaska, a seismicaUy active region. Seismicity and design earthquake reports done for P>radlev Lake are applicable to this project. No further analysis is intended now. T)istances to known major faults include: Eagle River Thrust, 8.5 miles; Border Range, 6 miles; and Sterling, 9.5 miles. The proposed damsite is at an elevation of approximately 920, and the powerhouse at an elevation of approximately 685. Bedrock in the area is a thick bedded dark-gray metagraywacke of the Mcl-{ugh Complex. The penstock route (Figure 4) diverges from the stream's right bank and follows relatively flat slopes (I-IO%) which continue for approximately 1980 feet before descending steeply (up to 40%) for a distance of approximately 1440 feet to Jakolof Bay Road and the powerhouse site. A surficial geological review was made of a bench paralleling the stream channel for a possible penstock route. The route recommended in this report is further to the east than the previous route, but it is assumed that the geology does not differ significantly. Bedrock exposures are rare along the penstock route, hut occasional outcrops of massive graywacke are present. The powerhouse would be located on the floodplain below the Jakolof Bay Road. Foundation would be a cohble, gravel and sand mixture. HYDROLOGY Within the project area, Windy River is a steep, cascading stream mostlv confined by massive rock outcrops. The proposed damsite is bounded on the -17 - right side by a vertical rock outcrop to a height of apnroximately 15 feet high, and on the left by a more moderate slope of approximately 2n o . A gaging sit~ was established 600 feet upstream of the damsite, and at the time of the gage installation (20 September 1982) the stream width was measured at 4~.~ feet with a maximum depth of 1.4 feet. Retween the gaging site and the rlamsite the gradient varies from 2.2% to 5.3%. Below the damsite the gradient increases to 7.5%, entering a cascade-and-falls system. Frequent significant changes in stage to a heh;ht of 2 to , feet above observed flow depths are evidenced by the lack of any vegetation on the rock outcrops at the proposed damsite. Ouring the September 19~? fielrl reconnaissance, the stage rose one foot overnight during a period of light rain. Even with this rapid runoff time and increase in stage, the water remained clear, indicating little sediment transport. This is further evidenced by the lack of fines in the gravel-and-cobble streambed, tvpical of steep-gradient streams in this area. A regional analysis was performed, using measured data from similar streams in the same general area, to develop synthesized monthly flows for Windy River, which are presented in Table 3. This data was utilized to plot the exceedance curve shown in Figure 4. On 17 May 1984, the gaging site was visited by Alaska r)istrict and S N. " personnel and the gage was seryiced and the data pod replaced. The data from that period of record has been reduced and analyzerl, and has provirled an additional level of confidence in the synthesized data. -18 - --- TARLE 3 Estimated Windy River Flows Year A verage Monthly Flow, e f 5 Jan Feb Mar Apr May Jun Jul A.ug Sep Oet Nov nee A.vg. 1972 65 49 18 31 1') 17 9 73 7 5 5 9 38 85 52 19 "21 '-1 16 I 1 ?tJ. 74 9 6 6 11 55 77 30 1"2 ?7 36 31 lit ?f; 75 8 6 5 6 45 17.2 78 21 15 tJ.4 If; In 11 76 8 6 5 11 49 105 60 19 61 57 51 17 19 II 77 55 39 19 17 65 115 82 52 19 58 17 II, 7 45 78 7 7 6 8 56 104 46 19 "2'-71 79 7f, 1tJ. 79 14 9 6 14 54 89 46 37 20 86 97 'If, itl 80 12 18 11 15 72 124 74 56 40 73 ?4 1tJ. tJ.it 81 57 30 25 22 116 92 6~ 33 ?1 37 17 I~ 4f, 82 10 14 10 9 33 79 44 16 52 Avg. 19 14 10 12 58 96 57 "27 3? 57 11 17 3f, o 40 170 /00 ~ T/HG """,,~ JrQV.-9'LI..I!!!:Q OA'" c.KCEGOEO FIGURE <t! FLOW DURATION CURVE - ENVIRON"'1ENTAL SYNOPSIS Construction of a run-of-the-river project on Windy River would not have significant adverse effects on the environment. The backwater pool created bv the diversion structure would extend upstream no more than 500 feet, would he no more than 50 feet wide, and would have a maximum depth of 10 feet (at the diversion structure). No fish have been observed in the project area, and because of the prevalence of high cascading falls, provisions for a fish ladder amI minimum "fish flows" have not been considered. ENERGY ANALYSIS Assumed plant capacities for Windy River were based on maximum turbine flows of lfO, 50, and 60 cfs, which coincide with exceedance intervals of 3"1, ? 'i, and 20%. The program HynUR was used to determine the average annual outout for each of the plant capacities considered. It combines streamflow duration data and assumed plant characteristics to develop a capacity-duration curve, then intergrates the area under the curve to yield the average annual energy. For the 590, 730, and 900 kW capacities, average annual outputs of 3100, T~0(), and 3700 M Wh were calculated. It should be noted that the analvses were basecf on average monthly flow data. This tends to overestimate the power potential of the river, since extremely low flows, from which no DOwer can be produced, and extremely high flows, for which power potential is limited by the installecf plant capacity, are lost in the averaging process. The overestimation is not significant at this level of study. Figure 5 shows the temporal distributions of tVDical energv use in ~elcfovia and the energy potential of Windy River. The energy use curves are basecf on the annual equivalent demands from Figure 3 and monthly distribution factors developed from records supplied by HEA. It is obvious from the figure that Windy River could meet the demand in Seldovia for onlv a few months a veFlr, and that other sources of electricity would be called upon for the remainrfer of the year. 1000 --~\ ------.... \ -- \ \-- FIGURE 5 ENERGY USE VS. ENERGY POTENTIAL DESIGN CONSIDERATIONS LAYOUT OF FACILITIES The system would be a run-of-river facility with a diversion structure and intake at an elevation of approximately 920, and an overlanrf penstock route of approximately 34-20 feet to a powerhouse located in the Winrfv River floorfDlain at an elevation of approximately 68.5. The relationship of the facilities is shown in Figures 7 and 8. 21 - DIVE RSION STRUCTI JR E /\ structure 8 to 10 feet in height wouln be sufficient to divert flow into the maximum size penstock. A rockfilled bin structure (Figure h) is the most cost-effective alternative. The bin material can he asseml)led on-site anrl filled in place with local material. This type of structure is extremelv stal)lf' under high flows and high velocities. A 24-inch r:.1\~.P. "drain" with a l!atf'· valve would be provided in the base of the structure for maintenance ourooses. The diversion structure and intake are shown in Figur€"s {;, 7 and~. The diversion would be constructed durin!'; the months of low flow; the flow coulrl therefore be diverted from the construction area bv pumping. LfO' FIGURE' DIVERSION STRUCTURE 'il - \ \ o 500 1000 ------ FIGURE 8 DAMSITE LAYOUT o 50 100 ~_..... I --I SCALE: I" 50' INTAK NSTOCK The intake structure would consist of a 6-foot diameter Dr~cast concrete manhole with a trashracked lid. It would be located a sufficient distance upstream of the diversion structure to provide the proper alignment for the penstock route through the rock point and along the right bank of the stream. A butterfly valve would be provided at the penstock entrance. The penstock would diverge from the stream in an easterlv direction as shown in Figure 4. This would provide approximately 1,980 lineal feet of mild slope before descending at a steep slope for approximately 1,440 feet to the powerhouse. Plastic pipe would be used for the low pressure portions of the penstock, thereby allowing both a cost-saving and significantly easier construction as compared to steel pipe. The plastic pipe is thermally bonded at the joints: this jointing operation can be set up in one location, and the pipe string can then be pulled downslope from the bonding machinery to take better advantage of the topography along the penstock route. Where the slope steepens and pressure increases, the pipe material would change to steel. The penstock route intersects the 3akolof Bay Road approximately 500 feet downstream of the bridge over Windy River, and proceeds another 150 feet to the powerhouse location. The upper penstock diameter is based on maintaining an en~rgv grade line slope of less than the pipe grade (I %), and the lower diameter is based on a maximum flow rate of 10 fps. -25 - r z o f--;; W ...J W /'if/IIO C..¥7 t.~ .I",.f"E'$:SU~6 /,,/'1", /A./~ /,..~ /#'-~-~- .,P"""~TdCK .:s7A'r/t:).(/ FIGURE 9 ''''<>t7 I~ '\ ~ ~ .~ I~ .~ ;,r.-"", PROPOSED PENSTOCK PROFILE SELDOVIA SMALL HYDRO. PROJECT POWERHOUSE LAYOUT The powerhouse would be a conventional indoor plant wi th the substructure constructed of reinforced concrete and the above-grounc1 housinl' being a pre-engineered 40' x 10' x '20' metal huilding. The powerhous(' woulrl contain the turbine generating unit, controls, governors, anc1 switrr"lgf'ar. Control facilities would be for an unmannerl plant, anrl orotectiv p npvirps would operate automatically to protect the equipment. MAJOR ELECTRICAL E0Ulr\~F.NT Turbine The turbine would be a vertical-shaft multijet Peltnn tVDP, r-1tf'ri at 'inn kW. This type of turhine is compatihle with high hea.rl-Inw tiisrh3.rgp -?t, - I! '{ I~ I~ ~ ,~ I r- situations, such as that at Windy River. This type of arrangement also precludes the need for surge tanks, since the jets are simoly deflectee! from the buckets to accomodate sudden load reductions. The unit woule! he operated at part load by using a reduced number of jets. Generator The generator would be a synchronous type with a vertical shaft couoled directly to the turbine. Rating would be 750 kVA, 10, 60 Hz, 4RO volt at O.R power factor. Drip proof housing would be provided. The generator would he open-ventilated with an 800 C rise, Class P, insulation, and no provisions for overload. The generator would have full runaway speed capability. Excitation svstems would be in accordance with manufacturers standards. Power Transformers The generating station would require one, 750kVA 48nv delta/14.4-24.9KV wye, 30 transformer, OA_class with minimum non-standare! impedance. Necessary terminations, switchgear, and protective devices woule! also be provided. Load Controller The runner would have four jets. Speed control of the turbine woule! be accomplished through the needle stroke and deflector position for each of the jets. The needles and deflectors are positioned by hydraulic servomotors which are controlled by the speed governor in response to changes in load on the generator. Generator Voltage System The connection between the generators and breakers woulrl be with cable. The generator and station service breakers would be metal enclosed -27 - r '/ / drawout type rated hOG V, with 1600 am p frames. The brr>akf'rs wOllin be combined in a common switchgear lineup along with generator surge protection and instrument transformers. Unit Control and Protective Equipment Unit controls would consist of manual startup and shutdown circuits, basic protective relays, and basic instrumentation. Protective relays for each unit would include generator differential, overs peed, overvoltage and ground overcurrent. Instrumentation for each unit would include a voltmeter, an ammeter, a wattmeter, and a watthour meter. The controls would be contained in a single cabinet. No annunciation or station batterv would be provided. Station Service The station service power would be obtained via a tao between the generator breaker and the main power transformer. The station service distribution panel would be adjacent to the generator switchgear linellp. Station service power distribution would be at 480 volts 3-ohase transformed to 240/180 volts three phase and single phase power. Standby diesel generation (approximately 25 KW) sufficient to supoly station Dower needs would be provided. ACCESS The 3-mile road to the Kenai Chrome ~~ine leaves the Jakolof P,ay Road and follows the left side of the river. This road could be upgraded sufficiently to provide access to the damsite. Associated project costs would be with upgrading this road and the 3Y2-mile portion of Jakolof Bav Road from the -28 - landing site In Jakolof Ray. It would be necessarv to construct accf'SS for construction equipment alonlS the penstock route, hut the amount of equioment required for the upper portion of the penstock could he minimized if plastic pi pe is utilized, as discussed above. The bridge across Windy River has suffered severe damage and woulcf require replacement (see Figure 10). This bridge provides the only access along the Jakolof Bay Road. Maintenance for this road is the responsibilitv of the State Department of Transportation and Public Facilities. At the time of this study, several portions of the road between Seldovia and ,Jakolof Bav have washed out, and the level of maintenance is extremely low. Figure 10 Damaged Bridge On Jakolof Bav Roacf -29 - TRANSMISSION LINE The line suggested as a tie point to the Homer system is a I4.4/?4. 9K V 30 4W distribution line. Transmission from the Windy River site woulrf also he 14.4/24.9 KV 30, 4 wire. Spokesmen for HEA indicated that thev would oppose tying to that line even if proper protection devices were accomplished. It was clearly stated by HEA that transmission from the Windy River site shoulrf be fed into the Seldovia substation. Overbuild to keep the Homer tie separated from the Windy River transmission is possible and considered bv HEA to he more desirable than tying to the existing line. The distance from the site to the substation is approximately 17 miles. Two options mav be considered. Option A -Turbine at 750 kVA, driving a 750 kV A, 30, 480V svnchronous generator at 80% power factor, feeding a 750 kV A 480V 114.4-74. 9K V 30 delta-wye connected transformer. Transmission line would be If? ACSR 304-wire. This option requires a new 17-mile 30 4 wire 14.4/?4.9KV transmission line which includes 15 miles of 14.4-?4. 9KV overbuild required to reach the Seldovia substation. Option B -Assumes Homer Electric Association can be persuarfed to allow interconnection with the existing distribution line. To exercise this option, a 480V delta/24.9 KV wye 7')0 KVA 30 transformer at the generating site would be required. Appropriate protective rfevices woulrl be provided. These protective devices would he required to protect the hydro station from the grid if an outage occurs and to svnchronize and restore power after outage clearances. At minimum, the following protective devices would be installed: generator frequencv or soeerf -30 - matching device, synchronizing device, v()It.1\~f' mCltc~ing relav, directional power relaY, reverse-phase current relav, generator overcurrent relay, overvoltage relay ann generator current nifferential relay. The existing distrihution line is of sufficient caoacity to carrv full load. (Note: Option B was assumed for cost estimates, as it proved to he the least costly alternative.) SELDOVIA SUB. 14.4/24.9KV, 3(11, 4W PROPOSED (SWITCHING _r-\_-~ TRANSFER SUBSTATION HOMER SUB. __ /lr{t EXIST. 3\1, 4W, 14.4/24.9 KV DISTR IBUTION TAP TO HEAD OF JACKALOF BAY ~I!:l I V--NEW 3(1l,4W,14.4/24.9 KV ---f---------NC !, NC I I NO' _1..J~ I I =---_+-__ +-_ .. ~~ WINDY I ..........-4---~--t-/--/J SUBt :~~J EXIST. 311 DISTRIBUTION TAP FIGURE I I HOMER TIE-LINE INTERCEPT (OPTION B) -31 - NC NO = NORMALLY CLOSED NORMALLY OPEN ECONOMICS BENEFIT ANALYSIS Benefits for the Windy River project were developed by considering the next least costly alternative of providing energy to Seldovia. The production costs per kWh that can be avoided by the hydropower plant are credited to the marketable annual output of the plant. Energv supplied to HEA bv CEA is currently produced by natural gas turbines. By late 1989, however, Alaska Power Authority's 90 MW hydroelectric project at Bradlev Lake, 40 miles northeast of the Windy River site, is expected to be producing power. The project manager indicated that the energy demand of the entire Kenai Peninsula would be fully met by the Bradley Lake project until anywhere from the mid-1990's until 2006, at which time additional energy sources would be required. This coincides approximately with the power-on-line date of Windy River, through the first decade of its operation. It is assumed at this point that the Windy River plant will be displacing natural gas-produced energy throughout the project life, since this appears to be the case for at least 40 of the 50 years. In the event that it actually displaces equally inexpensive hydropower from Bradley Lake for up to 10 years, the benefits would he overestimated. Natural gas currently costs Chugach Electric Association a weighted average of $1.23 per million BTU (mBTU). In 1997 current gas purchase contracts will expire and gas costs may jump to the world orice of $3.36/mBTU. For a power-on-line date of 199.'5, a weighted present worth gas price of $3.19/mBTU is developed, which is equivalent to 50.04/kWh. Data Resources, Inc. has ascertained that the costs of natural gas and other fuels increase at a significantly higher rates than do other costs (lahor, machinery, material, etc.). This net increase in future fuel prices represents an additional cost which can be avoided by hydropower rlevelopment ann is therefore claimed as a project benefit. The relative rates of increase of natural gas and diesel costs determined by nata Resources, Inc., are as follows: Period 1983-1985 1986-1990 1991-1995 1996-2000 2001-2014- 2015, on Gas Rate 3.69% 3.69 4-.99 2.68 1.72 o Diesel Rate 0.59% 6.12 3.98 2.86 1.07 o These growth rates were applied undiscounted from the present to 1995 (POL date) and then discounted at 8 3/8% to the end of a 50-year project life (204-5). The average annual equivalent factor resulting from this future growth is 2.05 (i.e. 2.05 x avg. avoided fuel cost = total avoided cost), which means that the fuel escalation benefit alone is 1.05 times the average avoided fuel cost ($O.04-/kWH), or $0.04-18/kWH. Together the gas generation benefit is $0.0818/kWh. Since diesel back-up generators operate up to 4-0% of the time, rlisolacerl diesel costs and diesel escalation were also considererl. The annual outputs for each of the plants were broken into summer (May through August) and winter (September through April) outputs and it was assumed that the rlies~l generators operate 90% of the total 4-0% of the time rluring the ~ winter months. This yields a breakdown of 90% gas/ 10% diesel for the summer months and 50% gas/50% diesel for the winter months. I)iesel generation costs are typically $0.12/kWh, with average equivalent escalation at l()n~, for -33 - a total diesel benefit Of~.24/kWh. It is highly likely that the line outages in the winter would occur at the same time that low flows, insufficient to turn the turbine, would be occurring. The probability that the flow would exceed the minimum operating discharge was calculated for each month (from Table 3) and then multiplied by the probability that the diesel generators would be operating (50%). The-resulting average probability that the Windy River hydropower plant would be displacing diesel fuel during the winter is 25%, and this percentage was applied to the diesel benefit value of SO.74/kWh, yielding a diesel benefit value for the winter of SO.06/kWh. Due to the typically low Windv River flows in the winter and the low reliability of the transmission line from Homer, diesel generators will continue to play an integral role in supplying power to Seldovia. Construction of a hydropower plant at Windy River would not offset the costs of normal generator maintenance and replacement, and thus no benefits were claimed for extended life or reduced operation and maintenance costs associated with the generators. A benefit for employment was claimed as follows: the benefit is 5()% of the labor costs paid to local laborers; local labor costs are 50% of total labor costs; and total labor costs are 60% of total construction costs. The following is a summary of benefits for each plant size. -34 - Installed Capacity, kW '590 no qno Average Annual Energy, MWh 3,100 3,300 3,7 nO * Annual Usable Energy, MWh 2,945 3,135 ~,')l'i Usable Energy, S'Limmer, MWh 1,590 1,850 2, I In Usable Energy, Winter, MWh 1,355 1,28'i t ,lI.n "i Natural Gas Benefit Summer ($0.0818/kWh) $117,000 $136,000 5 I 'i"i,noo Winter ($0.0818/kWh) 55,000 53,000 57,nnn Diesel Benefit Summer ($0.24/kWh) 38,000 44,000 51,000 Winter ($0.06/kWh) 41,000 39,000 42,00(') Employment Benefit 56,000 59,000 64,f)no Total Benefits $307,000 S331,ono S36 Q ,f)nn * Annual Usable Energy = 95% of Average Annual Energy (assumes '5% line loss) COST ANALYSIS A preliminary cost estimate was derived for each of the oroject sizes based on October 1984 prices. Project features are shown below. Installed Operating Penstock -Upper Penstock -Lower CaEacity Range Diam. t l)iam. t 590 kW 16 to 40 cfs 30 in. 1.4 in. 27 in. 1/4 in. 730 20 to 50 33 1.6 30 1/4 900 24 to 60 36 1.7 33 1/4 The cost estimates included the following items: rockfill bin diversion, precast concrete intake; 1,980 feet of polvethylene pioe; 1,440 feet of steel pipe; powerhouse and associated equipment; tailrace; transmission line; roarl improvements; mobilization; demobilization; contingencies (?f)%); engineering and design (7.5%); supervision and administration (6.5%); operation anrl maintenance, and interest during construction O.n.cJ based on an I ~-month construction period. Costs were amortized over 5f) vears, using an interest Operation and Maintenance Normal operation, maintenance, and repair would he carried out hv local residents, with major machinery repair, etc., being performed bv journeymen who would have to be called in. The installation would be basicallv a remote site, with a relatively simple layout and corresponding low maintenance requirements. A compilation of costs associated with hvdrooower olants in tl)e Pacific Northwest indicate that typical operation and maintenance costs are about 8% of the annual debt for plants under 5 M W. (1) Estimated costs are as follows: Installed First Total Amorti7.ed Total CaEacity Cost I.D.C. Inv. Cost Inv. Costs Annual (:osts* 590 kW $4,884,000 $301,000 $5,185,000 $442,000 $477 ,oon 730 5,157,000 318,000 5,475,000 4(,7,000 '504,000 900 5,562,000 343,000 5,905,000 504,000 544,000 * Total Annual Costs = Ann. Inv. Costs + 8% (0 N. M) (1) Ott Water Engineers -36 - DET AILED COST ESTIMATE (590 kW Plant) ITEM/DESCRIPTION QUANTITY UNIT UNIT PRICE TOTAL MOB. &: DEMOB. L.S. $60,000 sm,oon DIVERSION &: INTAKE Bin Structure 1 L.S. 14,500 14,500 Rockfill 180 C.Y. 65 11,700 Riprap 70 C.Y. 100 7,00n 24-inch C.M.P. 20 L.F. 30 6()(l 24-inch Gate Valve 1 EA. 10,000 10,000 Pre-cast Concrete Manhole EA. 5,000 5,OnO {6-ft. diameter} Concrete Base 2 C.Y. 1,000 2,000 Trashrack 1 EA. 3,000 ~,OOO 30-inch Butterfly Valve 1 EA. 10,000 10,ono Total Diversion &: Intake S63,gOO PENSTOCK 30-inch Polyethylene Pipe 1980 L.F. 500 S990,000 27-inch Steel Pipe 1440 L.F. 720 1,036,gon Anchor Blocks and Thrust Blocks 300 C.Y. 1,000 ~OO,OOO Drain and Vent 1 L.S. 13,000 13,000 Rock Bolts 100 EA. 30 3,000 Rock Excavation 1,000 C.Y. 100 100,00n Total Penstock S2,4lJ.?,gnn POWERHOUSE Structure 1 EA. 140,000 S 140,00n Turbine/Generator 1 EA. 174,000 114,ono Accessory Electric 1 EA. 14?,000 14?,ono Auxiliary Systems &: Equip. 1 EA. 13,000 1 ~,non Switchyard 1 EA. 21,000 ?1,()no Tailrace 1 EA. 36,000 16,000 Total Powerhouse S'in,ono -37 - TRANSMISSION LINE New Transmission Line Transfer Switching Substation Total Transmission Line ROAD IMPROVEMENTS Upgrade Existing Road Repair Bridge Total Road Improvements SUBTOTAL Contingincies (20%) Engineering &. Design (7.5%) QUANTITY 2.5 1 5 1 Supervision &. Administration (6.5%) TOT AL FIRST COST Interest During Construction TOTAL INVESTMENT COST EVALUATION UNIT Miles L.S. Miles EA. UNIT PRIeF 100,000 100,000 70,000 100,000 TOTAL $250,000 100,000 <;350,000 ~l 00,000 10 0,OnO $200,000 729,000 771,000 237,000 301,000 $5,1 g 5,000 Net benefits and benefit-cost ratios were determinerl for each plant size to derive the optimum size, and are as follows: Installed Annual Annual CaEacity Costs Benefits Net Benefits PJ/C Ratio 590 kW $477,000 $307,000 $ -170,000 0.(,4 730 504,000 331,000 -173,000 0.(,6 900 544,000 369,000 -175,000 o.~~ The analysis indicates that none of the project sizes are economicallv feasible, even when considering a relatively inexpensive transmission option. The optimum plant size would be that one which provides maximum net benefits. The above analysis indicates that a plant smaller than 590 kW mav have greater net benefits " I, I I II I' If 11 I, than the three plant sizes investigated, since net benefits increasp with decreasing plant size. The onlv costs which varv with plant size are those associated with the penstock materials and the turbine and generator. The costs of the diversion, intake, penstock installation, powerhouse, transmission line, anrl road improvements would be the same for any size of plant. A verv gradual decline in costs could therefore be expected with decreasing plant sizes. Benefits, on the other hand, would decrease steadily with plant size since less energy would be produced. This leads to a trend towards decreasing benefits for smaller-sized plants. The optimum plant would be that which represents the breakpoint on a plot of plant size versus net benefits, and that would probablv occur at just below 590 kW. Regardless of the exact size representing the optimum size, net benefits would still be negative and the project economicallv infeasible. Based on the findings shown here, the 590 kW plant provides maximum net benefits and is therefore the selected plan, and a breakdown of costs and benefits is provided for that plan. ANNUAL COSTS Investment Cost, incl. IDC Interest and Amortization (50 years at 8-3/8%) Operation and Maintenance Total Annual Cost ANNUAL BENEFITS Displaced Natural Gas Benefit Cost Displaced Diesel Benefit Employment Benefit Total Annual Benefits BENEFIT-COST RATIO NET ANNUAL P>ENEFIT $ 5, I g 5,OOn 442,000 15,000 $lJ.77,Onn S 17?,f)OO 79,000 56,oon S307,onn -<; 17 0,nnn , " II: t :i Il The project would provide a significant amount of power onlv during the warmer months. Throughout most of the vear, supolemental power woulrl he required from other sources. Net benefits calculated are all negative and are based upon henefits which may be overestimated since (l) the energv analvses were based on average monthly flows data; (2) the output of the oroposed Plradlev Lake Hvdronower Project was assumed inadequate to meet the total Kenai Peninsula energv demand throughout the Windy River project life, and (3) future imorovements in the reliability of the line from Homer would invalidate a large portion of the diesel benefits claimed. Under existing Federal evaluation criteria the oroject as designF~d cannot recover costs over a 50-year life and therefore does not aooear economicallv feasible. No further Corps of Engineers studies of hvdronower development at Winnv River are warranted at this time. -40 - :1 II I I' I ,I II II I, 'I i I