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HomeMy WebLinkAboutHydroelectric Powerplant Siting In Glacial Areas of Alaska 1978...... r --I r r i HYD 076 Alaska Energy Authority LIBKARY COPY HYDROELECTRIC POWERPLANT SITING IN GLACIAL AREAS OF ALASKA BY DON L. SHIRA Alaska Power Authority (no date) HYDROELECTRIC POWERPLANT SITING IN GLACIAL AREAS OF ALASKA Donald L. Shira 1/ ABSTRACT Alaska has the largest undeveloped hydroelectric resources of any state in the nation. The problems associated with hydroelectric power- plant siting in glacial areas of Alaska are discussed. A brief history of hydro site investigations is given. The Alaska Power Administration (fl,PA) operates two hydroelectric projects in the State of Alaska, the Eklutna Project located near Anchorage, and the Snettisham Project near Jtneau--both located in glacial fed drainage basins. Operating experi- er,ces gained from these two projects are related to new hydro plant inves tiqations. The unusual nature of hydro sites in Alaska is noted as dre sumL: hydrologic problems encountered during investigations of new sites Hi glacial areas, which include: glacial storage and weather conditions which affect flow duration and energy output; runoff vs. elevation characteristics; and sedimentation. Construction problems associated w.~ th hydroelectric powerplants and related features discussed are: glacial valley geologic characteristics; site accessibility; and trans- mission line locations. Potential environmental effects and impacts of h?droelectric plants are also discussed. All of these factors bear on f·.1ture use of this abundant source of renewable energy. INTRODUCTION Alaska has a long history of hydropower development, dating back to a water-powered sawmill at Sitka in the 1840's. During the early part of this century, dozens of small, water-power projects were built in Alaska tc, provide mechanical and electrical power for mines, fish pro- c ~;inq, sawmills, and towns. Most of the early projects have now been abctndolled, but some are st.ill in operation after more than 60 years ::-ervice. Only a handful of hydroelectric projects have been developed since the t:arly days, mainly because diesel engines and gas turbine powerplants became the easiest and cheapest ways to provide new power supplies where ctr1d wh<c:n needed. Prior to World War II the population and energy re- quirements in the State were small. Power demands began to increase rapidly after the war. In 1956 the total electric utility installed gen- erating capacity was approximately 100 megawatts (MW). Hydro comprised ;)Q% of the generating capacity in 1956 while steam (30%) and diesel (20 ) ,:::omprised the balance. There was no gas turbine generation at that time. In 1976 this had increased ten-fold to nearly 1,000 MW. In 1976 steam t~as 7"'6, diesel 21%, gas turbine 59%, with hydro satisfying only 13% of ~laska's electrical requirements. Although development of Alaska's hydro resources has been slow, \vork has progressed on defining the resources. We now know that Alaska has the lar9est reserves of undeveloped hydroelectric energy of any state of the nation--more than one-third of the U.S. total. ·----,-------~----- if--chief of Planning Division, Alaska Power Administration, Juneau, AK 1 SHIRA Escalating fuel prices, and concern with long-term availability of gas and oil has led to vastly increased interest in new hydro projects. The larger Alaskan hydro resources represent a very attractive option to tte State for expanding the use of renewable resources in Alaska's basic erergy systems. This interest is reflected in active proposals for the urper Susitna Project and a growing list of smaller projects for Alaskan cc,astal cities, from Ketchikan to Kodiak. There is a favorable outlook tt.at hydro will play an important role in meeting Alaska's long-term P<>Wer needs. Most of the current proposals for new hydroelectric projects reflect the influence of glaciers, past and present. This paper focuses on ways g:.aciers and cold weather conditions can influence decisions on hydro pl~ojects. Two hydroelectric projects are operated by Alaska Power Administra- tLon, the Eklutna and Snettisham hydroelectric projects. The experience g;iined and knowledge resulting from thirty years of Alaskan hydro power iwestigations by the Bureau of Reclamation and Alaska Power Administra- t.ion are discussed. The following discussions emphasize some of the conditions in Alaska t·1at influence decisions on powerplant siting. They are by no means all- inclusive. Specific detail is omitted to permit discussion of a broader assortment of factors within the space limitation provided. EXISTING HYDROELECTRIC RESOURCES Developed hydroelectric resources in the State of Alaska are less than one-half of one percent of identified available resources. Current installed hydro capacity is 123,200 kilowatts (kw) which represents about 13 percent of the total installed power generating capacity in the State. f.'.ost hydro power development (78, 200 kw) is in the southeast Alaska Legion. Developments range in size from 400 kw at Skagway to 47,200 kw c:.t the Snettisham Project near Juneau. Remaining hydro power develop- ment in the State (45,000 kw) is in the Southcentral Region with develop- nents at Cooper Lake on the Kenai Peninsula (15,000 kw) and Eklutna 30,000 kw) near Anchorage. POTENTIAL HYDROELECTRIC RESOURCES !Jntil the end of World War II, interest in hydro resources in Alaska "vet~; qcm~rally limited to small hydro plants for timber, mining, fishery, .md l:Ommunity power su[Jplies. Until recently diesel fuel and natural gas ·o~erc considered abundant low-cost fuels. Therefore, interest in deve1of.>- lti<J the hyd.roeh·<..:tric projects for the lanwr powLct ::-;y;;tL•ms wac; :;liqllt. 'ojnC(! tlw OPEC oil embargo and resulting ''sky-rocketinq" oil prices, in,- tcrcst in previously identified hydro sites has been renewed. Alaska's hydroelectric resources have been identified through inV\~fJ­ tigations by government and industry since about 1900. Prior to World War II, extensive work was done in identifying hydro sites in Southeast Alaska, and some others were identified adjacent to the Gulf Coast and in tributaries to Bristol Bay. The Bureau of Reclamation completed the first statewide reconnaissance of Alaska hydro resources in 1948, which included the identification of some of the major hydroelectric potentials. Since that time, project, basin, and inventory studies by private indus- try, Reclamat.ion, Alaska Power Administration, USGS, Corps of Engineers, etc., have resulted in substantial data on the hydro resources. Reclamation and APA completed a statewide inventory in the mid- 1960's. This study consisted of examination of all potential sites 2 SHIRA id<mtified in previous studies, and a careful examination of available US(;s topographic maps in a search for additional sites. Approximately 20UO potential sites were examined in this process. In further studies all but 700 sites were eliminated by obvious physical restraints. The 70') remaining sites were further examined by establishing estimates of po•,Jer potential--preliminary evaluation of runoff and available head and a rough estimate of facilities needed. The list was then reduced to 252 sites by eliminating those for which cost of facilities would obviously ex:eed value of the power potential. Rough project plans were developed for the 252 sites. This work included hydrologic estimates, evaluation of reservoir capacity, and designs and cost estimates for facilities needed. The result was a reasonably consistent, statewide evaluation of (1) the more attractive hydroelectric potentials, (2) the approximate size and type of facilities needed to develop the potentials, and (3) the relative cost of producing tre power. Table l summarizes the list of 76 sites which appeared to have the greatest merit based on economic, engineering, and geologic factors. Figure 1 illustrates these. Energy potential for the 76 sites is esti- m<:.ted at 170 billion kilowatt-hours per year, over one-third the total undeveloped hydroelectric potential of the United States. This summary if: generally accepted as the best available measure of potentially feasi- bj_e hydro power resources in the State. Hydroelectric sites are by no means evenly distributed in the State. There are five significant "World-Class" projects located on major river systems that have a potential for large amounts of relative low-cost power. They are: Upper Susitna, Yukon-Taiya, Wood Canyon, Woodchopper, and Rampart. These five projects represent energy potential of 98 bil- l.i.on kwh/year, or 57% of the inventory total. A few other sites exist n·)rth of the Alaska Range on major river systems. Most of the smaller attractive sites are located in the heavy precipitation areas of South- e.i.st Alaska and some areas adjacent to the Gulf of Alaska. Smaller hydro projects in other areas appear unattractive because of extensive physical w:;rk needed to develop the relatively small amounts of energy. Other than the Upper Susitna River Project, most of the interest in hydro sites has been concentrated in Southeast Alaska and along the Gulf. EFFECTS OF GLACIERS ON POTENTIAL HYDRO RESOURCES Glaciation-General Most desirable smaller-sized hydro projects are located in South- East Alaska and along the Gulf areas which are also the areas most di- tectly influenced by glaciers. This paper concentrates on hydro sites j n these areas. In the past several glacial periods, much of the State was covered by glaciers and ice fields. The Gulf areas and southeast Alaska still 1:etain glaciers to varying degrees. It is estimated that Alaska's pres- E~nt total glacier and ice field area is approximately 11 million acres or J!~ percent of Alaska's total area (see Figure 2). ln Southeast Alaska •Jlaciers and ice fields are widespread and often extensive. There arE~ :1umerous spectacular fjords piercing the mainland. These fjords are former drainage courses that were erroded and deepened by glaciers and ice currents. The perched lakes lying along the fjords offer excellent ~ydro sites with high heads, generally good foundations, and potential for developing substantial storage capacity. 3 SHIRA ~ Ul II: H ~ Canyon) 3. 4 . Kobul< River Strearr: Noatak Noato.k P. Noatal< Kobuk R. ALAS !fA POViEF ADM ~N1;;;, fh.f\:1-.iV:" ·::~1.0\RY .l\LA.'~KA U)YJI:P lPlCED HVI.JRCELECTF.l~' PO'TENTIALS ... ~OC kw-1 continuous power) d.nd larger Averaqe Per- nrainaqr Area Ac. t. i ve Aver ayt .l\.nnua l cent Continuous Sloraoe Head Runoff -----~:3.:..:~~ \ _Ll..'~QE_~_J __ (~ __ (}OO AFJ 12. 700 7. 500 1 3~ 7. 500 1 oc 8. 3 • 2 00 199 5. 600 7,000 4,'!()0 16E 4,500 100 7 • 84 0 (,. 600 114 5. 7 00 100 Power 93 87 INSTALIJITION 1\T 50\ LOAD F 1\CTOR rnS~11ed. const.ru~tion Capac.i ty Cost 6/ 82D Hi6 760 174 613 140 526 L'O ( $/Inst. ---kw) (Rounded to ----~n~ed~~est $100) T~~_suk __ S~'~:3:C~l~t:}~-. ··---:!_~.22_ _____ }_,_~E!Q:~-____ li'!? __ ~-.~~·---l ()(' 60 33 ------~----__€6 --- 800 1,000 '20\- l, 'lOC' 1, 80(' Cross 7. Dulbi 8. Huqhes 9. Kanuti 12. Junction Island 13. Bruskasna 14. Carlo ~ Healy _Jslag1e) 16. Biq Delta 17. Gerstle 18. 19. 21). Johnson Cathedral Bluffs ~rt t'·:)rcupine {Campbell n. Woodchopper 23. Fort)'l!lile 24. Yukon-Ta>ya Yukor. R. 120,000 Koyukuk R. 2>. 700 2L, Koyukuk R. 18,700 y Koyukuk P. 18,000 13,800 Melozitna R. 2,659 l,BOO -Yukon---R-.-----------256,000·---i.T Tanana R. 42,500 29,tl00 Nenana R. 650 840 Nenana R. 1, 190 53 __ _!!,_e_n~:., ________ 1,900 310 Tanana R. 15,300 6, 450 Tanana R. 10,700 _!/ Tanana R. 10,450 5,300 Tanana R~ 8, 550 4, 900 R. Yukon P 122,000 19,000 Fortymi1e R. 6,060 1,610 Yukon R. 25,700 21.000 94 68 49 166 270 72 160,000 19,200 12,300 11,900 1,400 'io9, ooo 100 1,400 122 55 100 184 100 266 B3 96 59 9' 500 --50 149 7. 830 97 105 146 5,800 100 79 445 81,000 100 3. 904 313 9,100 100 265 300 57,600 100 1,620 324 3,230 84 83 1,913 !3,500 100 2,400 2/ ;.ake Iliamna K•ncnak R. 6,440 11, 114 14,600 lOD 12,300 L070 482 1,612 282 6,400 2, )30 840 987 438 920 693 34,200 2,320 14,200 723 21, 000 ? ,800 244 110 368 64 800 1,40C 1,000 1,201' 1,460 ____ _ 532 1,500 (40) (30) 100 210 15!l 5,040 2/ 530 2,160 3./ 166 3,2\10 2,' 1,000 1,600 1,600 1,500 200-400 500 500 800 300 28. :azuni!Jd Tazuuna R. 346 420 393 724 96 26 224 51 29. l"gerso1 (Lackbuna Lake! Kijlk R. 300 472 1,120 695 99 72 630 144 1,300 Lake 33. ChaJ<acha.mna 34. c:offee 37. Ta1achulitna (Shell) 38. Skwentan (Hayes! 39. Lo~er Chulitna 40 . Tok ichi tna Lake fork of Crescent }L Chakachatna R. Beluga R. Skwentna Skwnet.na P.. Chulitna R. ChuJ itna R. 200 1.120 860 840 6,400 2,250 950 2 ,6()0 ~~~56 1:) 306 1,700 1. 2,B.SO S75 860 1/ 2,700 517 793 109 142 82 124 291 89 186 454 2,460 1,800 1,800 12,750 4,500 1,900 6,350 99 20 100 183 18 100 24 79 159 45 6, ?OO ___ ___!i?_,~--~-, 92 179 1,600 160 210 1.390 41 366 37 (75 (98) 900 600 L 100 1,000 1,000 394 90 BOO BOt 184 BOO --------------------- n; t1 ...... (1) ...... {J1 en ::X: H ~ r:::rrau1age Act.t.ve Ax·ea Storage __________ J,~q.nn _. ) __ .Jl.O..QQ.21!J. 1,250 675 42. 43. 44. Whiskers :::.us1 tna. :R. 6, 320 Lane R. Gold 47. vee Susitn."! R. 4,140 1,550 48. Denali Sus1tn• R. 1,260 5,000 49. Snow Sncv,; H. 84.7 354 87.8 372 190 420. ~ 0. Brad ley La!<<:___ ·------B_!"jl3_l_££ Cr . 51. Lowe (Keystone Canyon) Lowe R. 52. Hill ion Dollar Copper R. 24,200 1/ 53. Cleav<' (Peninsula) Cor-:per E. 21,500 l/ 54. WOOd Canyon Copper R. 20,600 21, OoO Average Per- Averaqe Annual cent Head Runoff Regula- 59 7,500 169 7,500 189 7,327 653 89 165 950 ~.310 5/ 535 -- 445 1,400 38,000 28,000 26,700 97 100 190 335 320 870 80 11. o -12 5 2. 248 !n (oo 57. Speel River, Snettisham Speel R~ 194 JJO 273 INSTAU.A'f iON AT 50' LOAD F AC'.I'OR Installed Capacity Const.~:Uction :ontlnuous Fir. CO•t 6/ ($/!nat. -kw) (Rounded to nearest $100) 42 368 84 240 260 (7)8) {478) (386) 1,100 1,100 800 1,300 120 1,052 130 1,139 SOl -----7,000 500 32 47 29 220 410 2,500 {--} 27B 63 1,000 410 94 600 254 58 1·, 100 1. 927 440 1' 400 3,600 820 1,300 21,900 3,600 !I 300 31 275 63 800 58. Tease Cr. 'rease Cr. 11.4 33 1,034 no 75 s 7o 1<. 1,4oo 59. Sweetheart Falls Cr. Sweetheart Fall c. Cr. 1lnn<Uned scenery Cr. 62. 'fhO!IIdS Bay (Cascad<; Cr.) C.,scade "r. &3 Stikine R~ver 64. Goat 67. Leduc 68. Rudyerd 69. Punchbowl Creek Grace 72. swan Lake 73~ Maksoutof Rlver 74. Deer 75. Takat.z. Creek S.itkine R. GoaL Cr. Tyee cr. Ur:named Leduc R. Unnamr-:-d Punc!"tbowl ·:r. Falls Cr Ma.k:soutcf :. ~rnnamed 'T'akatz C.:r. 76. Green L.ake ---------_VE~c!..:"·------------- 35. 2 250 612 250 100 14 125 29 BOO 18 .. 9 72 1,442 160 88 19 166 38 600 • t:,JO 7. 1 13 .• , 26,000 61 61 100 291 45,000 l '130 9,900 2' 260 900 1,056 112 ;~n 10 87 20 1,200 > 241 1,600 (,22 61 63 126 lOC lCH 9~1 9 62 14 83 64 19 15 1,100 800 800 36.4 132 275 336 91 69 15 1.100 23. 7 4 100 67 10. 6 82 29 88 -~~----- 272 114 ·Jt 99J 129 353 212 84 l~ 3.5 ll f. 117 24 800 31 7 900 97 20 1,000 52 11 1,300 1/ Reservoir held essentiaJly full for operation with upstream plants. 2; Based on 75% load factor. 3; Diversior. af Yukon-Taiya flow from Yukon Piver IN()Uld reduce cn:1tinuous power at downstream si t_es, by the following amounts: {1) Woodchopper -38,000 KW, (2) Rampart 610, r\W, 14;1 Ilc~"Ly ::::ro::;s 17.01000 KW, (5) Unevaluated amounts in other reaches of the Yukon River. 4/ Based on 69.4% load factor. S/ Operated as a system. ~/ January 1968 cost base. ~ ..... 11) ..... ....... 0 0 :::l rt 1-'· :::J c: 11) 0.. 0\ (/) :r:: H ~ ,..---~ -- i c1>--'~ -~ -~-T ~:."" -r y--~, I ~~-~ ~ ~ .~ <,... ( YJ'J1-v-~/ -~ K ARCTIC'--~ y ·--,/· \ AU~~ I ~ .,-t_~ .-... ' -- -c: (~ro.,... . "---"--. . f ~':(~ ~7 K.AHUT~I -~' -j ~ ~ ·--y J _;~,~,_. O'OACUPINE '' ~ ~ . ~-\ . \ ~"~,~:.. !IOUTHClHT~Al ~ -~ ,..,. .,, SUBREGIONS i':._ ( ~ _/-,_T :ro '"' ' ., ~·~" 1 'UI<,._~ ' ' ·' -JUNCTIOO< ' -A ·~ -v ~ .... "------~ ';>\ / r--'_ • " ... ~ '<.:..,. •• ., " ' v~ A > -~· , -·•->il~L• 15 ' -"" ' J b~··,,~~• ,Lcr... 'vj .;... .... •-~~ ' s:=.ru·~. ~HAll 's'/1 \ Po--L~-IIIOM~II: ·, ' -c-' _,.-. " -v I TQt( AlliE 43 • KtETHA "" TNA :::~ 0 ;;'a VEE 41 \ " c..,~ • ,J z.~ .... lll -ERS,.. TIIIA _,../' ( l=NTNA Jll '\ , -~I(UJ 7b v UNDEVELOPED HYDROELECTRIC RESOURCES OF ALASKA ~­-~- ">:l "-'· .Q c: to; CD f-.< ..J (/) ::X: H ~ a:r.d Percent of Acres Total !<egip.!]_ Arctic 'NC'\~"':h·wes t Yukon Southwest Southcentra1 Southeast •rotal State (Millions) 0.1 -- '") ~ ~ .. ~'~ 0 0 . ~· :, .• 2.2 10.9 \ , ~;r .;:, Al£UT!AM } -- 21 ~ f 51 ~0 r---~ ~ltc'l'tC OCEAN GULF OF ALASKA 0 50 100150200MolH ~.~~~--~ d ~ r •••• ''•• J~'nt ftt•rat-Stet• Le•d U11 Ph·nnf~tl Co••isslen~19l1 Mtdlllt~ fro• Fatt!lnl, 1911. EXPLANATION um!m Generally continuous permafrost ~ Discontinuous permafrost [~~ Isolated masses of permafrost L_) Generally free of permafrost .... Glaciers ::>cc:Jrrence of Permafrost and General Location of Glaciers in Alaska. "'l '"'· '.Q 1: i'j (!) "" Past glaciation has left a wide variety of geologic conditions that have an effect on plant siting. In some areas glaciers scoured away the unconsolidated material and left solid rock. In other areas glaciers deposited course sediments of a homogenous nature and lacking in fine material. In still other areas there are layers of glacial till, grav- els, etc., all intermixed. Sedimentation In Alaska, as elsewhere, all natural streams transport suspended sediment, although the quantity, size distribution, and physical and chemical nature of the particles vary from time to time and stream to stream. The quantity and nature of stream-borne sediments are influ- enced by the topography, precipitation, temperature, geology, sdil conditions, and vegetative cover. In Alaska, the character and distri- bution of suspended sediments are made even more complex by the contri- bution by glaciers of large amounts of very fine material (glacial flour) to many streams. Knowledge of suspended-sediment discharge in Alaskan streams is limited, restricted to data from a few short-term daily sampling sites on the larger rivers. In general, nonglacial streams transport less than 100 mg/1 of suspended sediment during the summer; in contrast as much as 2,000 mg/1 is carried in streams below actively moving glaciers. Nonglacial streams often transport their highest sediment concentrations during the spring melt or during periods of heavy rainfall, whereas glacial streams transport their highest concentrations during heavy melt- water runoff, usually in middle or late summer. During fall and winter, both glacial and nonglacial streams carry less sediment than in summer. Hydrologic Conditions The Maritime Zone which influences the weather in Southeast Alaska, is characterized by heavy precipitation in the form of rain and snowfall. The coastal area frequently has high variations in climate within a few miles. This is associated with normal orographic processes. Since water sheds for many of the hydroelectric projects are small, the variations become significant in planning projects. As an example, the precipita- tion in downtown Juneau at sea level is approximately 80 inches per year. Seven miles southwest across Douglas Island the annual precipitation is 40 inches. One mile northeast of downtown Juneau at elevation 3300 on Mount Juneau, 200 inches of precipitation is normal. Another example is, snow in the town of Juneau may be melted by rain during the winter, while 30 miles north of town 4 to 5 feet accumula~e. At the same time, 8 feet on the level is normal·at the Snettisham hydroelectric project 26 miles southeast of town. All three places are at sea level. Actual extremes are no doubt higher. Average annual temperatures in Southeast Alaska are in the low 40's at sea level. For each 1000 foot increase in elevation, the temperature decreases approximately 3° F. This creates a situation favorable to forming glaciers. It also introduces marked changes in seasonal runoff patterns. At the lower elevations, runoff comes at nearly the same time and in the s ame amounts as the precipitation because of minimal inter- ference of the freezing process. At the higher elevations the runoff pattern follows the seasonal temperature curve more closely. These factors are significant in sizing storage facilities for hydro projects. Hydrologic characteristics for glacial influenced streams vary greatly from those of non-glacier .affected streams. Typically streams 8 SHIRA in the "lower 48," dependent upon snow pack for runoff, have low flows during the winter, peak flows in the spring due to melting snow pack and rains, with flows dwindling to very low during the hot summer months. Glacial influenced streams react differently. Glaciers store a tremen- dous amount of water in the solid state. Characteristics of glacial run- off include: stream flows primarily influenced by temperature; distinct day to night differences in volume; high silt content of stream water; and occasional outburst floods, all having pronounced effects on Alaskan streams. During warm dry years glaciers release m6re water, maintaining streamflows and surface water in low ground areas. During wet, cold summers glaciers retain water as ice and snow which again stabilizes stream flows and water levels. The mean monthly inflows and temperatures at Eklutna Lake were analyzed to show the relationship runoff has to temperature. Maximum runoff caused by snow and glacier melt is during the warm months of July and August (see Figure 3). Attempts to develop methods of forecasting runoff in glacier-fed streams by trying to develop a relationship between snowpack and runoff have not been successful. Snow-water content and runoff into Eklutna Lake for the period 1963-1974 was analyzed to demonstrate the lack of significant relationship on a year to year basis (see Figure 3). Even though glaciers provide considerable natural storage not inher- ent in non-glacier affected streams, man-made storage is still required. This additional storage is needed because of the cold dominated climate that affects the winter runoff patterns at the time when electric energy demands are the highest. At the Eklutna hydroelectric project less than 20 percent of the average annual runoff occurs during the cold weather months from October through May when energy consumption is higher than average. In an extreme year, less than 14 percent of the annual runoff may occur during these eight months. As an example of the influence of orographic precipitation and the climatic change accompanying increases in elevation, the following is related. During investigations of the Takatz Creek Project, a glacial- influenced potential power source for the city of Sitka in Southeast Alaska, it was found that runoff data was very limited. Correlations were made with other streams in the area that had some records and the Takatz Creek runoff was constructed for a 5 year period. During the cor- relation studies it was found that the streamflow data was strongly in- fluenced by location, orientation and elevation factors on both runoff amounts and distribution. For the Takatz Creek Project approximately 60 percent of the drainage area was above the power development. Baranof Island stream data was used to get flow distribution above Takatz Lake. The unit runoff above Takatz Lake was established using data from several Southeast Alaska areas: Juneau vicinity; Baranof Island; Revillagigedo Island; and Thomas Bay areas. The following Runoff/Precipitation Distri- bution graph was then developed (see Figure 4). E~UTNA AND SNETTISHAM PROJECTS Two examples of hydroelectric projects located in glacial areas are the Eklutna and Snettisham Projects, operated by the Alaska Power Admin- istration. Both projects are located in glacial valleys and rely upon 'I 1.:.1l' i d l runoff for wa tcr supply. Ek lub1c1 Project . t: The Eklutna Creek Valley is a steep sided trough-like glaciated val- ley about 27 miles long with rugged peaks rising sharply up to 8,200 feet. 9 SHIRA lL II "'\ \l) l'r'_ :::1 ~ 4 n" UJ \\.. !. Ul t-- z 4 \11 l Figure 3 14 2.eD :>J I~ I INfLOW 'tC.O ..... !f: I 2 ~I 1 .. 0 ~ I IL vII 2.10 LIJ z ~ 10 v «': t-' '200 v l ... 4 q . 1ao "' t 0 ·.; r-B 1wo g z 0 , v 140 ll! " ~ ul 1'2.0 0 J ~ ~ IL 100 2 l -+ !>O rl. l -0 ~ '-0 0 1 > "' 2 "-40 .... "' 20 ~J rJ 0 61 '-4 6~ G(o w1 6& G'l 0 10 1 I 1t , ,. Y!.A-P.S EKLUTNA F'ROJE.CT WATE.RSHI:.D-<;NOW AND RE.'?E:.RVOIR. INfLOW ~E.LATIQN'5HIP ';.O 40 '30 '20 IO 0 60 / ......--.. ,).J.J. I '\ I ,/' ~-\ I/~ I \ \ I \ 1--------. \ \ -- / I ~ I / \ \ I \ INrl.Jlw rJ 1\ 1\ / / \ \ ---v" '----' -~- JAN P'l~. MA~ Al"f\. M""V'JUNl JUI.Y •"'"· ~tl'r oq. NOV. O&'C.· qo t- .d uJ lL ill 10:, c£ '4 0 60 g ... 3 4".> 0 _, IL z 30 rL 0 ,. I( ,., Ill lfl t.ll ri. 0 MONi~S EKLUTNA P~OJ!:Ci b..ND R~SE:.l'VOII'l. MON11-1LY TE.MPE."A..,.UF\E. INF"L-.OW ~E.LATIONSHIP 10 SHIRA .._.: IL >" IJ.J ....j IJ.J IJ.J (.!) <{ (.!) v IJ.J a: a.. 03 :> IJ.J ....j Figure 4 TAKATZ CREEK PROJECT RU,VOFF and PRECIPITATION DIS1'RJSUTION / 1 Tal!otz L. Outlet __ ~-----/ // IJ.J ~~~~~~-----e~------------~-------o <{ IJ.J a: <{ UJ (.!) <{ 2: / ./ ...-----"'>--/---------'t!!o..••~•Jgt B~---- 4.0ecr L. NOTE: 1-5 Ont4Utlid•~ 6·9onwuhidt of l•lond o Novtmbtr· April • May-Junt Q J11iy-October ' \ SHIRA l I I The typical alpine glacier at the head of Eklutna Creek is about 7 miles long. Its width tapers gradually from about 2 miles at elevation 4,800 to several hundred feet at elevation 1,000. Glacial drift, component of the terraces, forms the natural dam impounding Eklutna Lake. The Eklutna Powerplant is located on glacial sediment deposits of considerable depth and is constructed on a piling foundation. The Eklutna Project. was constructed in the period 1952-1955 to pro- vide power to the Anchorage-Palmer area. Power is developed through the tapping of Eklutna Lake, and by means of a·penstock approximately 24,000 feet long located through Goat Mountain to Knik Arm where the powerplant is located. Eklutna Lake lies at elevation 868 feet above sea level. The Eklutna Powerplant is at sea level and has a total installed capacity of 30,000 kw and averages 143 million kwh of energy annually (see Figure 5) • The original small dam on Eklutna Lake was built in the 1920's. It performed well until the 1964 earthquake when it was damaged to the point that it was determined to be a safety hazard. The old structure was replaced with a new dam that now regulates the top 160,000 acre feet (a.f.) of storage. The quake also caused the precast conduit in the in- take to the power tunnel to separate·allowing large amounts of gravel to enter. Although the powerplant is located on glacial till material, no significant damage occurred to the powerplant itself. A section of the powerhouse shifted vertically about 2 inches, but the generating units remained in-line. The original designs for Eklutna anticipated a sediment accumulation rate for a 50 year period of 10,000 a.f. It was anticipated that most of the heavy sediment would be discharged at the upper end of the lake but that a significant amount of glacial flour would be carried through the lake and the powerplant. The powerplant was therefore designed with stainless steel turbine runners. In the 25 years of operation at Eklutna it was found that the anticipated sediment inflow was overestimated and the amount of material continuing through the lake and plant was less than expected. However, a slight amount of wear has occurred on the main shaft due to the abrasive material accumulating on the packing glands. Snettisham Project The other project operated by the Alaska Power Administration is the Snettisharn Project located approximately 40 miles south of Juneau. The Crater-Long Lake division of the Snettisham Project was authorized in 1962 and construction on the Long Lake division was completed by the corps of Engineers in 1973. The two-phased project has the capacity to supply Juneau's power needs for several years to come. The Crater Lakes division was postponed until such time as power requirements for·the Juneau area indicated the need for construction of that unit. Power is developed by tapping Long Lake with a 9 foot diameter tunnel 8,150 feet to a powerplant at tidewater. The powerplant consists of two turbine generator units having a total installed capacity of 47,200 kilowatts (kw) and capability of an average energy output of about 200 million kilowatt- hours (kwh) per year (see Figure 5). Snettisham power is delivered to Juneau over a 138,000 volt transmission line 40 miles in length of which 2.7 miles are submarine cable. Snettisham is a remote project accessible only by air or water. Movement of personnel, food, fuel, supplies, et~., is all contingent upon weather. Even though Snettisham is a remote camp, recruiting for quali- fied technical personnel has not been a problem. 12 SHIRA ~ DIA. IJATE SfiAH--, (~11015 Figure 5 GOAT MOUNTAIN :·EKLUTNA LAKE : , ~()' DIA SURGE TANK ---- FIXED WHEEL GATE (OPEN)-. INTAKE '·PRECAST CONOUI ~ S• 00341 STRUCTURE STA 27 ,25 • , 9'01A CONCRETE LI NED TUNNEL 23,5!10 Fl LON G_: W"),', KNIK RIVER _,.. ... ' 'fll5 POWERHOUSE·' TAILRACE CONDUIT I I Schematic profile of the Eklutna Project EL .11150 LONG LAKE RESERVOIR ~TER SURfACE RANGE EL 704 TO EL 818 P<>WER TUNNEL 'GLACIER CREEK FAULT ZONE SURGE TANK P ENSTOCK VALVE ROOM EL ·19 POWERHOUSE CH AMQiR Thr. genrrallzed profile above ahowa a rron·st'ctlon of thf' Snt'ttlsham Hydroelectric Project. E 13 . SHIRA At Snettisham, sedimentation was not considered to have significant effects on reservoir storage or plant design. How- ever, as precautionary measures, stain- h ss steel turbine runners were installed as well as a filter system on the cooling water for the packing glands on the main sr.aft.. Wear problems have not been noticeable. The quality of water at Srettisham is excellent, clear, and of U.e proper temperature to support an ar,adromous fish rearing program. Forty- thousand Chum salmon eggs were hatched at Snettisham last year using water directly f1·om the penstock. The hatching success r<:tte was such (85%) that the Alaska Department of Fish and Game decided to e}:pand their facilities and rear 1 mil- l:i.on Chum and King salmon eggs this year w:.th eventual hatching and rearing capac- i'.:y of 56 million fish per year. Experience from constructing and operating the Eklutna Project and partic- ularly the Snettisham Project is extrem- ely valuable in making decisions on l<)cat:ing hydroelectric projects in other a::cas of Alaska. Although Snettisham has h~en operating since 1973, problems asso- ciated with maintaining the transmission line have prevented the project from c:>ming up to its full benefit. Extreme w;;ather conditions and remoteness of f~cilities were major factors. The Snettisham Project has demon- strated that careful designs and loca- tions of transmission lines are extremely important in Alaska. The higher eleva- tions need to be avoided, if at all pos- sible. Problems of deep snow accumula- tion, avalanche problems, snow creep, ice accumulations, and high winds are more r-revalent at higher elevations than lower. If the above problems are carefully con- ~idered and planned for, transmission lines can be located in Alaska to give a minimal amount of outages. A cronological listing of the diffi- culties and problems encountered on the ~.nettisham transmission line since 1972 follows. The photographs show effects of 1m ow creep, avalanche, heavy icing, and high winds on the transmission line (see Figure 6) • 14 , c • • ... 1111 ... E .. "( SHIRA -0 Q) ·-0 .... 0.. E as .c: U) --Q) c:: Cl) -0 ~ 0 -Q) .lit. ~ Q) > -0 CD a. ., ... l. Figure 6 Temporary poles broken by snow creep on Salisbury Ridge. 15 Heavy icing and winds ex- ceeding 200 mph caused the collapse of this tower on Salisbury Ridge. Ice built up on tower members 6-7 inches and about 3 inches of rime ice on conductors. Ice buildup on tower mem- bers broke off and fell on bracing, bending members. Avalanche toppled this tower. SHIRA Summer 1972 Winter 1972-73 Summer 1973 Fall 1973 December 1, 1973 January 1974 February 14, 1974 March 1974 Sununer 1974 September 27, 1974 November 1974 December 25, 1974 December 25, 1974- February 1975 February 1, 1975 Sununer 1975 Sununer 1975- Spring 1976 April 7, 1976 April 27, 1976 May 1976 June 15, 1976- June 18, 1976 Sununer 1976 September 20, 1976 September 1976- November 1977 SNETTISHAM TRANSMISSION PROBLEMS Salisbury Ridge section of line constructed. Three towers on the ridge seriously damaged by wind. Corps of Engineers repairs Salisbury Ridge part of line. Construction of transmission line completed. Snettisham goes on line. Minor transmission outages occur. Three towers on Salisbury Ridge collapse. Plans initiated to temporarily repair and then relocate the Salisbury Ridge portion of line. Corps makes temporary repairs on critical section of line. Snettisham goes back on line. New series of outages begins with onset of winter storms. Minor hardware failure on line causes outage. Wind and low clouds prevent repair crew from reach- ing line. Line repaired. Snettisham back on line. Some hardware in Salisbury Ridge section of line replaced. Tower by tower inspection made by APA and Corps of Engineers. Bolts on towers tight- ened, defective hardware replaced, adjustments made to guy wires. Snettisham provides essentially uninterrupted service. Avalanche topples tower 5 miles from powerplant. Tower repairs done and Snettisham back on line. Three wood poles on Salisbury Ridge damaged by snow creep. Transmission outage occurs as a result of snow creep damage. Work begins on Salisbury Ridge line relocation. Also studies initiated on ways to mitigate avalanche danger to transmission towers. Relocation of Salisbury Ridge section of transmis- sion line completed. Mild 1976-1977 winter resulted in no operating problems. Winds in excess of 100 mph and heavy snowfall experienced in November 1977--no operating problems. ENVIRONMENTAL EFFECTS There is very real potential for environmental impacts from the development of hydroelectric plants and related facilities. The hydro sites offer a wide range of impacts. Some have little significance, while others present major change or loss. Principal environmental impacts re- late to fish and wildlife, including their habitat; water quantity and quality; downstream effects in terms of sedimentation, nutrients, and stream bank erosion; and visual impacts. In addition, there is potential for social impacts, particularly related to the life-style of small, re- mote Alaska c~unities in close proximity to major project developments. It appears that a number of smaller projects, especially in South- 16 SHIRA east Alaska, can be developed with a ~n~mum of environmental impact. Aside from the fish and wildlife concerns, probably the most significant environmental problems associated with developing hydro projects have to do with the visual impacts of transmission lines. Environmentally it is preferable that transmission lines be placed underwater or underground to remove them from sight. However, in most cases, if overhead trans- mission lines are precluded, the entire project will be precluded. In most areas of Southeast Alaska it is possible to locate transmission lines close to the water to minimize visual impacts. In some other areas it is difficult to locate transmission lines to reduce the visual impacts due to climate, topographic, and geologic limitations. If a line is located at higher elevations, problems may be experienced such as deep snow, avalanche, high winds, and icing. At Snettisham, for example, the following environmental measures were taken: 1. The underground powerplant was designed to eliminate some of the above-ground visual impacts. 2. The transmission line was located, where possible, low on ridge sides to reduce visual impacts of the line. The towers were painted light green and gray to blend into the natural surrounding landscape. No roads were constructed along the transmission right-of-way, and as a result there has been limited public access. To many people of the nation, Alaska is the last stronghold of un- touched land and natural resources. It is important that planning and decisions having to do with hydro site developments fully recognize the environmental consequences. In addition to complying with existing law, there is a moral responsibility for preserving Alaska's natural beauty. ALASKA COST FACTOR Problems having an effect on construction also affect costs. When estimating project costs in Alaska, an "Alaska Factor" is often computed to determine the construction cost multiplier for adjusting "South 48" prices. Factors contributing to the higher construction cost in Alaska are remoteness, accessibility, and short season for construction. Southeast Alaska is no exception. Travel is mainly by "Alaska taxi" (airplane) or by water, which is often limited by weather. Most Alaska construction sites are remote and require board and room be furnished for workers. currently this adds about $80 per man day cost or $8 to $10 per hour. The general practice of working overtime during the long summer days for the short summer season also adds to the cost of construction in Alaska. For instance transmission line linemen wages average $5 per hour higher because of the overtime pay for a 60 hour week instead of the traditional 40 hour week in the "South 48." Longer working hours, even with the additional costs for overtime, are justified in shortening the time required to complete the job. The cost factor for labor in transmission line construction increases to 2.5 times "South 48" costs when costs are added for transportation of importing people to supplement Alaska labor, extra cost for working under helicopters, and loss of efficiency due to long days and rougher working conditions. 17 SHIRA THE FUTURE FOR HYDRO PCMER DEVELOPMENT IN ALASKA The longer-term role of hydro for Alaska is very much in doubt. txisting studies indicate that long range power needs for most of the State could be met using hydro projects that are basically sound from environmental and economic viewpoints. These longer-term options could be essentially precluded by existing proposals for new National Parks, Refuges, and Wild and Scenic Rivers in Alaska. There is considerable controversy underway within the State and in Congress over "D-2" legislation (Sect. 17 D-2 of the Alaska Native Claims Settlement Act, P.L. 9'2-203). H.R. 39 (the Udall Bill) is pre- sently under. consideration by Congress. APA prepared an analysis of the potential 'impacts of this legislation on the hydro resources in the State and concluded that approximately 93 percent of the sites would be precluded. The desire for non-development in Alaska is nothing new. For years many groups have wanted to preserve Alaska and limit any kind of develop- ment. On the other hand, there are those who pursue development. This is evident in the controversies that have surrounded mining and timber industries. The desire for non-development is being expressed with regard to potential power developments. Conservation groups and others look at power development as "growth-contributing" and claim projected power demands (approximately 12\/year) for the State are over estimated. The State of Alaska has based its economic foundation on the devel- opment of its natural resources, now primarily oil and gas. Exportation of these resources is vital to the national economy. Even if decisions are made now to begin developing the coal and hydro resources of Alaska it will be another decade before any significant turnaround in use of oil and gas can be realized. It, therefore, is extremely important that new energy developments, including hydro power projects, fully consider the economic, environmental, and social impacts to provide the decision maker a full array of the consequences of alternative decisions on future energy options. . 18 SHIRA .