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HomeMy WebLinkAboutAPA1918t j .. " I'"' . ' II.. ,..J J. J' I J I ' ' ~ . L .·l ..... rnJ&iru~& c ~riD&@©@ Susitna Joint Ventvre Document Number I 9/8 Please Return To DOCUMENT CONTROL SUSITNA HYDROELECTRIC PROJECT I .. ~ .. ' . 1. SUM~ARY OF ~~ASKA POWER AUTHORITY DESIGN REFINEtvlENTS TO FEDERAL ENERGY REGULATORY CQgMISSlON LICENSE APPLICATIOI-~ Introduction This report describes proposed design refinements to the Susitna Hydroelectric Project License Application filed by the Alaska Power l-\uthori ty (Power Authority) in FebruRry, 1983, which have been developed by the Power Authority as a result of recently conducted geotechnical investigationso 1.1 vlatana Darn Design Refinements The proposed design refinements for watana Dam are as follows: 1. 2. 3. 4 .. 5 .. 6. 7. 8" Reduced bedrock and alluvium excavation treatment for the dam errillankment foundation. Revised configuration and compcsition of the dam and the cofferdams' inte~·nal zoning. Revised vertical setting and size of diversion tunnels and increased cofferdam height. P.elocation and Ieorientation of the transformer gallery, pov:erhouse and surge chamber caverns. Fev! ... sed a.rrangernent of po~.;er conduits and power intake. Increase in size of main servicB spillway to pass the Probable Maximum Flood (PMF) and elimination of the emergency (fuse-plug type) spillway • Revised layout of approach channels to the power intake and spillway. Construction facilities reduced in accord~nce with reductions in construction work. - r t 1 .l~.; ~: ~ ~r J .. . ~·"·'""-Jit...~4--"--" 0 . . Rotational speed of turbine-generato:r. units increased from 225 to 257Ql rpm~ 10 .. Underground SF6 gas-insulated switchgear and SF6 gas-insulated bus to the ground surface selected instead of an open-air switchyard supplied by oil-filled main leads from the underground power- house. 11. Selection of open-cut trench instead of tunnel for spillway chute drainage. 1.1.,1 Excavation and F'oundo.tion Treatment for Du.m The main dam foundation treatment, as refined, would reduce rock excavation beneath the core and shells and limit excavation of the river valley alluvium to the central 80% of the dam foundation. The areas of the dam in proximity to the upstream and d•.:>wnstream toes of the embankment are now planned to be founded on the riverbed alluvium, with the central 80% to have a bedrock foundation. The 1983 Wi1..ter Geologic Explorations have shown that the bedrQck is of a better quality than originally anticipated. Therefore, only limited excavation of bedrock beneath the embankment is foreseen in the river channel. Fresh hard diorite in most instances exists from the bedrock surface. Removal or foundation treatment (dental excavation of concrete backfill) will be performed in local areas beneath the shells where erodible or otherwise unsatisfactory foundation bedrock is encountered. The quantity of rock to be removed under the enmankment will be reduced from that estimated in the License Application by about :3.75 million cubic yards. The License Application cost estimates ~ssumed a trench beneath the impervious core and filters averaging 40 feet deep, and an average excavated depth under the shells of 10 feet. The design refinement provides a core trench 10 feet deep in the river section, and 20 feet deep on the abut- mentso Excavation under the shells on the abutments averages one foot. A reduction in the tu+al length of grout gallaries, grout drilling, and grouting was also made in view of the better quality foundation bedrock. 2. - I I J I I f I • I i"' ... _ -, ( l -Q., ... , 1.1.2 Darn and Cofferdam Conficruration and Composition The License Application design for the dam cross section has been essentially retained as it is con- sidered to be satisfactory and will prcdnce a stable structure~ To increase safety against se~smic shaking, the steepening of the exterior slopes near the e~tiliank­ ment crest has been eliminated. This results in the same exterior slope from crest to toe both upstream and downstream. The embankment internal zoning design has also been modified to incorporate materials from the required excavations along with by-product materials from the processing operations. The refined layout includes the use of rock and processed granular materi- als in the shells outside the im~~rvious core. This section increases the utilization of available materi- als and will reduce required b)rrow as well as reduce spoil requirements. The cofferdam sections were revised to a more conserva- tive design and a positive slurry trench cutoff to bedrock would be provided. 1.1.3 Vertical Setting and Size of Diversion 'I'~nnels and Cofferdam Heights The two diversion ttinrielz as shown in the License Application were 38 foot diameter concrete lined. The total discharge capacity is 80,500 cfs. One tunnel has an intake portal invert below the riverbed level, while the other is 70 feet higher. With the deep alluvium in the riverbed upstream, ·the low tunnel could result in sediment deposition during flood recession. This tunnel could be partially filled with gravel the.reby reducing its hydraulic capacity for the next flood season@ Therefore, the refinement consists of raising the intake portal invert of the lower tunnel to El. 1445. The refinements also consist of adjusting the location and orientatio~ of the tunnels based on more recent geological information and lowering the upper tunnel for greater hydraulic efficiency which permits decreasing the diameters of both tunnels to 36 feet. The cofferdam locations would simultaneously be ad- justed to utilize the reduced excavation of alluvium in the dam foundation. The length of the upstream cof- ferdam would be reduced by relocating it further downstream.. The freeboard of the cofferdam was in- creased to provide additional safety against ice pileup or higher water levels caused by ice jams. 3. -- I l ! L ( I l J I f f ' ' I l I l ·~ t; / A comparison of the refined design with the License Application follows: License Refined Application Design Tunnel 1 U/S Invert El. 1490 1468 Tunnel "' D/S Invert El. 1450 1455 .l. Tunnel 2 U/S Invert El. 1420 1445 Tunnel 2 D/S Invert El. 1405 1430 U/S Ice-Free Water Level El .. 1535 1532 U/S C~fferdam Crest El. 1545 1550 U/S Cofferdam Freeboard (ft.) 10 18 D/S Ice-free Water Level El. 1468 1468 D/S Cofferdam Crest El. 1472 1495 D/S Cofferdam Freeboard (ft.) 4 27 l.lo4 Relocation and R~0rientation of Caverns 1.1.5 A review of the site geology indicated a major set of fractures which trended N 50°W and a second minor set perpendicular to these. The caverns for the powerhouse, transformer gallery, and surge cha1uber, as shown in the License Application, trend in a direction appro~imately N 20~w, strad0lin§ b€tween the m~jor joint system and a subjoint system. Excavation of the longitudinal walls would be improved if the major joint planes were to intersect the walls as near to the perpendicular as possible. Consequent- ly, the caverns were rotated accordingly. This change will result in less over break of rock in the cavern faces, lessen construction problems and contribute to greate~ safety durinq constructio~. This change was also beneficial to the changes in the water conduit and access tunnel geometry described below. Power Conduits and Intake The License Application indicates a single strt·'::ture power intake with six int~ke passages located approxi- mately 1 000 feet upstream from the dam axis .. The power co~duits consist of six individual penstocks, tunnel and shafts with a developed length of about 1,500 feet each connecting the intake structure to the powerhouse, and two trailrace tunnels approximately 2,000 feet long connecting the powerhouse to the river. The downstream 300 feet of one of the trailrace tunnels utilized the downstream portions of one of the diver- sion tunnels. 4. - "" . J" ~ .J· I I I I " I I I I I f l J / . I \ l .... ""· To reduce the power conduit length in the design refinement, the intake structure was shifted to a location between the spillway ana the river channel and nearer to the dam axis resulting in relocation and shortening of the power conduits. The n~mber of penstock tunnels was reduced from six to three, each of which bifurcates t.o smaller penstock tunnels at a point approximately 200 feet upstream from the powerhouseA Guard valves will be provided for each turbine. The net head on the \.. ~ erating units will be greater 1 and the shorter, more c ficient power conduits wi~l provide better unit operation. Overall, the three power tunnel design will be more cos+_ effective than the six penstock tunnel design. Vertical shafts are also recommended instead of sloping shafts because e~cavation and concretivg of vertical shaftF requires less time, personnel, and equipment, and gi.ven the geologic condi~ions, should result in less over break~ 1. 1. 6 ~~J?illwaxs The License Application shows provisions for dual spillways. In this concept, the service spillway, the outlet works, and two genera~i:.ing units would discharge flows corresponding to floods ,,.;ith 1:10, OOC year occurrence probasili~y (Exhibit EF pp~ E-2-107 4.1.3, (a), (iii})~ For larger floods, the reservoir would be surcharged to a maximum of El. 2201, during the PMF event. Prior to reaching that r~~servoir level the fuse-plug would begin to be brea~~hed and after a period of time, would be fully eroded. The service spillway and fuse-plug emergency spillway would then reach their peak discharge of 152,000 cfs and 120,000 cfs, respectively. This spillway concept would allow passing of the PMF without overtopping the darn~ During the PMF, the minimum reservoir freeboard would be 4 feet. An alternative spillway arrangement of a gated, single spillway has been studied, sized for the PMF with cri t.eria of maintaining the same freeboard as the dual spillway scheme and the same safety against dam overtopping. Although this review process was initiated to seek lower costs, elimination of the fuse-plug was considered a be:tJefi t environmentally, aestheticallyr and, to some extent, to dru~ safety. Questions had been raised by FERC in their request for supplemental information of April 12, 1983 (See Corrunent No. 2 regarding Exhibit F, at p. 34) as to the safety of the fuse plug against adverse conditions of freezing weather. While the response to the comment indicated 5. .f I f I I I i f I <. ···' I ( . .. tha~ the design could be arra~~ed with proper selaction of granular materials to erode under freez~ng con- ditions successfully and thereby provide the desired flood release, elimination of the fuse-plug structure would eliminate all risk of the fuse-plug not opE::rating. Inasmuch as a gated spillway is required in both the single and dual spillway concepts, and the reliability of a give.n gate design is not materially affected by its size, the larger single spillway design,. absent the fuse-plug, has equivalent or slightly enhanced safety over the dual spillway design in the License Applica- tion. A more tangible benefit of the single spillway design over the dual spillway design included in the License Application is its lower cost for the same total design capacity. Moreover, the analyses led the Powar Authority to conclude that a single spillway design had certain environmental advantages in addition to being as safe and as effective as the dual spillway design. Environ- mental advantageP to the single spillway scheme are as follows: a) Visual iutpact of the projest WGula be red~ced by eliminRting the fuse-plug spillway. Because of the significant extent of the cut for this water passage, its elimination could be considered a major improvement in project aesthetics. b) c) The overall ground surface area& that would be disturbed by construction would be reduced. Construction of the License Application main service spillway would entail disturbing approximately 13 acres, and construction of the emergency spillway would entail disturbing 55 acres, resulting in disruption to a total of 68 acres for the dual spillwa.y scheme. The single spillway design would require disturbance of approximately 22 acres, thus resulting in a net reduction of 46 acres of ground surface to be disturbed by construction. · With either the single or dual spillway scheme, the main service spillway would be operated only for floods greater than the 1:50 year occurrence. For smaller floods, spill discharges in excess of power flows would be made with the fixed cone valves. Thus, there would be no difference .:i.n 6. I I f I l f .... environmental consequences for either the single or dual spillway design for such flows. d) For flows bet'!freen the :,'.~50 and 1:10,000 ye-. J.' flood flow, onl~{ the gated service spillway woul~!;· be operated with the dual spillway scheme (the fuse- plug would remain intact) • Service spillway operation for the dual spillway scheme in ~his flo\v range would have environmental effects substantially equal to the larger gated service spillway being proposed in the single spillway scheme. This statement can be amplified as follows: FACTOR ESTI~~TED EFFECT OF SERVICE SPILLWAY OPERATION S~~LL SPILLWAY LARGE SPILLWAY (For any given flow in the range considered) (License Application) (Proposed Refinement) 1. Operating Head 2. Height of spillw?.~ bucket exit abov~ tail water 3. bpproximate width o~ spillway chutes exit 4. Chute exit velocity 5. Flow energy con- centration (Energy per unit width of chute requiring dissipation) 6. Plunge depth 7. Gas supersaturation Same Same 80 Feet , Reference Value Reference Reference Value Reference Same Same 120 Feet. Same or slightly less because of increased air and skin friction d .. -ag Lower by approximately 33% Same or slightly less because of lower unit energy in the impact area Same or slightly less 7. I I I l 8. Riverbed erosion Reference Same or slightly less 9. Riverbank erosion Same Same ej While it can be argued that the absolute differ- ences of the factors cited above mav be infini-.. tesirnal in those cases which are presented as "slightly less," it is the intent of the above presentation to show, at the least, environmental equivalence between the two schemes in the flow range considered. For both spillway schemes and for any given flood flow between th~ 1:50 year up to the 1:10,000 year event, all flows higher than the hydraulic capacity of the turbines and the cone valves will be passed over the service spillway with resultant erosion and gas supersaturation effects. While logic clearly dictates that these effects will necessarily be less for the large spillway, the differences cannot be quantified in any meaningful way using existing state-of-the-art analyses. For floodd of the 1:10,000 yaar or ·reater recur- rence interval, 'the. proposed larger :.:ervice SPillwav would eliminate se~cTere z:rosi on of about 60 acres which would be associated witn operation of the fuse-plug spillway as described in the License Application~ However, a 1:10,000 year or greater event which differentially impacts only 60 acres is not within a reasonable range of importance Jr~o be seriously considered from an environmental point of view. Thus, a single spillway with the capacity to pass the PMF while maintaining the same reservoir surcharge criterion is recommended. The design refinement also recommends use of radial gates instead of vertical lift gates as shown in the License Application. A radial gate installation would cost less than a vertical gate inst~llation and is the usual choice for operation under subfreezing conditionso 1.1.7 Power Intake and Spillway Approa~h Channels The hydraulic conditions of the approach channels to the power intake and spillway as shown in the License Application can be improved with the relocation of the powerhouse and the power conduits. In the License 8. I I I I I f I J" -...... f I ' .; ..... Application, the power intake is located such that it appears to impede flow to the spillway.. The aesign refinement location of the power intake will eliminate this effect. The approach channels as refined will require larger quantities of rock excavation; however, this materi~l can be used to fill in the dam and for concrete aggregate. 1.1.8 Construction Facilities The lower construction quantities will reduce labor requirements thereby reducing the size of the construc- tion camp and catering services. 1.1.9 Turbine-Generator Unit Speed The design refinement consists of increasing the synchronous speed of the turbine-generator units from 225 rpm as shown in the License Application to 257.1 rpm. Basically, a higher speed unit requires a deeper setting of the turbine distributor below tailwater. The depth shown in the License Application is, however, lower than necessary for t"'Ae 225 rpm turbine and is also sufficient foL the 257~1 rrrn t~rbine. This increase in speed will reduce the physical size and cost of the turbine-generator s~t and also may possibly result in some reduction in the powerhouse size at the time the final design is made. 1.1.10 Gas Insulated Switchgear and Bus· Revisions of the high voltage conductors from the main power transformers to the ground surface and elimina- tion of the ground level switchyard by use of SF6 gas insulated s\vi tchgear and bus are proposed in the design refinement. These revisions include use of a single 9' -0" diameter vertical SF€ bus shaft instead of tv1o vertical 7' -6" diameter cable shafts from the trans- former gallery to the surface. All switching equipment will be underground thus simplifying maintenance. This refinement will provide an improved environment for operation and maintenance by elimination of the poten- tial for icing of eq4ipment in ground level switch- board. Substitution of SF6 buses for oil-filled cables will improve safety by removal of fire hazards .from the cable shaft area. Elimination of the switchyard will also reduce environmental impact and improve aesthetics by the construction of fewer and smaller surface structures. 9. ' \ - .. . J I I I I I i I lcl.ll Spillway Chute Drainag~ Drainage of the spillway chute as sho\v!l ; n the Licens:e Application Qonsists of a drainage tunnel excavated.30 feet below the chute ~lab under the longitudinal centerline of the chute. Angled drainage holes would lead from box drains under the chute slab to the drainage tunnel. The design refinement consists of substituting for the drainage tunnel a gallery exca- vated in an-o~en c~f trench-also along the longitudinal centerline of the chute. Box drains would then lead to this gallery. This refinement simplifies the· cons- truction procedure from that of a tunnelling operation to open cut excavation. 1.2 Devil Capyon Development Design Refinement The design refinement proposed =or Devil Canyon De- velopment consists of increasing the main service spillway capacity to pass the PY'JF 1 thereby allow·ing elimination of the fu§e=plug t.ype emergency spi]_l't"Jay shown in the License Application. This refinement provide.s the following listed advan- tages to which the discussion provided under 1.1.6 for the same Watana development feature also applies: a) b) c) The larger single spillway will be less costly than the dua.J. apillways. Eliminating the fuse-plug type emergency spillway will reduce visual impact and improve aesthetics. The net ground surfdce areas to be disturbed by construction can be raduced. Construction of the License Application service and emergency spill- ways are approximately 12 and 15 acres, respec- tively for a total of 27 acres, The enlarged single spillway would require disturbance of approximately 15 acres resulting in a reduction by 12 acres of ground surface disturbance. d) No net differential environmental impacts due to operation of the spill,way wil.l result for flows up to the 1:10,000 year flood, as previously described for Watana. e) The wider gates 1 ehute and flip bucket will pass the frequent floods with lP.ss intensity of dis- charge. 10. - . . -. ,"-~ ;> -I _/. ' • " • ~ ~---0 "' "'"' ~ ~ .... -~~--~ i I ft f' - '•._ --~ .,._ l'.-:11 ~--:J!II'.IIJII BEFORE THE FEDERAL EN~RGY REGULATORY COMMISSION APPLICATION FOR LICENSE FOR MAJOR PROJECT SUSITNA HYDROELECTRIC PROJECT (Project No~ 7114-000) Ls . ~·t~.~ .. ~,j<~>>F>•7 ·:.__h~ . ----~. -------~~ ' ! ~----····-----~__... --~-,.---~ I• :!mill .~ : t I ~ Revised ~ Exhibit D Tables August, 1984 ' .. -~-..---··- ;,.,i.,:Ci:,_,;' . . . ilW I JDIJI' -, .. _} I~ J 1 / ~ -~.-:~ -....c.._ 1 ! ~ ; r ..... I 41 ~ • • +-+ .. ~~-_;. ' .,.. '0 ,. • • . ' . b ' "'-,.,;:~ ~~ .... Jt.~ ' ... ..,_ -·~ ~>-~ ~ ...... -' _;_. -~< .-F .......,.: _____ , . ....,. .. ·~ ' _..,_. _ ___i -.,...,..,..... ·-· ~_J ._....., ~ ""+ _,_,__j '"""""'"""-1 ·-"'--'•_..._1 ~--~ ~~ "~ EXHIBIT D SUMMARY OF COST ESTIMATE (Prepared by Harza-Ebasco -August 1984) ALL COSTS ARE AT JANUARY 1982 PRICE LEVEL "iW.U!I!! -·-~....Jil!. AND TRANSMISSION PLANT COSTS ARE AS ESTIMATED BY ACRES ~ '"'lUUIII!!!III 1.=.!'111! ·--·-~~-.. , ... -.~ :~·_...-. . ~ , l!YJI' ,.. ..... .. ._ ~\, ·_) ., • llr "' ... ~ ... L__. ~---~----~~---,--.-~~-----,, ·--yr-:-r~~; •= ..... ·'"' ,.,.....,_,.~ .... _,..·-••• "~"--IIJ!I'iH 4.IJ4i!ii&$UUN4.4 lii4#1Sf8llliil~ .\ -' ~iJt-~ • ' ; l; :.r .... L "'' . ' " o I "'· .. -" ..., A ., I. .. --r--,·~~ .,...,..-""""'""" -~ CATEGORY ~-~ ,..,_ ___ ---~ '· . . Production Plant ~ ~ -•• __ ,J Transmission Plant General Plant Indirect Total Construction Overhead Construction TOTAL PROJECT ~ . . 'IIII!!MI!i ........ r~•' ) 4~ J!!lllllll ;..;;::··31111 \.c.iiAI -~~ ~~ ~~ ~ ·~" __ .! ... ~ -.-~J -~..., ~--~----~J -~ ,-r-----J ~ ~ "l11111!11!1!1!! -. ,_,_) '-· ~ c•---~ 0,_ -~_....) REVISED TABLE D.1: SUMMARY OF COST ESTIMATE JANUARY 1982 DOLLARS $ X 10 6 I WATANA DEVIL CANYON TOTAL $2,053 $ 983 $3,036 456 105 561 ......... 6 6 12 . ,...__) 379 171 550 . - $2,894 $1,265 $4,159 467 204 671 -- $3,361 $1,469 $4,830 'il 'I ~ ..... ' u. . -~-----~--.-~---~ --· -"""""'"··~··--•• ... • .... ••-••• ~'· ":\\""' """"-~"-<''"'· t41FLW...,,...,..~~'1111Pl1MW.O!MARII~ ~c;! I ; ,.J ··~ ' ~ J i . l ,;,,..,_, Av·~ t ,._ ' i L.. ~~~ ......... ,~ ~-~~ . '• \. I 0 . r ' • • ·~· /. ' .. ~ ~-.._., ~~· -~~ ~---~ ~ ""~ '-'· L..,, _____ , .._ ..... -··" ~~ ........ _J ...,_ __ j ---"1 .. -......J ·-..•.. -;..] '""'::j ·~ >o-~ ~ ,.,...,..J..t.< REVISED TABLE D.2: ESTIMATE SUMMARY -WATANA ' ' " JANUARY 1982 PRICE LEVEL Line Number Description Amoun~ ( X 10 ) 330 Land & Land Rights •••••••••••••••••••• $ 51 331 Powerplant Structures & Improvements •• 70 332 Reservoir, Dams & Wnterways ••••••••••• 1,351 333 Waterwheels, Turbines & Generators •••• 71 334 Accessory Electrical Equipment •••••••• 21 335 Miscellaneous Powerplant Equipment (Mechanical) ........................ . 1{ 336 Roads, & Railroads .................... ., • 214 Subtotal .............................. . $1,792 Contingency ••••••••••••••••••••••••••• 261 TOTAL PRODUCTION PLANT ................ ~ Totalg ( X 10 ) $2,053 ~~ . . ~ ~""-" -·· :~.1 ~~ t!!il I ~~ ' . Remarks ....... ·._) 'l .. ..,.,..;.>i; Sheet 1 of 5 ----""·:·-~:~-.----..... ~~~-:..._..---~ ...... ____,_ ·---......,.-~ ,.,........,..,,.....,..~~ •· ,..,,..,..,_.._,,,._.,UII,l\11!£4 -IIIIII!J .• IIll'!!£41 Jill .. f.!~~ ;' ·- ' PEVISED TABI,E D. 2 (Cont' d) l ..... ·~~·-::-·e.-, ~·-~ ~~ .-....,.~~ --~ -~ --i _ _, • ~ -~ Line Number Description TOTAL BROUGHT FORWARD •••••••••••e•s•••••••••••• TAANSMISICN PI/i.NT 350 land & I..al1<i Right ••••••• 0 • v ••••• 0 • C) ••••••• •_. ••• " 352 Substation & ~vitching Station Structures & Improvements ••••••••••••••••••••••••••••• l 353 SUbstation & Switching Station Equiprent ., ..... . 354 Steel ~rs & Fixtures ........................ . ... 356 Overhead Conductors & Devices •••••••••••••••••• I 359 I Roads & Trails • • • • • • • • • • • • • • • • • • • • ~ • • • • • • • • • 0 • • Su})IDtal • • • • • e • • e • • • • e • • • • • ., • • • a • • • • • • • • • • • • • • • Contingency •••••••••••••••••••••••••••••••••••• 'IDrAL TRANSMISSr,::N PIANT ' .......... •.• ......... . .. J ·---~--L:"l ~-c-~---~---~---~~ ~ ' • -•~-,..,, ,m • ,.,.....,., ""1''9'7~ -------··· __ ,j -~ JHJ Pm:>un~ ( X 10 ) $ 8 12 131 131 100 $ 395 61 ~ ~~ Total5 ( X 10 ) $ 2,053 $ 456 $ 2,509 ::sz:!l ~ ~,--:. ~-"~~~ Remarks I I ~c~--,, \_, .. t._.~.; . flllilimBI!II ' ===· Sheet 2 of 5 " I ~ ~-.. ·._) • J -to'* ........ ·t' ~~: ';_X ,, t -.3.,.,,.,~;;._.~ I I --~·--~ ~--... ~ Line Number 389 390 391 392 393 3'94 395 396 397 398 399 4-~; "~~ ~ .,..~ --,._ ---~ ._ Description ~ · Ari~:mn·r .. ..~ ( X 10 ) TCJrAL BR(){X;J-fl' FORWARD . . . . . . . . . . . . . . ~ . . ~ . . . . . . . . ' ~ GENERAL PLANT Land & Land Rights • • • • • • • 9 • • ~ • • • • • • • • • • 0 • • • • • • 0 $- Structures & Improvements ••••a••••••··········· Office Furniture/Equiprent • • • • • • • • • • • • • • • • • • • • • Transportation Equipnent ~ . . . . . . . . . . . . . . , . . . . . . . Stores Equipment ••w••••••••••••••a•••••e••••••• ~ls Shop & Garage Equipnent • • • • • • • • • • • • 0 • • • • • Laboratory Equipment ••••••••••••••••o••••••e••• Power-operated Fquipn:mt •e••••uo••••~ •••••••••• Ccmnunications Equiprent • a e • • • • • e • • • • c o • • • • • • • e Miscellaneous l!quiprent • • • • • • • • • • • • • • • • • • • • • 0 • • Other Tangible Property • • • 0 • • • • • • • • • • • • • • • • • • • • 5 Stlbrota.l • • • • • • • • • • • • • • • • • • • • • • • • • • • .. • • • • • • • • • •• $ 5 Contingency •••••••••••o•M••••••••••••···~··•••• 1 TOrAL GENERAL PLANT • ~ • • • • • • • • • • • • • • • ~ • • • • • • • ~ s • (..;''. ··~ ~ Totalg { X 10 .) $ 2,509 L~ $ 2,515 \;) ·~ ~-,;..; () ~2-:~ Remarks ~ ~ --~.=s ~ :..:.:==• D~cl~~ed under 330 Included tmder 331 Included 'tlr'rl.er 399 Included under 399 Included ·under 399 Included under 399 Included under 399 Included under 399 Incltrled under 399 Included under 399 Included. under 39S Sheet 3 of 5 .. ·' ·.~- s· e-"< ,._) : ~ .. -.. . r:~ .• 0 . ...., 1~: .. ~ _0 REVISED TABJ.JE 0.2 (Cont:d} -~'~ ~,._.,..,~ -.:-_-~ ~,-:-~-"'~~ ._ ~-,.._~ ,~,..,.. .._ ~,..... ...,.~ Line Number Description TOTAL BROUGHT FC~~ ···~··••••••m••••••••••••• INDJ.REX:.'T COSTS Temporary Construction Facilities • • • • • • • • • 8 • • • • ConstvJction Equipment ••••••••a•••••••••••••••• camp & carmissary • • • • • • • • • • 0 • • • • • • • • • • • • • • • • • ~ • I..a.}x:)r ~11se •••••••••••••• o •• o ...... -. •••• o • D ••• SUperintendence ••••••••••••••••••••••a••••••••• Insurail~ •••••• o ••••••••• a •••••• ,. ••• ::» •••••• tt • a • H.:i.tigation • • • • • • • • • • • ~ • • • • • -• • 5 • • • • • • • • • • • • • • • • Fees ••••• Ill •••••••••.• a -t'l • fll! ft ••• -• o • • • • • • • • • • e v e • ~ Note: Costs under accounts 61, 62, 64, 65, 66 and 69 are included in the appropriai:e direct costs listed above. Subtotal Contingency ............ o ................ .,g ••••• ~ •• TOI'AL INDIREX:T COSTS • • • • • • • • • • • • • • • • • • • • • • -* • • • ·~ ~ /,; --~--1 (~~) $ 302 29 $ 331 48 :~ 'lotalE ( X 10 ) ~ I -~-t $ 2 .. 515 . $ 379 $ 2,891 ·~ ·.~ ... ,~ ~~ ;:::~ . :~· ' ~!!II· Rercarks See Note See Note ~"'" ._) See Note See Note See Note See Note ~ )· ,, '----" Sheet 4 of 5 u. -----· ~,-~-·~-·-----~,....,··.. . ~~----~~-.---~:;r-~~~,-'•'"""'""....,•'lltii!W'iM'+ U$11 4A$ QM;:.--~~ -_:::_, ~:~·/ ( ::.:: -- \! _./~~ .. "" () REVISED TABLE D.2 (Cont'dl ~-·~·~-_..,. ...,,;'~ -':::,.~ .. -":"--'"":::-~ "'1r"r.c.-~"'ti~Jtt ~":r:a.-"..ll; ·~ Line 1\\lmber 71 ~- ,_ ·- DescriEtion TOrAL BRCUGh"T FORWARD • • ~ • • • • • • • • • • $' • • • • • ~ • • • • • • _9VERHEAD CaJSTRUCTICN COSTS (PROJEX:'T INDIREX:.'TS). Engineering/Ad1rlniRtration and . ' 1 . . . Env1ronmenta Mon~~or1ng •••••••••••••••••• legal Expenses • • • • • • ., • • • • • ~ • • e • • ~ • • • • • • o • • • e • • • Taxes • • • • • • • • • • • • • • • • • • • • • • • o ~ ·• • a • • • e • • • • • • • s • • Mministrati ve & General Expenses •••••••• , • o ••• Interest ••••eG•••c •••••••~•••••••••m•••••••o••• Earnings/Expenses during Construction .......... .. 'lb"ta.l ()\Yeif".!E!a.d • ~ • • •• 0 • • • .. • • • • • • • • ., • • .. • • • • • • • • 0 • TC!I'AL PRo.JEX:T COSTS -January 1982 Price revel. . ..........,. ~ ••• -· c .• J J'JrounG ( X 10 ) $ 467 .) ,,~ ~~ '~· _) ~ 'Ibtal~ _Lz 10 ) $ 2,894 $ 467 $ 3,361 ·~ ·~ ,_ ·.-.... ~· -~ Remarks I I Included in 71 Not Applicable InclUaed 1n 71 Not Included Not Included . " . ~·. 1!!1. ... _) . j I ~ r_./ L~ ,_ -~--1~-~-_ _ ~-, , -.:::.5..:~. ~ .... --~ --~ -,._ ,, . ·~'Y">;, ~ } :~ ! ,~ , ___ ,:.r.j . . ' JJ · J • • ·r • ~ • 'i ,. ... '. ". ~"-·--~ '<-i.. ·""--~-::-:-~. -~-·~""'t""t--'\ol Line Numl.Jer 330 331 332 333 334 335 336 t'";;~ \, ~~ ~~-'"''1;\"::""t ~~ --,__...,..,., - ,,._.., .,_,_., .J ·--1 ~ ~ j ' J ~ _.J REVISED TABLE D. 3: ESI'IMATE St.Jw..W{Y -DEVIL CANYOO JANUARY 1982 PRICE LEVEL " .. Description PRCDOCI'ICN Pimi' Land & Land Rights -• • • • • • 0 • • • • • • • • • • • 0 • • 0 • • • • • • Powerplant Structures & Irnp~nts • • • • • • • • • • • Reservoir, Dams & Waterways •a•••••••••••••••••• Waterwheels, Tul:bines & Generators .............. Accessocy Electrical E:Iuiprent .......... :. ....... . ~ti.scel1aneous I\:Merplant Equiprent (Mechanical) Roads & Railroads • • • • • • • • • • • • 0 • • w • • • • • • • • • • • • • • Stllltotal • • • ct • • • • • • • .. • • • • • • • • • • • • • • • • • • • • • • • • Q • • Contingency • e • e • ~ • • • • • • • • • • o • e • e • • e • o • ~ e • • ~ • • • • '.IDI'AL PROOUCTION PLANT e e a A a e • e • e • • • e ct e • • • 0 • • e 0 • Arroun~ ( X 10 ) $ 22 74 577 42 14 11 118 $ 858 125 'lota1g ( X 10 ) $ 983 -~ I I -~ '"~ Relnarks ~ ., .. ·-~ =~~ ·. ~· _j ,; " -; ... ,_/ L ~-~~--~--~-~~~---------~ -~ ... -~::.~~~--·-·-.. ~ ---:..::;:::·~· ~,..;~ .-.:\ -~·~"~ .. ~-=-~·:::"\~ .i:. L:.tne Number 350 352 353 354 356 359 -...,.-"J"·"-r';,-~~~ -~ ~~ . .,.....,_..--;>~- ' Description 'JUrAL BROOGHT FORWARD • • • • • • • • • • • • • • • • * • • • • • g • • • TRANSMISSIOO PIJ\NI' Land & Land Rights • • • • • ~ • • • • • • o ·• • • o • • • • • • • • • e o • Substation & SWitching Station Structures & Imp~vements a••e•s••••••o••~·········•o• Substation & SWitching Station Equiprent • • • • • • • Steel To\vers & Fixtures ••••••••••••.•••••••••••• OVerhead Conductors & Devices .$~·······~······· Roads & Trails • • • ~ • • • • • • • • • • • • 0 • • • • • • • • 9 .• • • • • • • Subtotal • • • • • • • • • e • • • • • • • • • • • • u • • • • • • • • • • • Q • e • • Contingency • • • • • • • • • e e • • • • • • • • o • ~ • • • • • • • • • • • • • • TOrAL TRANEiMISSIOO PI.J\NT ......................... . -~ ' ~ ' ·• (~~) $ 0 7 21 29 34 0 $ 91 14 --1 ·~ ' . .J Total~ ( X 10 ) $ 983 $ 105 $ 1,.088 --, • ~ ~~t-"i 'l!~l., ~·~-~:·~:~---=~ t :· .. _.4-·_:;..~ Rem:trks Included in Watana Estimate Included :i.n Watana Estimate . I ..,,,- ~ ·~ \. '~ .....,..,.~ L_ -----~ --~ .•. ~ ' -~~ :.:~.~--~ \ __ ~ (\ ~ ""'-~;:-~ ""-• ~l.J ·."i -~--~ I . REVISED TABLE D.3 (Cont 1 d) Line Number J89 390 391 392 393 394 395 396 397 398 399 r~-y ;:;-:-+--:· -·-::;::. -~» r ~ ;';'_ '""-'*'> ;~ ~~ ·-.,_ ·-,_;;.. ,J Description TarAL B~ FORWARD • • • • • • • • • • • u • • • • • • • • • • • ~ • • GENERAL PLAN!' I..a..rlCl & I.aOO. mghts . e I. 1-1 • • • e e •• e e e II: •••• e e e a e •••• e • Structures & Inpro~ ·;~!Lts •••••••••••••••••••••• Office Fumit.ure/Fquipnent • • • • • e G • • • • • e ~ • s • • • • • Transportation Equiprent • • •• a • e • • • • • • • ~ • • ~ & • • • • • Stores Et}ui anent .......... .., ....................... . Tools Shop & Garage Equipnent • • • , o • • • • • • o • e • • o • Laboratory Equipment ............................ . ~~ratoo Fquiprent • • • 0 • • • • 0 • • • • • • • • • • • • • • Ccmmmications Equip:rent • • • • • • • g • • • • • • • • • • • • • • • Miscellaneous Equipnent • • • • • • • • • • • • • • • • a • • • • • • • other Tangible Property • • • • • • • • • • • • • • e • • • • • • • • • Stlb~l •••••• eli • ft •••••••••••••••••••••••••••••• Contingency • • • • • • • • • • 0 • • • • • • • • • • • • • • • • • • ~ • • • • • • 'l'Ol'AL GENER.1\L PI.J\Nr • • • • • • • • • • • • • • w • • a • • • • • • • • • • ~ ~~ ,J (~~) $ 5 $ 5 1 ~ ~ J j Total~ ( X 10 ) $ 1,088 $ 6 $ 1,094 -~ .) ~ -:;J .,.......... -~ ~~= ~--:::~1 ~~! •• 1Jf'~· ~~~-...... , • J~::.~, • Remarks Included und~: 330 L~cluded under 331 Includei under 399 Included under 399 Included under 399 Includ(~ under 399 Included tmder 399 Included under 399 Included urlder 399 Included UI1der 399 ' j __ .1 • I, •,, • .I ~,..../ L"<'><<-<--~ -~ ~~-~.··· --~::~,.:: .. : ...... --·~· II ..,;;::_ ol --'".---: -'-. Lme ~umber 61 62 63 64 65 66 I I 68 69 -~~ ~ --~ Description 'lm.AI.. Bmil'W' ro~ ••••• It ....... D ••••••••••••• INDIRECI' COSTS Temporary Construction Facilities • • • • • • • • • • • • • • Construction Equipment • • c • , • • • • • • • • • • • • • • • • a • •· • camp & Ccrcrnissionary e e G e • e • e 0 e • e Q ~ e • e • e 0 0 0 0 e • e e In.OOr ~se e • 0 e e e s ••• e • e G e • II 8 • e e e • .;: e • e e e e 0 e e • SUperintendence • • • • • • • • • • • • • • • • • • • • • • • • • Q • • • • ~ • InS'Urance ••••• 9 ••• o •••••••••••••••••••••••••••• Mit:igation e e e 0 e ~ e • e • • • e • e 0 e • • e e D e e e e e 0 e • D e • e 0 e a Fees •••••••••••••••••••••••••••••••••••••• o •••• Note·: Costs under accounts 61, 62, 64, 65, 66 and 69 are includ~1 in the appropriate direct costs listed above. SUb-total e 0 • e • e D W • e e e 0 0 e e 0 e • e •• 0 a 0 CJ e 0 e e • • D • e e • • 0 Contingency •••••••••••••••••••••••••••••••••••• 'IUI'.AI.. lND~ COOl'S ••••••••••••••••••••••••••• TOQ'AL CONSTRUCTION COSTS •••••••••••••••••••••• -~ (~~-~) __ , $ 145 4 $ 149 22 -~ ~ J Total.g ( X 10 ) $ 1,094 $ 171 $ 1,265 ~'!:"··~ !.:'_;~~ Rerrarks See Note See Note See Note See Note See Note ~ -~·:: '~:""J See }.Tote ' ::':. ':t!:?l ' .. ) . ) "•l :·-/ LL S~t4of5 I - ........ -·"<•-"~--.... -.~ ....... -~.~~ .. ~·-·-.-.......... --~-.....,..... .. ~,-·--~~ . . .. ~ --.-. , .... -"M ~~~·-" j*Wff~-~~ A-1"~~~ ... ~ \'I -._.:;,: t\. -l- ,;). .,~ ,, -=---'* I ·u. I n·., ,.; Line Number -· 71 72 75 76 77 80 :-----~ ~?~ ---._ l)escripf2:on 'lUrAL COOSTRIJCTION COOTS BROll3HT FOJ:MARD • • • • • • • OVERHEAD CQ.\ISTRUcriCN COSTS (PROJOCT INDIRFCTS) Engineering/Administration and Environmental Monitoring •••••••••••••••••• Legal Expenses ································~ Taxes o ••••.••••••••••••••••••• o tt •••••• , .......... C!l Administrative & General Expenses •••••••••••••• Interest •••••••••e••••••&••••a••••••••••••••••• Earnings/Expenses during Construction ......... .. Tbtal Overhead •••••••••••••••••••••••••••o••••• TarAL PROIEX:T COSTS -January 1982 Price Level. ~ "l'.t".:~ (~~t)- $ 204 ·~ ~ Totalg ( .K 10 ) $ 1,265 $ 204 $ 1,469 ~ ~::• .,...jft ~:::a. _j .J ' "::J Remarks I I Included in 71 Not Applicable Included :i.n 71 Not Included Not Included -~···'~· .. ' .:-... : . ...-... : '""'·' ~ . -• J;)-.,.,__.j ... _, tt • } __ .., . .. .... ·· ... _/ C!'h.t-...-..4-l ... .c r: tJ&~\.o U.l. ;;J :; ...... ~.._.-·..-t.,".;,"~-,.. .. ~~-............ ~~-----'o" ........... ., ___ ~~----~-.----....,........_,~--"-~~ ·•·· ::;:-;.".....::~~ '"': "''.'"•r•~••a••s±±.,+e:'Z,__~~ ·: .. 1. i I 2. 3. .....,~.Mf..,.,..-~--4-'-' 4. I 5. I 6. 7. 8. 9. 10. ~~·'·''''" ' ... ,...._~ ·~ -~ ~ 't'!'!!~ ~ L ~ ·' ~~ ...) . . . . ........ ~·~ '!'.::'::~ 'f,c"""1f1, .;<, __ '!!'! 1.::: :;31 _,,J ...... <.,'.,. J.J f ~. --· .-• .I REVISED TABlE D .. 4: MITIGATICN MEASURES -Sillv1MAF.Y OF COSTS Th1CORPORATID IN CCNSTRUCriCN COSTS ESTIMATES JANUARY 1992 PRICE LEVEL COSTS INCOPORAT.ED IN CCNSTRUCriOO FSTTI-1ATES Outlet Facilities Main Dam at Devil Canyon ••••••••••••••••• Tunnel Spillway at Watana ................. Restoration of Borrow 1\rea D .................... Festoration of Bornow Area F ................... &storation v-f Camp and V1llage ................ Restoration of Construction Sites ••••••••••••• Fencing~ Camp •••••••o•o•~•••••••••••••a• Fencing around Garbage Disposal Area ............ Multilevel Intake Structure .................... Camp Facilities Associated with Trying to Keep ~rkers OUt of local Camuni ties • Restoration of Haul Roads ...................... SlJB~Al..J ••••••••••••••••••••.••• CJontingency ........................ e••••••••••••• TOI'AL COOSTRtx::TICl-l ••••••••••••• Engineering • • • • • • • • • • • • • • • • • • • • ~ ft • • • 0 • • • • • • • • • T(JI'AL PRCXTE:X:'I' .................. . "":"~_..,,._,~~·'"'"".........,.";--:'".__,....,_ __ ~ _,,..~·~L ,?'___.7-"''""""'""""""'"'.,..,_..,.:..,.,.__._..,..,._.,_,_ ______ ~ ~' WATANA-$ x--{o-::1 $ 53,.000 - - 1,100 11,500 "00 .:J - 21,200 9,900 - 96,800 14,200 111,000 14,000 125,000 ·-.............. DEVJL ~00 $ X 10 $ 12,600 ... - 900 1,500 200 - NeA .. 6,400 - 21,600 3,200 241800 3,100 27,900 - l I Ranarks ' I Included in 5 I~,cluded in 5 ll I: D Included in 6 • '" •} ' ' . '•J ~" s Inclooed in 5 152,900 ·~-----c~. --. ----"\.~~;y .. .,..-~~ l111~,,,. · ...,-: ,..M~i'il ,~ > ••• t? .. CJ r·, ~ .\I ~~..._1 I I •• L_ ~-· '- ;.;: • Year To 0 1 2 ... .j 4 5 6 7 8 ~1 10 11 12 13 '14 15 16 * . ' _ _..... -~ ~-=-~= '!!!:.'.~.. ~ 7::"::>,..... t ;ll~ .•. -'1 ..._ _~ ... ~·~ r . ... . ::. ~ r~-:":'-"'2iil! r:~---~ ;;_ .. REVISED TABLB D. 7 SUSI'.rNA HYDROELECTRIC PROJECT WATANA & DEVIL CANYON CUMMULATIVE AND ANNUAL CASH PLAN -January 1982 Dollars -in Millions Annual Cash Flow $ Cummulative Cash Flow (To End of Year) Watana 104,.9* 238 .. 7 311 .. 9 262 .. 4 484 .. 5 475 .. 4 477 .. 0 465 .. 6 288~5 17.0 .. 6 81 •. 4 Devil Canyon 45.8* 79.4 52.2 81.4 39.6 72.6 151.7 237.4 250.6 241.1 193.2 23.8 Combined 150.7* 238.7 311.9 262.4 484.5 475.4 556.4 517.8 36.9 .. 9 t 210.2 154 .. 0 151.7 237.4 250.6 241.1 193.2 23.8 I Watana Devil Canyon Combined 104.9* 45.8* 150 .. 7* 343 .. 6 45,. 8 389.4 655.5 45.8 701.3 917 .. 9 45.8 963.7 1,402.4 45.8 1~4.48.2 1,877 .. 8 45.8 1,923.6 2,354.8 125.2 2"480.0 2,820.4 177.4 26997.8 3,108."9 258.8 3,367.7 3,279.5 298.4 3,577 .. 9 3,360.9 371.0 3,731.9 522.7 3,883.6 760.1 4,121.0 1 ,.o1o. 7 4~371.6 1,251.8 4,612.7 1,445.0 4,805.9 1,468.8 4,829.7 Estimated costs related to engineering, administration and environmental studies expec·ted to be incurred prior to issuance of FERC license and prior to beginning of construction. I _) .. ~:.~ ""~-'""'-'"'""_,~'T-'-"'''-""..,.'"'"'""'"--..--,•··,.....-t-,........_~,.,.--·~----..._~-.--..... --.,........_..._..."'-....-_..._,....._.._.~""'7 -~~' ..-.,-;~~~,.... :1 I S. $4J Mij Jj$ d$L +OCi A& a ..... -•~ Jj'\::. ' 1/ ,;!~/ () 9-~ '• ~---, I, ,-;.:. ;I -· I ~l "" 1 '·-" I Y@ar To 0 1 2 3 4 ~··".;--~ 5 I 6 7 8 9 10 11 12 13 '14 15 16 * .c --~·~~=c.-~ e:-=3 REVISED TABLE D.? SUSITNA HYDROELECTRIC PROJECT WATJl..N.A & DEVIL CANYON CUMMULATIVE AND ANNUAL CASH PLAN January 1982 Dollars -in,Millions "':~~ t"":-:JII Annual Cash Flow $ Cummulative Cash Flow (To End of Year) Watana 1D4 .. 9* 238.7 311 .. 9 262 .. 4 484 .. 5 475 .. 4 477.0 465.6 288 .. 5 170 .. 6 81.4 Devil Canyon 45.8* ?9.4 52.2 81.4 39.6 72.6 151.7 231.4 ?5·0 ,,. & • b 241.1 193.2 23.8 Estimated costs related expected to be incurred Combined 150.7* 238.( 311.9 262 .. 4 484.5 475 .·4 556.4 517.6 369.9 I 210.2 154.0 151.7 237.4 250.6 241.1 193.2 23.8 I Watana Devil Canyon Combined 104.9* 45.8* 150.7* 343.6 45.8 389.4 655.5 45.8 701 .. 3 917.9 45 .. 8 963.7 1,402.4 45.8 1,448.2 1,877 .. 8 45.8 1,923 .. 6 2,354.8 125.2 2,480 .. 0 2,~20.4 177.4 2,997.8 3,108.9 258.8 3,367.7 3,279.5 298.4 3r577 •. 9 3.,360.9 371.0 3,731 .. 9 522.7 3,883 .. 6 760.1 4,121.0 1 ,·010. 7 4,371.6 1,251.8 4,612 .. 7 1,445.0 4,805 .. 9 1,468.8 4,El29.7 ' 1'1" ~ II < w t • ~ •::~··"" . ' ) .,. . c. !• • • '.,J to engineering, administration and environmental studies prio~ to issuance of FERC license and prior to beginniwJ of LL.-·~~~·~-·---···-~o~s~ructi:n~-~c -·-·,r·--~·--~--~-r-· • --·"7.r---·~---_,.-,..,, ·-'*If"'' oM><ooo•MIIf ....... HCO;pAIIJ'4 c::::;. .-~ }. : "" ~ . .,' ',;..\;, (.:r .. !•: • ... "" BEFORE THE FEDERAL ENERGY REGULATORY COMMISSION APPLICATION FOR LICENSE FOR MAJOR PROJECT SUSITNA HYDROELECTRIC PROJECT PROJECT NO. ·7114-000 ADDENDU1·1 f TO EXHIBIT F SUPPORTING DESIGN REPORT (PRELIMINARY) August 1984 f j .. i l ~I • u.,J . ... , ,. I •:) I i ~ffi , • LJJ n· iL 1 . . """· FEDERAL ENERGY REGULATORY COMMISSION ·PROJECT NO. 7114 LICENSE APPLICATION SUSITNA HYDROELECTRIC PROJECT ADDENDUM TO EXHIBIT F SUPPORTING DESIGN REPORT August 1984 T A B L E 0 F C 0 N T E N T S 1. Intro~uction 2. Watana Dam Embankment 2"1 General 2.2 Design Criteria 2.3 Freeboard and Embankment Settlement 2.4 Dam Cross Section 2.5 Dam Material 2.6 Dam Embankment Stability Analy~is 3. Watana and Devil Canyon Spillways 3.1 General 3.2 Hydraulic Structure Operation -_j-·-·_··_·_I .• l"'fj I l :) . I j t,. J r li [' 1. ... SUSITNA HYDROELEC'l"RIC PROJECT ADDENDUM TO EXHI~IT F, SUPPORTING DESIGN REPORT Introduction This addendum to Exhibit F Supporting Design Report provides supplemental information concerning certain design refine- ment proposed for the Susitna Hydroelectric Project. The arldendum focuses upon the refined dam embankment and the hydraulics of the proposed spillway revisions. 2'" Watana Dam ErrJ)ankment 2 .. 1 General 2.2 The refined dam embankment will consist of a compacted core protected by fine and coarse filtars on the upstream and downstream slopes. The outer shells will consist of rock fill. The upstream inner shell will consist of cleaned, processed alluvium gravel while the downstream inner shell will be constructed of processed sand fillo These feasibility designs will be further refined and updated during the detailed design period based on detailed stability analyses and known shear strengths. The dam will be designed to provide a stable embankment under all condi- tions. Design Criteria To insure that the impervio11s core meets the earthquake resistant design, the following design features will be incorporated into the main dam cross section: The core foundation contact will be widened near the ends of the embankment to ensure seepage control during normal operating conditions and during a seismic event. Thick filter zones will be placed upstream and downstream from the impervious core to prevent breaching of the core from either post-constructio~ settlement and cracking or from any cracking resulting from a seismic event. The filters will be designed to be self- healing in case of transverse cracks in the i 1 - f) i _j rr '1 '" LJ_;; r L 2.3 2.4 .. ·-· core resulting from elther post-const=uction settlement or a seismic event. Downstream fine filter and sand fill zones will be designed to be capable of handling any abnormal flows t~,a t could renul t from transverse cracking at the core from post- construction settlement or a seismic event. The proposed width of the core will prevent arching of the ~ore caused by transfer of load from the core to the filter materials and s~lell .. Compacted river alluvium gravel will be used to cover the downstream bedrock foundation, and compacted clean river alluvium gravel will be used to construct the upstream inner shell to minim~~e settlement and displacement that could be caused by a seismic event. Sufficient overburden foundation will be removed to insure embankment stability during potential seismic events. Freeboard and Errillankment Settlement The design crest elevation is 2205 feet. The. potential seismic ~e~tJement of 0.5 percent of the height of the dam will be accounted for in the design b.Y 5 feet of additional , freeboard at the maximum sec~ion and 2 feet of additional freeboard at the abutments. Dam Cross Section The typica'.l t::.ross section is shown in Plate F6R. The upstream slope is shown as 2.4:1 and the downstream slope as 2:1. The upstream shell is composed of two zones, an outer zone of rock fill and an inner zone of processed gravel x:ill. Any oversize rock in the rockfill will be raked to the upstream slope. The central impervious core is symmetr i\::al about th~e axis and has upstream and downstream slopes of 1~4; thus the maximum hydraulic gradient through the core will be less than t\¥o. Although t1--:.is is amply conservative~ it will be verified based on future laboratory testing. 2 .. - • • ' 0 • ... ~ \ (j, • • ,. j I. ~· I \ ~ .-;,, .. ~ . ! 1 • LJ r L [ r ! ~ I: L. IT u r u r H lJ .,..~., -... ) •' The c:o:te is separated f:rom the upstream gravel fill by a fine filter and a coarse filter, both of variable but ample thickness. The downstream shell is composed of an outer zone of rockfill and an inner zone of sand fill which constitutes the minus 3/8 inch material removed from the processed upstream gravel zone. The sand fill is separated from the impervious core by a fine filter, and from the ro'<r::fill by a coa+se filter. Below El. 1500, a compacted gravel blankets the bedrock foundation except in areas that appear erodible where a 5 foot layer of fine filter will be placed. Detailed design of the e~bankment zoning, gradation, placement and compaction will be finalized a~ter borrow explorations .~nd testing are complete,. Tb upstream and downstream filters are provided a~ protection against possible leakage through transverse cracks in the core that could occur ae the res ill t of settlemen.t:. or displacement during a seismic events The wide filter zones provide sufficient material for ~ealing of any cracks in the core and the size 6f the downstream filter zones will ensure its capcbility to handle any abnormal leakage flows .. The exterior shells of the dam will consist of compacted rock fillw To ensure rapid dissipation of excess hydrostatic pressures during a seismic event, the saturated upstream shell will consist of clean river alluvium gravels. This material will be processed to remove fines less than 3/8" in size. The downstream shell beneath the sand fill will consist of compacted unprocessed alluv- ium gravels ~ince it will not be affected by pore pressure generation during a seismic event. To guard ag~inst piping, the sand fill will be completely confined to prevent migration of fines in any direction. A fine filter will be placed, as required, over areas of foundation bedrock where severe jointing, weathering or rock altera- tion exist. Slope protection on the upstream slope will consist of a 40-foot rock raked zone of oversizee material. 3. J [ l !; I f I I l ·IT r L\ 1.~1 n u r 1 L: r l 'I l' <J r l ·' ......... _r ) ,... . ..... The typical crest detail is sho,.;n in Plate F7R. Because of the narrowing of the dam crest, the filter zones will be reducec ·tn width and the upstr~am and downstream co a ... .5e filter replaced with carefully gJ:-aded and selected shell materials above Elevation 2170. 2.5 Dam ~aterial Core The core material will be obtained from Borrow Site D, which consists of a series of glacial tills separated by alluvial and lacustrine materials. Processing and blend- ing will be nec~ssary to provide the required moisture content and gradation and to remove any oversize material. Howe,rer, information to date ir.tdicates this can b~ accomplished by selection of a vertical-face mining method and on-fill processinge Material t.Yill be placed in 9-inch uncompacted lifts at a maximum moisture content of 3 percent above optimum moisture content, and compacted to 95 percent of the maximum density obtained from the Modified Proctor Test (ASTM D698). Fine and Coarse Filters Fine and coarse filter material will be obtained from Borrow Sites E, I, and J. Borrow Site E is the preferred primary borrow source for all the filter and shell fill material in the dam. The material will require processing to provide the proper gradations for the fine and coarse filters. Interior Shell Fill Material ---------~---------~----- The shell fill can be obtained from :Borrow Areas E, I, and J. The upstream shell will be constructed using processed river alluvium gravel ,tlith no more than 10 percent of the material less than 3/8 inch. The downstream shell covering the bedrock foundation wiJ1 be constructed using unprocessed alluvium fill material, with the sand fill accomplished by mixing of a carefully controlled byproduct 4. -_J '~ ,; !1 l ' . \ l t.'{ . .. LJ ,. ! ~ '' I L' F' I: '' '' L-' r j. w r I u r ; l L£ [1 I' l u I ! 1J 3. resulting from production of the filters and processed gravels. Rock Fill Material The rock fill material will be obtained fro1~ Quarry A, and rock from required excavation:;;. The rock raked material will be placed on the entire upstream slope, and in certain areas of the downstream slope of the dam as protec- tion against wave overtopping and toe erosion .. 2. 6 Dam Embankment Stability Jl...nalvsis For seismic stability the dam embankment as designed is considered to satisfy all present day safety criteria. Moreover, proven effective defense measures against seismic action have been employed, such as large freeboard, large filter and drainage thicknesses, along with the use of a free draining gravel and rock fill zone at the vulnerable upstream slope. Static and dynamic stability analyses have been performed to estab- lish the upstream and downstream slopes of the Watana Dam. The analyses indicate stable slopes under all conditions for a 2.40 horizontal to 1.0 vertical upstream slope. Therefore, these slopes have been adopted for preliminary design purp0ses. Although small portions of the sandy gravel c~.1d gravelly sand alluvium remain beneath the upstream and downstream toes, the dam will rest on bedrock over approximately 80 percent of its base. This will en~ure that the dam will be stable even tho~gh inconsequential shallow slides could occur. Watana and Devil Canyon Spillways 3.1 General The proposed single service spillways at both Watana and Devil Canyon will be designed with hydraulically efficient approaches, which will pass the project PMC described in Exhibit F with the same or slightly greater freeboard on the dam crest as compared with that shown in the License Application. ~-~spillway crests will be shaped to preclude suL _mospheric pressures greater than one half the design head. 5. -· ' L_; ~~ u n L.:.J ~·~ ' I ' • ...J P'.' I{ ~j I ~J .• ) .,..-"\ ' . ·-' .. The abub~ents and piers will be shaped to maintain contraction coefficients no greater than 0.025 and 0.01 respectively. The spillway crest approach channel relationship will be such that the dis- charge coefficient (Cd) , at design head, will be no less than 3.84. Where 1 Q L H 0 Q = Cd L Hol .. S -spilli.\lay discharge -net crest length -design head of spillway The chute will be designed to smoothly transition the flow from the crest down the chute and to flip the discharge dcwnstrearn to the river channel. Aeration slots will be located along the chute for air en .. c.rairut!ent to reduce cavitation erosion. The flood discharge and reservoir surface eleva- tion at Watana and Devil Canyon are presented in Figures 1 and 2 respectively. 3.2 Hydraulic Structure 0Eeration The inflow hydrograph, at Watana and that routed through Watana at Devil Canyon, for all floods with a recurrence period of 50 years or less can be discharged without using the spillway, through the outlet facilities and two units of the power- house. At Watana the reservoir would surcharge no higher than El. 2193, whereas at Devil Canyon the reservoir would not exceed the normal maximum level of El. 1455. For events in excess of a 50 year flood, the spillway gates would begin to open once the reservoir possed El. 2193 at Watana or El. 1455 at Devil Canyon. The gate openings would be adjusted to maintain the preceding reservoir elevations. In the case of the PMF flood, the g.a tes would eventually be fully open and the reservoir would begin to rise. When the reservoir begins to rise, the powerhouse discharge would be te~ninated in the routing study, leaving only the outlet works and spillway to discharge the flood inflow. 6. ; r t