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Inta~e towers for me Foothills tunnel and treat/1'lf:'nt plant and me Aurora r:1rvefSJOn are under COnSlrl.JCtlOn on me no!lt abutment appr()}rJmiJleI~ ISO;r uostrwm a/the dam The FooltlJI/s-jntai<.e IS the larger of the rwo Low-lev€! v.-ew trom upstream shOws the double-curvature shape 0/ the dam Formwori-: near the lOp is for the ~ and oven'lOw sectIOns ai/he servICe s{)Illwal The doggmg OIarform and gale {JIers lor the outlet workS are DekJ... 6 An aSSOCiation 01 tnree engineering tlrms ...as retained to, ...-or,,- on tne Foolhllls ProteCt In general each 01 tne ltrms has lal<..en resPOns:blllty tor one malar SlruCfural element They Include $tronlia Sormgs DiverSion Dam- Harza Engmeenng Comoany 2 FootMs Tunnel ana access roads-DMJM-PMIDS Reisler Inc 3 Foothills Treatment Ptanl-CH2M-HII Englneenng seNlCeS halie fflcluded prede5lgr'1 stud'es_ environ- mental assessments final de5lQn, servtCes during conslrucllon, and on-$jte Inspecllon The Predesign RePJn, In '....hlCh a~ernalilie structural arrange- menls were compared and deSign Cnlerla established was compleled In 1973 and hnal deSlQn began soon ailer An enVl. ronmental assessment ,'o'as submlned to the resPJnSlble gov- ernment agenCies In 1974 and the final Environmental Impact Stalement.....aslssued In February 1978 Additional studIeS and review were reqUired pnor TO iSSUanCe ot the Federal Dredge and Fill (404) Permit al ,.,-hlCh lime the way was finally cleared for preparatlOn a! bid documents and the award of contracts The prinCipal construCliOn contracts were awarded In 197910 MOrrison-Knudsen Co lnc - SrronTla SPrings Dam 2 Shank-AnukovlCh/JV -Connecting tunnels 3 Manln K Eby Construction Company Inc - TreaTment planl and hrst section 01 lhe cleaN/ater condUit 4 C R Fedrick/Kassler Corp -Balance of lhe clearwater COndUit Slronlia SPrings Dam Strontl3 SPflngS Wlit be a 300-tHHgh multl-curvature arCh dam 30 Il thICk allhe base and laperlng to 10 il thick at the crest The slte IS located 6 5 miles up WaTer10n Canyon al a place where hard strong igneous and metamorphIC rocks form a local con- stnCllOn The canyon walls are sleep (about one hOrizonTal to one vertical) and form a nearly symmetncal V shape whICh IS deal tor an arch dam Operarlonal tealures at the dam Include eight low-level outfets tw'o SPillways, and two Inlake towers The purp:)se of the OuTlets IS 10 maintain downstream fiver flows when the reservOlr IS below lhe Spillway cresllevel The 4_ooo--cls ClP3CITy at the outlels WIIi be dlvded bel'....een four 72-mch conduI1S conlrolled by 48-Inch nng,el vaWes (whICh Will be used lor larger !kJws) and four smaller condUits controlled by tw'o 18-mch and two 8-lnch flng Jet vawes tor smaller releases The tree discharge valves Will be protected by conteal plug valves and trash racks A ninth COndUlI at about normal river level Will be aval!able to completely drain the reser. vOir 11 necessary The 1'....0 Spillways Wilt have a lotal discharge CloaCITy of ap- proXimately 90,000 cts A servICe Spillway located allhe center 01 the crest 01 the dam wlll discharge through three ungated openings IntO a plunge pool excavated In the eXisting fiver chan. nel The crest ot the servICe spillway Will be al elevatIOn 6002, normal reservOIr level The Shape ot the Spillway ogee whlCh wlil contine discharges to the plunge pool area IS SImilar to that 01 the Harza-deslQned Mossyrock arCh dam In WaShingTon whlCh has been operallng successfully for some 12 ,,,ears The auxlll3ry sOfllway IS k:lcated In lhe lell abuTmenl and con. Slsls at to operate, diSCharge well downstream of the dam Fk:)w through the auxihary Spillway Will be controlled by a 17 5-ft -hlQh earThllli fuse plug conslructed across the chure The Spillways are de- S1Qned so that Nows up 10 12,000 cIs (well above lhe flooc:l-ol. record} Will be handled by the servJCe SPillway ak:)ne At that