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<br />- ,'.....,::.,;, ).." ,: ~,,; .".
<br />. ,designed to provide pr~e~i~al1y eomplete' prdt?etion from all floods up
<br />.,to;.;j;he:.'standaict:--project ;flood or 6.46 inenes .of ; runoff . Hydrologic
<br />studies snpw.tn;aj:. the r.equiredstorage forcontrplof tne standard
<br />..,.proj eet flood is _ abO\lt'd61. acre-feet,. tne Mopted..flood-eon trol storage.
<br />. .~ Irt:grder, tp ins1,1r\l. a high degree of s"curi ty; against failure of the dam,
<br />an uneontrotledspil1way:ogee weir, 75. feet wide,would be provided in
<br />the left abutment. A spillway design flood wi.th a peak discharge of
<br />,:.6,500 cubic;f'eet per second and :a .volume"of 16.9 inches o.f::.runoff was
<br />.cieveloped . and routed throllghtl:1e reservoir toaetimnine themaJl:imum
<br />'<Jater.sunfiace. The maximum water surfaeeelevation res\lU.ing from this
<br />routing was. computed to be 6218.2, 'with a peak discharge.of 5,800 cubie
<br />.feet per second. A freeboard .of 5 .J, feet was adopted, establishing the
<br />topo,(th~.da.m a televa tion622J .5.
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<br />5-0J. . G.eologics.l and foundation conditions. -.The Pinon Canon Dam
<br />s:j.teis located in the transitional zone of tnehighlands1",hich form the
<br />eastern slope of the Roeky Mountains, Ih this .region .the geologieal
<br />formations are sedimentary beds of Cretaceous period consisting of
<br />carbonaeeous shales and sandstones. Field investigations of the site
<br />and laboratory tests. of foundation materials obtained by subsurface
<br />exploration show that foundation eonditions at the dam site would be
<br />sui taqle for oonstruetion .of. .an earth-fill. dam. A geologie seetion of
<br />the d~m site.is Ehown on plate.J.: .
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<br />5-04. Gener:al.design criteria and assumptions. .- .The embankment,
<br />. hydraulie, and struetural design of the project structures .are all in
<br />aceord. with recommended praetices.. Design procedures. and methods util-
<br />ized .areb"sedon theoretieal andempi:r'1.ca1 analyses'. in general use,
<br />supplemented by results of model studie.s, for .similar structures under
<br />,comparable conditions. Design .eri teria .and assumptions used are out-
<br />l:i,ned in appendix II of. this report.
<br />
<br />.VI - DESCRIPTION OF PROPOSED STRUCTURES AjlJD ll'IPOOmIENTS
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<br />, " .'
<br />6,..01. . Dam. - The dete~ti(:>n dam'yJQuld be a rolled~";arth fill,
<br />695 feet long with a .erest width. of .15feet, and rising. about 7J feet
<br />above the arroyo bottom. The upstream embankment side slope would be
<br />1 on 2 fr,omtopqf dam (elevation 622.3.5) to elevation 6211,"1 on 2.5
<br />from eleV?-t:i~:m 6211 to elevation 6198 arid 1 .on Jbe16w:elE,.\t,l.tiori,6198.
<br />.Downstream s.ide slope. would .b<;l..l, on 2 from top of dam to. elevati.on ;
<br />6211 and 1 or: 2,.:5 .be.1qwe;Levation621l., Slopes: both upstream l:lnddown-
<br />stream would be proteeted by a grass eover. The embankment seetion
<br />would be constructed of imperNious' random fill obtained from borrow
<br />pi ts in the reservoir area. Embankment stability analysis by the
<br />critiea.l',o,ircle..jlle:thod indic.ated the. f.ac.tor.'. ,of. 'safety .against sliding
<br />t.o. be about. 1-.46. downstream; and aboutl.iJ:for:ilj:lstireani sudden .d:raw-
<br />dO"Wl1'.con.ditions. The' general .plan, typical- se:cti.ons, and details of
<br />the embankment are shown on plates 2 and 3.
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