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<br />RUEDI DAM AND RESERVOIR, COLD,
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<br />27
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<br />lCG3
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<br />Des.igns are subject to modification as a.dditional information bec.ome~
<br />fl\"aIlable. __/ .
<br />.-~..n'.,
<br />C('olu[f.11 ",
<br />Preliminary g-eologic investigations in tl.le dam an.d res~r,"oir ayea
<br />were made in If)4(; and 1048. The Frymgpan Rlver, ]11 flowmg
<br />westward to meet the Roaring Fork River, crosse~ i1.. ~eries of forma-
<br />tions of Paleozoic age. The~ damsite occupies a nnl'l'OW gorge cut
<br />into red.colored sandstones and shales, the upper part of the :Mal'oon
<br />formation of Pennsylvanian a~e. These massi,"e strata dip steeply
<br />downstream due to faulting and folding in the local area. The entire
<br />:Maroon formation as exposed in the vicinity appears to be about. 2,500
<br />feet thick, with some 1,000 feet of lIpper red sandstnnes underhin by
<br />1,000 feet of alternat.ing butl'-colored siltstones and limestone~, in turn
<br />resting' on fl, bed of gYPSUIll exceeding 500 fp.et, ill thlcknr.-ss. The
<br />reg-ional structure is that of n plull;:6ng' anticline. the rin:'l' cutting :t
<br />steep canyon across the upper red sandstone hogback~ with the basal
<br />g-ypSllIll being: exposed in the reservoir or cent.ral ullt-iclinal urea near
<br />Rnedi. The gypSlllll bed nrce~silrily underlies the <lam at ft depth of
<br />nbout 1,000 feet. The intervenillg limestones will OCellI' at less depth.
<br />As 11 matter of judg-ment, t.he proposed reservoir will prove snt.isfnc-
<br />tory from a seepflg-e sblIHlpoillt., hut this cnnelllsioll must be checked
<br />by dE'ep (lril]in;r and (letailPLI g:e()lo~iCid work.
<br />The immediate fOllllllatiol1 for the dam consists of mn~siYe ~nnd-
<br />~tone strata (1 to 4 feet thick) witlt il1ten'elling sl1,de lavers. These
<br />beds dip downstream :J:,O to -Joe> alltl strike, lloithwc.3terly ...\.(l0. The
<br />rock i~ cOllsiderahly jointed. One- syste-Ill strikes nOJ'tlwa~t :111(1 dips
<br />~Oo to ~1()0 to HIP sOllt.henst.; t,hr otlte-l' strikes 110l'thwe8tl dipping 400
<br />to f,.j.O to tIle nOl'the;lst. A fault of unknowlt e11<lracter, dipping- 700
<br />dowllstrellm, crosses the canyun illllllelliHtely upstl'e:lI11 from the <'lnm.
<br />The extent and sig-nitkanee of this fault 1I111Ht Le determined before
<br />the geologica 1 situation iH thorougllly understood.
<br />Ei,ght exploratory holes were drilled in lU48 at the damsite, The
<br />foundation rocks appeal' adequately stable for construction of an
<br />earth dam. Howeyer, further drilling- is required to e,'nliHlte fully
<br />reservoir find damsite seepage conditions. 'Vater-pressure tesi~
<br />indicate that. gronting- will be Jlecessary to control ,seepage of water
<br />limIer and around the dam.
<br />, Prospecting and testing- of tJle sf'.\"eral types of Hyailnble matei'i~is
<br />,"Will be necessary prior t.o design and construction. It. is probable that
<br />sat.isfactory deposits of silt, sand~ find gravel can be located in the
<br />reservoir area for impervious, semi pervious, flnd perviolls embank~
<br />ments required for the proposed earth dam. Gra\'elH in the various
<br />ri,.er terraces and in the river ehanneJ. deri,'ed ill part from O"l':lllitic
<br />find metam~rphic nr~as in the lIpper reaches of the Fryillgpal~ R.iver,
<br />probably wIll be sUltahle fnr COllCI'ete aggl'cgate, Oi tIs of Maroon
<br />8flll(L"itoncs which are exposed dowllstream from the uamsite appear
<br />,"itnble for riprllp. .
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<br />Const.ruction of the dnm find reservoir wi]] require the acquisition
<br />of about ],500 acres of land, most of which is in private ownership.
<br />The area, includes ahout. 2!)O acres of farmlands wl.il:h [ue de,voted
<br />~al'gely to production of nati,-e hay unde,r irrigntioll. The remaining
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