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<br />'" <br /> <br />3718 <br /> <br />RUED! DAM AND RESERVOIR, COLO. <br /> <br />27 <br /> <br />Designs are subject to modification 3S additional infonnation becomes <br />a"aibble. ../1 <br /> <br />Geolfj(J?/ ~ <br />Pre.liminnl'Y g-eologic inn~st.igations in the dam find reservoir area. <br />,,,ere made in 1!)4(; and 1048. The Fl'yimTpan River, in flowing <br />west.ward to meet the Roaring Fork ]~ive'r, (~i'os~es a series of forma- <br />tions of Paleozoic. age. The damsite oecupies a nal'row gOJ'f.!e cut <br />into red-colored sandstones and shale~, the upper [J,lrt of t.he :Maroon <br />formation of Pennsylvanian a~e. These m:l~siYe strata dip steeply <br />(lownstrenm clue to fault.inO' ;lnd folding' in the loral area. Th~ ent.ire <br />1\farooll formation as expo;d in the vicinity appears to be about 2,500 <br />feet thick, with some 1,000 feet of upper red sandstones underlain by <br />1,000 feet. of llltel'nating bllfl'-~olored siltstones and li!llei-'tone~, in tUl'll <br />resting on a. bed of ~YPSI1J1l ex{~eeding- GOO feet ill t.ltil:kness. The <br />l'egionld stl'udure is that. of a pl1lllging antidine, the ri,:er cutting a. <br />steep canyon across the upper reu sandstune hogback, 1\"lth t.he basal <br />gypSlIlll being- exposed in the resen"oir 01' central anticlinal area near <br />Hllel1i. The g--ypsnm bed necessarily underlies the dam at a depth of <br />about LOOO feet. The int~l"\'ening limestones ,",'ill occur at less depth. <br />As it matter of jud~ment. the proposed reservoir will pl'O\'e s:ltisfac. <br />tory from n seepag-e standpoint. but. this conelusion must be checked <br />by deep drilling" lllHl detailed g-colog-ical work. <br />TIle immediate fmllldatioll for the dnrn consists of m\1ssiv(~ sand- <br />stone strata (1 to 4 feet. thick) with illten'ellillg sll<lJe layp-1's. These <br />beds dip (Jo\\"n~tream :~;)o to 400 .\lltl s\ rike llOl:thwestel{r -10'"'. The <br />roek is considembly jointed. nile systl.'llI ~t.rikes llorthen:-;t alld dips <br />8(10 to 900 to the southeast: tlw, otlw.r ~tl'ikl.'s northwest. flipping ,100 <br />to ;:;40 to the northeast. .A fault of unknown elwrndrr, dipping 700 <br />dnwllstl'eam~ Cl'osse~ t.he I:allyon illllllt'dintely upstl'eHlH from the dam. <br />The extent and sig-nitiC:l1l~e of this fault must be determined before <br />the g-eologica 1 situation is thoroughly Ul1del'StoorL <br />Eii!ht exploratory holes were ,lrilled in 1(148 at the dams;tc. The <br />foundation rocks appear ndequately stable for const.ruction of an <br />earth dam. Ifoweyer, further (hilling- is required to evnluate fully <br />reservoir and damsite ~eepage conditions. 'Vllter-pressul'a tests <br />indicate that grouting: will be. necessary to control seepage of water <br />1IIllIer and around the dam. . <br />Prospecting nnd testing of the several types of a,'nilable m[lteriah~ <br />wil) be necessary prior to design and eonstrllctio-n. It is probable that <br />~at.lsfaetor.r deposits of silt, sand, and g-rnve-I can be located in the <br />re!:iervoir a~'ea for impen'ious, semipervjous, a~l(l pen:iolls emb;~Jlk- <br />n~cnts reqUlred for the proposed enrth dam. brave]s In the nUlOUS <br />I'l\'er terraces nJ~d in the riycr ehannel, uerin'<l III part. from granitic <br />nnd metanH?l'plllC ar~as in the upper reaches of the Fryingpan River, <br />probably WIll .be SUItable for concrete a~gl'ep:ate. ClifTs of ~IaroOJo. <br />sfLJ.uIstones w.luch are exposed dowllstremn from the dlllllsite ~lppear <br />"utable for l"Jprltp. , <br /> <br />Cf)n~tructjo"n ~vpects <br /> <br />COJlstruc9on of the dam and respn.oir ',,"ill require the acquisition <br />Of~flbout 1.luOO acres of laml, 11l0~t of, which is in pl'ivflte ownl3rship. <br />T area. Includes about 2;)(1 Hcres of farmlands whieh are rlevoted <br />la gel)" to prodllCt.ion of nat.ive hay under irrigation. The rp,mailling <br /> <br />