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<br />;dright Jlc Laurhlln Engineers <br />October 7.2, 1373 <br />• ( Page 2 <br />Tl:e fioaring Forh River parallels tt:c wc,tcrn side of the silo in n <br />deep canyon about 120 feet belo:r and 200 fret lc. the tacst of the t:~:,tarn <br />ed,c of the disposal area. Yloody Crcuk joins the Roaring Fork River obout <br />0.3 miles north of the northern limit of tltc site. .Jo major drainage <br />systems cross through the site. Yost precipitation t~+hich falls at the site <br />infiltrates directly into the upper soils. <br />j An autorobile race track is located adjacent to the southern end of <br />f [he s1te. /ltrater well has been drilled near the race track. The terrace <br />~ surface is covored with sagebrush and cluarps of grass. <br />Sltc Geology: The disposal site Is underlain by a relatively thick drposlt <br />i of Pleistocene age out:aash gravels. These gravels t:rere deposited by high <br />' velocity streams issuing from glaciers several miles up valley to the south. <br />' In general, these deposits arc coarse grained ranging from sand to boulders <br />although some floe grained tenses or pockets a+are deposited 1ri places. <br />Underlying rite glacial outr+ash gravel Is the Cretaceous age Ffencos shale. <br />This bedrock crops out along the road cut and terrace escarpment beloo-r the <br />southern half of the disposal area, based nn these outcrops, we Infer ilte <br />gravel-shale contact is about GO feet below the surface site. <br />Subsoils in the lrnmedlatc area of the disposal site were investigated <br />• , by drilling S shallo~.+ test holes. The dense gravel and cobbles made drilling <br />very difficult, and auocr refusal r+as r.:et in each test (tole. (Deeper drilling <br />would have required special equipment, and based on er;posuces of the soils <br />• In the adlaccn[ cscarp~ents, it was no[ felt that additional d,rillinq would <br />add to the kno~+ledge of [he site. As discussed above, exposures in the road <br />cut and river terrace indicate that at least 60 feet of the oytwash material <br />overlie bedrock. <br />Except for erratic Deposits of fine grained soils, the subsoils are <br />'fairly uniform. The dominant soli texture is a mixture of cobble and gravel <br />with occasional boulders In a silty, clayey sand matrix. Occasional pockets <br />of sandy clay occur t+ithln this stratum. Grain size analyses Hof typical <br />soils exclusive of Lire cobbles and larger gravel are shown on Figs. 3 and 4. <br />These soils are very dense and fairly tlgltt because of the well graded, <br />smaller grained soils packed around the cobble and gravel. <br />Percolation Tests: Percolation tests were performed in the test holes and <br />in shallo:a test (toles offset from the deep holes. The shallow level was 2 to <br />3 feet deep. Percolation tests tzre performcil by cleaning the'hole and adding <br />water to maintain a fairly constant level In the hole. The rate at which <br />the r:atcr percolated out was tir•.ed. Ti:esc tests were generally run In <br />accordance with the requirements of the Department of health, Education and <br />Nclfare for septic syster,.s. Tt,e results of the tests are tabu~latcd on <br />Table I and Indicate rates for the shallotr tests ranglne from 30.to 50 minutes <br />per inch and rates for the deeper tests ranging from 40 to GO minutes per <br />•I i <br /> <br />j <br />ii <br />i <br />:. <br />