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CRAPTfRFIVE Draft E!S Relrlsions <br />• Tertiary Uinta Formation sandstones and mazlstones. The alluvial material is generally <br />permeable; however, clay lenses may create azeas of low permeability or even impermeable <br />intervals. Alluvium thicknesses at the Piceance Site aze variable. , ' <br />American Soda's alluvial aquifer monitoring well 21-2, which is located in <br />the alluvium of a tributary drainage to Piceance Creek, penetrated 95 feet of alluvium. The depth <br />to groundwater in well 21-2 is approximately 70 feet bgs, indicating a saturated thickness of <br />about 25 feet at this location. in contrast. test holes drilled at the confluence of Piceance Creek <br />and Rvan Gulch. iust south of theproiect site, penetrated 70 feet of dense organic clay (Welder <br />1987). Groundwater flow within the alluvial aquifers is controlled by topographic slopes and <br />stream flow directions. Therefore, groundwater flow in alluvium at well 21-2 is expected to be <br />to the east. <br />Alluvial groundwater at the Piceance Site is represented by analvses from American Soda well <br />21-2 (fable 3.4-2) and is classified as a sodium bicazbonate type. TDS values measured in 11 <br />samples collected during 1997 and 1998 range from 634 to 2,292 meJl, with a mean of 1,680 <br />m_g/I• <br />~, ~ ...,... , cAn ..,,,n ~s These TDS values falls within the range observed over the entire <br />1 <br />basin of 470 mg/I to 6,720 mg/I (Weeks and Welder 1974). The mean values for TDS (1.680 <br />m~/1), sulfate (616 mgR), iron (2.11 mg[I), and manganese (0.18 mgLl) exceed Colorado <br />i~roundwater standazds. A single analysis performed for aluminum suggests that this parameter <br />exceeds the aericultural standazd. The standazd for chloride was exceeded by one reported value <br />of 1.047 me/l. However, this value is more than 12 times hieher than the next hiehest <br />• concentration recorded for chloride in this well (87 mQ/I) and is, therefore, considered to be <br />suspect. The standazds for chromium and lead were also exceeded in 1 of 19 sam~es each. <br />A search of the USGS database was conducted to obtain water quality information for the <br />alluvium and other water-bearing units neaz the Piceance Site, alone the pipeline route, and neaz <br />the Pazachute Site. Table 3.4-3 provides a summary of the analytical results for wells neaz the <br />Piceance Site. and the raw analytical data for these wells are included in Appendix K. TDS <br />values from three wells completed in the alluvium ranged from 990 to 6.710 me/1. Mean <br />concentrations of TDS (3,080 me/l), sulfate (357 mpJl). fluoride (11.5 meA), and manganese <br />(0.09 mg/1) exceed Colorado groundwater standazds for these wells. , <br />Paee 3-19 <br />. 1.,... a..~_,. a,n:.... ,.r..u,,..:a .., . <br />- ,:.,.~_,....en ~, ~ <br />w• <br />rr .......r.o <br />m ., /ACn.,,,.m ...,a.,, a/ no,n.....me ..,.a..a <br /> <br />Qllt1^°' .e... n ..,YI:..b ..t.,,.,.,:a..«.. <br />,.ell 71 1 1........ t6.. <br />a e-.,1 .,l, e..,:.,.,1 ., a ..A A <br />S <br />a <br />r.11~ni0(jn RFnlln(j1 '•tL.s^t^^'1.,.A.. TL„^^:.,. z <br />+v+~ms <br />,1.,,1„ „1. L...:A <br />/1 nA^/. <br />,, n\ IC /C[n <br />nnn n\ <br />/n nn <br />, <br />: <br />n <br />.~,..., <br />...., <br />~ <br />.,, <br />, m .,,,.n\ ., /n c . <br />\ ,. , n ..,..m .... a .......... . ...... m ncc n o , .,, n\ <br />Upper Aquifer <br />• The Upper Aquifer is generally defined as the saturated wne that includes the lower, saturated <br />portion of the Uinta Formation and the upper Parachute Creek Member of the Green River <br />5-11 <br />