Laserfiche WebLink
C y <br /> a tP <br /> tl fi <br /> 4.2 SITE IIYUROGEp1AGY <br /> The site is underlain by silty to clayey alluvial sediments to a depth of 10-15 feet. Below that <br /> depth sediments become more coarse-grained,a sandy clay to sand or even gravel. These more <br /> coarse-grained sediments form two zones which extend <br /> from rano to n 20 eet and from thickness from 5to 40 feet <br /> a few feet <br /> below ground surface and are separated by clayOYFelow there are silty/clayey sediments,which <br /> ss(RW3) to 25 feet(MW12)(see Figures 4 and 5). <br /> are dry and in which white concr, tions fill voids and fractures to an explored depth of 40 feet. <br /> and are replaced by mostly clayey to silty sediments around wells <br /> Sandy lenses thin out eastward <br /> RW4,MW 11,and MW 12. <br /> Static groundwater was encountered at about 30 feet in the wells located along t11e western <br /> boundary of the site. Groundwater flaws northcasl in the direction of offsite wells MW 11 and <br /> aturated zone <br /> MW 12 where static levels it s<und r1 in byas 35 feet a stiff,dry,ow grade. Tile s silty clay ats39 feet. The zone is s capmes ab'.: <br /> ner in this direction where lE <br /> of producing enough water for all of the new wells to be purged and sampled property. <br /> Groundwater elevation ranged from-21.61 to-28.24 feet below mean sea level on 2 May 1991. <br /> Groundwater moves cast-northeast at a gradient of 0.01 ft/ft(f=igure 10). <br /> Due to continuous drought,groundwater levels continue to drop at an ever increasing rate. The <br /> average drop of the water table during 1110 last 6 months was 1.5 feet. HowOver,in March 1991 <br /> water levels rose slightly (approximately 0.4 foot),although levels began to drop again in May. <br /> timated from bailing,pumping, and injection tests con- <br /> Values of the aquifer transtnissivity esducted at the site ranged from 150 to 300 ft2/day(1,050 to 3,000 gpd/ft) (Table 5). The average <br /> transmissivity was about 200 ft2/day (1,500 gpd/ft), as determined from pumping and injection <br /> tests,which is equivalent to a hydraulic conductivity of about 7 ft/day (2•5 X 10'5 misec). <br /> Assuming an aquifer thickness of 30 feet,this is characteristic of silty sand (Freeze and Cherry). <br /> 12 <br /> e671r.(J139�71Y�+911n <br />