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r <br /> 2.1 Geologic Conditions <br /> The site is situated in the northern part of the San Joaquin Valley, in an area underlain by <br /> several thousand feet of terrestrial and marine sedimentary rocks The northern San <br /> Joaquin Valley has been a lowland area subject to marme intrusion, flooding and <br /> incremental sedimentation for millions of years The uppermost 1000 feet of sedimentary' strata consist of Holocene, Pleistocene and Pliocene sediments, including the Laguna <br /> Formation, the Mehr-ten Formation and the Valley Spring Formation The sediments are <br /> interbedded nuxed-fluvial and deltaic sediments, donunated by medium-gra.imed sand and <br /> silts Generally, thin beds of unconsolidated clayey silt, silty clay and sandy clay are <br /> abundant in this upper zone, which are laterally discontinuous over distances of several <br /> tens of feet <br /> 2.2 Hydrogeologic Conditions <br /> Ground water is present beneath the site at a depth of 29 92 and 30 40 feet below ground <br /> surface (bgs), as measured on 22 December 1999 in two of the three groundwater <br /> monitoring wells (MW-1 and MW-3 respectively) installed on site (Figure 3) The <br /> elevation of groundwater in MW-1 and MW-3 was calculated by EI at lb 90 feet and <br /> 17 79 feet below mean sea level respectively, based upon elevation data from Kier & <br /> Wright Civil Engineers and Surveyors <br /> EI is unable to determine the groundwater elevation in the third well (MW-2) due to the <br /> presence of floating hydrocarbons Thus, EI cannot complete triangulation to determine <br /> the direction of groundwater flow at this tune This will be completed and a follow up <br /> r letter will be forwarded to recipients of this report as soon as the floating hydrocarbons <br /> are removed and the well cleaned to permit normal groundwater elevation measurement <br /> ' and sampling activities <br /> s <br /> It should be noted that groundwater flow gradients are low in this area, and seasonal <br /> changes in water levels can, therefore, have significant effects on the apparent <br /> groundwater flow direction <br /> Environewirg,Inc. Pro)ed No.99-012.02 2 <br />