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r 2.0 SITE DESCRIPTION <br /> The subject site is located in the Southern part of the City of Stockton, California (Figures I and <br /> 2) The site is an essentially level commercial trucking facility, which contains an office <br /> building, two truck maintenance shops, a truck-washing rack, a small above-ground storage tank <br /> compound, a vehicle fueling facility and a large parking area for tank trailers <br /> 2.1 Geologic Conditions <br /> The site is situated in the northern part of the San Joaquin Valley, in an area underlain by several <br /> f thousand feet of terrestrial and marine sedimentary rocks The northern San Joaquin Valley has <br />` been a lowland area subject to marine intrusion, flooding and incremental sedimentation for <br /> millions of years The uppermost 1000 feet of sedimentary strata consist of Holocene, <br /> Pleistocene and Pliocene sediments, including the Laguna Formation, the Mehrten Formation <br /> and the Valley Spring Formation The sediments are interbedded rruxed-fluvial and deltaic <br /> sediments, dominated by medium-grained sand and silts Generally, thin beds of unconsolidated <br />� <br /> clayey silt, silty clay and sandy clay are abundant in this upper zone, which are laterally <br /> discontinuous over distances of several tens of feet <br /> I • <br /> l 2.2 Hydrogeologic Conditions <br /> Groundwater is present beneath the site at a depth of 25 62, 25 99 and 25 55 feet below top of <br /> I <br /> casing (btc), as measured on 20 April 2000 in the three groundwater monitoring wells (MW-1, <br /> I MW-2 and MW-3 respectively) installed on site The elevation of groundwater in MW-1, MW-2 <br /> I and MW-3 was calculated by EI to be at 12 60, 12 57 and 12 71 feet below sea level <br /> I respectively, based upon casing elevation data from Kier & Wright Civil Engineers and <br /> I Surveyors <br /> EI utilized the groundwater measurements to determine the direction of groundwater flow and <br /> I the groundwater gradient present beneath the site The groundwater direction of flow was <br /> I calculated to be southeast at a gradient of 0 0027 ft/ft <br /> I <br /> i <br /> i <br /> Environeenng,Inc, Project No 00-005 06 Page 2 <br /> t <br /> F ' <br />