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i <br /> This Quarterly Monitoring Report summarizes the groundwater monitoring activities completed <br /> at the site on 28 March 2001 <br /> 2.0 SITE DESCRIPTION <br /> The subject site is located in the Southern part of the City of Stockton, California (Figures 1 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 /> Icompound, a vehicle fueling facility and a large parking area for tank trailers <br /> I2.1 Geologic Conditions <br /> The site is situated in the northern part of the San Joaquin Valley, in an area underlain by several <br /> 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 mixed-fluvial and deltaic <br /> sediments, dominated by medium-grained sand and silts Generally, thin beds of unconsolidated <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 /> 2 2 Hydrogeologic Conditions <br /> Groundwater is present beneath the site at a depth of 27 5, 27 90, 27 40 and 26 90 feet below top <br /> of casing (btc), as measured on 28 March 2001 in the four groundwater monitoring wells (MW- <br /> 1, MW-2, MW-3 and MW-4 respectively) installed on site The elevation of groundwater in <br /> MW-1, MW-2, MW-3 and MW-4 was calculated by EI to be at 14 48, 14 48, 14 56 and 14 55 <br /> feet below sea level respectively, based upon casing elevation data from Kier & Wright Civil <br /> Engineers and Surveyors <br /> EI utilized the groundwater measurements to determine the direction of groundwater flow and <br /> the groundwater gradient present beneath the site The groundwater direction of flow was <br /> calculated to be southeasterly at a gradient of 8 89x 1004 ft/ft <br /> I <br /> Environeenng,Inc Project No 01-003 10 Page 2 <br /> I <br />