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r <br /> r <br /> r This Quarterly Monitoring Report summarizes the groundwater monitoring activities completed <br /> r at the site in the second quarter of 2000 <br /> ri <br /> r 2.0 SITE DESCRIPTION <br /> r The subject site is located in the Southern part of the City of Stockton, California (Figures 1 and <br /> r <br /> r 2) The site is an essentially level commercial trucking facility, which contains an office <br /> r 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 /> r <br /> r 2.1 Geologic Conditions <br /> r <br />. The site is situated in the northern part of the San Joaquin Valley, in an area underlain by several <br /> r thousand feet of terrestrial and marine sedimentary rocks The northern San Joaquin Valley has <br /> r been a lowland area subject to marine intrusion, flooding and incremental sedimentation for <br /> r millions of years The uppermost 1000 feet of sedimentary strata consist of Holocene, <br /> r Pleistocene and Pliocene sediments, including the Laguna Formation, the Mehrten Formation <br /> r and the Valley Spring Formation The sediments are interbedded mixed-fluvial and deltaic <br /> r <br /> r• sediments, dominated by medium-grained sand and silts Generally, thin beds of unconsolidated <br /> r 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 /> r <br /> r 2.2 Hydrogeologic Conditions <br /> r <br /> r Groundwater is present beneath the site at a depth of 28 00, 28 25 and 27 90 feet below top of <br /> r casing (btc), as measured on 26 July 2000 in the three groundwater monitoring wells (MW-1, <br /> r MW-2 and MW-3 respectively) installed on site The elevation of groundwater in MW-1, MW-2 <br /> r and MW-3 was calculated by EI to be at 14 98, 14 83 and 15 06 feet below sea level <br /> rr respectively, based upon casing elevation data from Kier & Wright Civil Engineers and <br /> Surveyors <br /> r <br /> r EI utilized the groundwater measurements to deternune the direction of groundwater flow and <br /> r the groundwater gradient present beneath the site The groundwater direction of flow was <br /> r calculated to be southeast at a gradient of 0 0031 fl/ft <br /> r <br /> r� <br /> r <br /> rEnvironeenng,Inc Project No 00-008 07 <br /> r Page 2 <br /> r <br />