ARCHIVED REPORTS XR0001830 - Laserfiche WebLink

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—.3 Local Local Groundwater Flow Direction and Gradient Thegroundwater suface undulates slightly but has a gentle slope toward SSOW with a gradient of 0 00I (Figure 4) This flow direction and gradient are consistent with published groundwater data from the City of Lodi(Environmental Forensic Investigations, Inc, 2002)and San Joaquin County Department of Public Works(2000)groundwater surface elevations for the North San Joaquin Water Conservation District 3.4 Petroleum Hydrocarbon Groundwater Plume The areal or horizontal extent of the petroleum hydrocarbon groundwater plume at the site extended throughout the site All monitoring wells except MW-4 had reportable concentrations of petroleum hydrocarbons Significant concentrations of TPH-gasoline and benzene were present in well MW-1, 2, 3, and 6 at concentrations above maximum contaminant levels(MCLs) Minor concentrations of 1,2-DCA and 1,2-EDB above MCLS were reported in monitoring wells MW 1 and 3_ MTBE was reported to be present at low concentrations in MW-2 and MW-3 A review of past groundwater petroleum:hydrocarbon concentrations was made and included in the tabulations presented in Table 4 No horizontal limit of the petroleum hydrocarbon contamination plume has been identified to date The past maximum areal extent of the groundwater petroleum hydrocarbon plume as determined from previous work suggests the site to has had a minimum areal extent of approximately 200 by 225 feet(45,000 square feet) The horizontal extent of petroleum hydrocarbon I contamination groundwater plume for this reporting period is estimated to be at least 13,600 square feet This minimum documented groundwater plume extent is about 1/3 the size of the previous monitoring event • The extent of the release is currently unknown and undocumented in both the vertical and horizontal extent 1t is unclear at this time if the site poses a threat to local water supplies 4.0 PLANNED FUTURE WORK The next planned operation for this site will include additional Quarterly Status Report(QSR)and quarterly monitoring report(QMR)for the period ending June 30, 2004 A sensitive receptor survey of the nearby water supply wells will be completed during the 2'and 3'quarters of 2004 • Main\D\Environtmnta n=rTe=co\ReporCM33104QMR wpd 5