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benzene at concentrations of 7 5 ppb, toluene at concentrations of 3 1 ppb, and xylenes at <br /> concentrations of 190 ppb Analytical results are summarized in Table 2 <br /> In April 1994, approximately 54,000 gallons of groundwater was removed from the open excavation <br /> pit using vacuum pump equipped trucks Work was performed by Roto-Rooter Sewer Service and <br /> Star Sewer Service under the direct supervision of RESNA personnel The purged water was <br /> transported to the Stockton Regional Wastewater Control Facility and discharged into the sanitary <br /> sewer system under an approved City of Stockton Department of Municipal Utilities discharge request <br /> Waste hauler manifest forms are contained in Appendix D <br /> Subsequent to groundwater disposal, groundwater was allowed to flow into the excavation pit and <br /> recover to its prepurge level A discrete groundwater sample was collected, placed on ice and <br /> transported under chain-of-custody documentation to Argon Laboratories The sample was analyzed <br /> for TPH& TPHd, and BTEX No petroleum hydrocarbons were detected in the sample Groundwater <br /> analytical results are summarized in Table 2 <br /> 5.0 EXISTING CONDITIONS <br /> 5_1 Soil Conditions <br /> Soils encountered beneath the project site consist primarily of lean to fat clay to approximately 415 <br /> feet below grade Apparent interbedded sand and silt lenses were noted at various depths in soil <br /> borings MW-1, MW-3, and MW-4 Silt was encountered in soil boring MW-2 at approximately 41 <br /> feet below grade,the maximum depth explored <br /> Confirmation soil borings were not advanced following soil remediation activities at the site based on <br /> the nondetectable results obtained from the soil excavation bottom and sidewalls in November 1993 <br /> Soil samples were not collected during the installation of MW-1R in January 1995 <br /> 5_2 Groundwater Conditions <br /> Shallow groundwater beneath the site is encountered at approximately 12 feet below grade and <br /> generally flows to the southeast with a gradient of 0 011 ft/ft, or approximately 58 fl/mde The <br /> groundwater gradient measured on February 23, 1996 is depicted on Figure 3 <br /> Results from the most recent groundwater sampling event indicate that TPHg, TPHd, and BTEX are <br /> below method detection limits in wells MW-1R through MW4 These results are consistent with <br /> historical data(Table 2) <br /> w 194338klosm cim 6 <br /> 1 <br /> Sian <br />