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• Well Installation and Soil Boring Report-Tosco (former Unocal) Service Station#6981, Stockton, CA <br /> November 15, 1999 <br /> Waste Disposal <br /> Approximately seventons of non-hazardous solid waste was accepted fordisposal atAllied Waste Industries, <br /> Inc 's Forward Landfill, in Manteca, CA, for disposal A copy of Allied's acceptance letter is included in <br /> Appendix F On August 27, 1999, Manley and Sons Trucking, Inc transported 6 85 tons of soil to the <br /> Forward The Manley disposal confirmation is also included in Appendix F <br /> Approximately 500 gallons of liquid waste (cleaning water generated during the drilling activities and <br /> groundwater generated during well development)were removed by GR to Tosco's refinery in Rodeo, CA <br /> for treatment and disposal on August 21, 1999 <br /> SUMMARY AND CONCLUSIONS <br /> Gettler-Ryan, Inc, offers the following summary and conclusions <br /> 1 Groundwater monitoring well MW-15 was installed to replace abandoned monitoring wells MW-12 <br /> and MW-13 <br /> 2 Concentrations of remaining petroleum hydrocarbons in soil at the site are very low to ND at all <br /> boring locations with the exception of boring VW-7 Boring VW-7 is located adjacent to vapor <br /> • extraction well VW-2 in which the highest residual hydrocarbon concentrations in soil were <br /> detected during the initial groundwater and soil investigation <br /> 3 The highest dissolved MtBE concentration (510 ppb) is found in well VW-7 which is located <br /> closest to the source area for hydrocarbon impact The dissolved MtBE concentration in the <br /> newly installed down-gradient well MW-15 was 2 0 ppb <br /> 4 TPHg, benzene, and MtBE concentrations were ND in all soil samples at the maximum depth <br /> sampled This depth ranged from 39 feet bgs outside the source area in MW-14 and MW-15 to <br /> 86 feet bgs at the source area in VW-7 The vertical extent of contamination in soil has, therefore, <br /> been defined <br /> 5 The three new groundwater monitoring wells, MW-14, MW-15, and MW-16, are appropriately <br /> screened to intersect the current groundwater level Concentrations of target compounds detected <br /> in monitoring wells MW-14 and MW-16 correlate well with the latest quarterly data gathered from <br /> nearby deep-screened and drowned monitoring wells MW-7 (near MW-14) and MW-2 (near <br /> MW-16) <br /> 6 Hydrocarbon impact to soil and groundwater gas been delineated both vertically and horizontally <br /> Impact appears to be limited to the vicinity of the dispenser islands to a depth of approximately <br /> 86 feet bgs <br /> • <br /> 140124 05 5 <br />