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QUARTERLY GROUND WATER MONITORING REPORT <br /> First Quarter of 1992 <br /> 4491 West Durham Ferry Road <br /> Delta Projwt No 40-91-732 <br /> Page 2 <br /> 2.2 Site Background <br /> Ms Stella Ruiz purchased the property from Mr Eugene Heitt in May 1986 In February 1988, <br /> Petro Check removed two 1,000-gallon underground storage tanks which had contained leaded and unleaded <br /> ' gasoline Chemical analysis of soli samples collected from the tank excavation indicated that further <br /> investigation was required. <br /> On May 27, 1988, monitoring well MW-1 was installed north of the tank locations by Water Works <br /> ' A ground water sample was collected on June 13, 1988, from monitoring well MW-1 and analyzed for <br /> petroleum constituents The results of the chemical analysts indicated concentrations of 16, 16 5, and <br /> 1 247 parts per billion (ppb) for benzene, toluene, and total petroleum hydrocarbons, respectively Further <br /> investigation was requested by the County of San Joaquin in a letter dated June 11, 1991 <br /> ' On July 26, 1991, Delta submitted a Phase 1 Hydrogeologic Investigation Work Plan to Ms Eleanor Ratliff <br /> of the County of San Joaquin(the County) to characterize the presence of petroleum hydrocarbons at the site <br /> On August 28, 1991, Delta installed two monitoring wells MW-2 and MW-3 On September 4, 1991, <br /> ground water samples were collected from morutoring wells MW-1, MW-2 and MW-3 and were sent to a <br /> California-certified laboratory to be analyzed for the presence of petroleum hydrocarbon constituents <br /> On November 14, 1991, Delta submitted a Phase I HydrogeoIogic Investigation Report to the county <br /> characterizing the presence of petroleum hydrocarbons at the site <br /> 2.3—Regional Hydrogeol� <br /> A regional map showing the ground water elevation contours for the unconfined aquifer for spring 1989, <br /> ' prepared by the San Joaquin County Flood Control and Water Conservation District, shows the direction <br /> of ground water flow is towards the north or northeast The direction of ground water flow based on the <br /> ' regional slope of the land surface is expected to be toward the northeast <br /> 1 <br /> RPT 116 HMB <br />