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QUARTERLY GROUND WATER MONITORING REPORT <br /> Second Quarter of 1992 <br /> 4491 West Durham Ferry Road <br /> Delta Project No 40-91-732 <br /> Page 2 <br />' 2.2 Site Back round <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 <br /> unleaded gasoline Chemical analysis of soil samples collected from the tank excavation indicated that <br /> further 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 analysis indicated concentrations of 1 6, 16 5, and <br /> 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 /> 1 <br /> On July 26, 1991, Delta submitted a Phase I Hydrogeologic Investigation Work Plan to Ms <br /> Eleanor Ratliff of the County of San Joaquin (the County) to characterize the presence of petroleum <br /> hydrocarbons at the site On August 28, 1991, Delta installed monitoring wells MW-2 and iVW-3 On <br />' September 4, 1991, ground water samples were collected from monitoring wells MW-1, 1VW-2 and <br /> MW-3 and were sent to a California-certified laboratory to be analyzed for the presence of petroleum <br />' hydrocarbon constituents On November 14, 1991, Delta submitted a Phase I Hydrogeologic <br /> Investigation Report to the county characterizing the presence of petroleum hydrocarbons at the site On <br />' May 20, 1992, Delta submitted a Quarterly Ground Water Monitoring Report for the first <br /> quarter of 1992, to the County characterizing the presence of petroleum hydrocarbons in the ground water <br />' beneath the site <br />' 2.3 Regional Hydrogeology <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 /> RPT029 TA <br />