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S ECOR <br /> QUARTERLY MONITORING AND <br /> REMEDIAL PERFORMANCE SUMMARY REPORT <br /> Second Quarter 2005 <br /> 76 (Former BP) Service Station No. 11195 <br /> 16500 South 1-5 <br /> Lathrop, California <br /> City/County ID#; Lathrop <br /> County: San Joaquin <br /> SITE DESCRIPTION <br /> A retail gasoline outlet has been located at the subject site since at least 1983. BP Oil <br /> Company (BP) acquired the site from Mobil Oil Corporation in 1989. The site was then <br /> sold from BP to Tosco Corporation (Tosco) in 1994. Current site features include two <br /> 12,000-gallon, double-walled, underground storage tanks (USTs), two dispenser islands, <br /> product lines, a canopy, and a station building. <br /> PREVIOUS ASSESSMENT <br /> `= Five on-site groundwater monitoring wells (MW-1 through MW-5) were installed in <br /> December 1992. Soil samples collected from the well borings contained petroleum <br /> hydrocarbons at concentrations of up to 120 parts per million (ppm) of total petroleum <br /> hydrocarbons as gasoline (TPHg), and 16 ppm of benzene. The initial groundwater <br /> samples collected from wells MW-3 and MW-4 contained concentrations of up to 10,000 <br /> parts per billion (ppb) of TPHg. Quarterly groundwater monitoring and sampling activities <br /> were subsequently initiated at the site. <br /> Two additional wells (MW-6 on-site and MW-7 off-site) were installed in September 1993. <br /> Soil samples collected at a depth of 6 feet below ground surface (bgs) did not contain <br /> petroleum hydrocarbons. <br /> r <br /> One 550-gallon fiberglass waste oil UST and an associated remote fill line were removed <br /> from beneath the site in 1997. Soil samples collected from beneath the waste oil UST ; <br /> excavation (10 feet bgs) and beneath the remote fill line (3 feet bgs) did not contain <br /> detectable concentrations of petroleum hydrocarbons (GeoStrategies, Waste Oil UST and <br /> Remote Fill Line Soil Sampling Report, dated August 6, 1997). <br /> In July 1998, an abandoned water well, located north of the former UST pit adjacent to <br /> Louise Avenue, was properly destroyed. The well was destroyed by perforating the steel <br /> casing, and grouting the well with neat cement placed by the use of a grout pump and <br /> tremmie pipe. The well destruction was permitted and observed by San Joaquin County <br /> Environmental Health Department (SJCEHD). <br /> 1:1ConocoPhillipslRetail Sites1111951QSR&QRPS 2005/11195 QSR&QRPS 2Q05.doc <br />