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Van Buskirk Park Golf Course TL 394-0074-01 . November 23, 1994 Page 2 2.0 BACKGROUND Twining understands that a 550-gallon gasoline underground storage tank (UST) was removed from the site in April 1991 and that analysis of a soil sample collected from four feet below site grade (BSG)in the vicinity of the former dispenser detected 350 milligrams per kilogram (mg/kg) TPH-G and 7,200 mg/kg TPH-D. Twining also understands that a 1,000-gallon diesel UST was removed in January 1994. Analysis of a soil sample collected from 11 feet BSG at the west end of the excavation detected 135 mg/kg TPH-D,435 mg/kg TPH-G, 5.8 mg/kg benzene, 29 mg/kg toluene, 8.2 mg/kg ethylbenzene, and 44 mg/kg total xylenes. Twining installed three groundwater monitoring wells at the site in June of 1994 (Twining, 1994A). Six soil samples were analyzed in the laboratory for TPH--D, TPH-G, and BTEX. Analysis of four of the soil samples (MW1-10, MW2-10, MW2-15, and MW3-10) did not detect concentrations of TPH-D, TPH-G, or BTEX at or above the method detection limits. Analysis of the other two soil samples (MW1-15 and MW3-15) did not detect TPH-G or BTEX concentrations at or above the method detection limits, but did detect TPH-D at the method detection limit of 1 mg/kg. A groundwater sample was collected from each well on June 22, 1994. The samples were analyzed in the laboratory for TPH-D, TPH-G, and BTEX. Groundwater samples MW1 and MW2 did not contain detectable concentrations of TPH-D, TPH-G, or BTEX. Analysis of groundwater sample MW3 did not detect concentrations of TPH-D, toluene, or ethylbenzene above method detection limits, but did detect 55 micrograms per liter (ug/L) TPH-G, 1.4 ug/L benzene, and 1.7 ug/L total xylenes. 3.0 FIELD PROCEDURES Field activities are summarized in the following subsections. 3.1 Groundwater Sampling: Groundwater monitoring wells MW1, MW2, and MW3 were sampled on October 27, 1994. Three to rive well casing volumes were purged prior to sampling. Purge water was retained in sealed DOT-approved 55--gallon drums. Purging continued until relatively clear water was discharged and the pH, conductivity, and temperature stabilized. Groundwater sampling logs are presented in Attachment I. Mr. Steve Sasson of the San Joaquin County Public Health Services Agency/Environmental Health Division was on site during groundwater sampling. 3.2 Groundwater Analysis • Groundwater samples collected during this investigation were submitted to Twining's California- certified analytical laboratory in Fresno, California. Groundwater samples were analyzed for