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SEIC0R
<br /> QUARTERLY SUMMARY REPORT
<br /> THIRD QUARTER 2004
<br /> 76 (former BP) Service Station #11192
<br /> 1403 West Country Club Boulevard, Stockton, California
<br /> City/County ID # Stockton
<br /> County San Joaquin
<br /> PREVIOUS ASSESSMENT
<br /> The site is located at 1403 West Country Club Boulevard in Stockton, California and is an
<br /> operating 76 service station The operating facility consists of two gasoline USTs, one waste oil
<br /> UST (operated by others), associated product lines, and four dispenser islands
<br /> Based on information supplied by BP and Tosco, the previous USTs (three 10,000-gallon and
<br /> four 2,000-gallon) were installed in 1976, and were removed in 1991 During tank removal
<br /> activities, well MW-2 was destroyed Also in 1991, the three current 10,000-gallon gasoline USTs
<br /> were installed A sod gas survey was performed in 1989 A well survey was performed in 1989
<br /> that indicated a water supply well is located 1,100 feet northwest from the site, and a private well
<br /> is located 900 feet from the site Seven groundwater monitoring wells and two vapor extraction
<br /> wells were installed at the site between 1990 and 1991 A hydropunch study, including a soil
<br /> vapor extraction test, was conducted in 1992 Four soil borings were advanced in 1994
<br /> . Eight weekly groundwater extraction events occurred between November 16, 2000 and January 2,
<br /> 2001 During these events, approximately 2,400 to 3,800 gallons of groundwater per event were
<br /> removed from monitoring well MW-3 by Onyx Industrial Services (Onyx) of Benicia, California In
<br /> addition, approximately 600 gallons of groundwater were removed from well MW-7 on November
<br /> 16, 2000 The groundwater was extracted directly from the wells into an Onyx vacuum truck and
<br /> transported to the Tosco Refinery in Rodeo, California, for disposal A total of approximately 27,200
<br /> gallons of groundwater were removed from the site during the eight weekly extraction events
<br /> Groundwater samples were collected from well MW-3 prior to and following each of the eight
<br /> extraction events A water sample was also collected from the purged groundwater during each
<br /> of the eight events, prior to removal of the water from the site The estimated mass of methyl
<br /> tertiary butyl ether (MtBE) removed with the extracted groundwater was calculated using the
<br /> average MtBE concentration from the pre-purging and post-purging grab groundwater samples
<br /> for each purging event Based on these average concentrations, an estimated total of 26 63
<br /> pounds of MtBE were removed from the site during the eight purging events between November
<br /> 16, 2000 and January 2, 2001 The weekly purging was discontinued after the eight week period
<br /> approved by the PHS-EHD
<br /> In April of 2001, GR conducted a subsurface investigation at the site involving eight geoprobe sod
<br /> borings (six offsite and two onsite) and one onsite CPT probe Selected soil samples collected
<br /> during probing and CPT were reported by the laboratory as not detected (N D) for Total Petroleum
<br /> Hydrocarbons as gasoline (TPHg), benzene, toluene, ethylbenzene, xylenes (BTEX), MtBE,
<br /> ethanol, tert-butyl alcohol (TBA), di-isopropyl ether (DIPE), ethyl tert-butyl ether (ETBE),
<br /> 1,2-dichloroethane (1,2 DCA) tert-amyl methyl ether (TAME) and ethylene dibromide (EDB)
<br /> Groundwater samples from the Geoprobes and were reported as ND for all analytes in samples
<br /> B-3, B-5, B-6, B-7 and B-8 Sample B-1 contained MtBE at 90 parts per billion (ppb) and DIPE at
<br /> 2 8 ppb Sample B-2 contained only MtBE at 15 ppb Sample B-4 contained MtBE at 11 ppb
<br /> Sample CPT-1, collected at 75 feet below ground surface (bgs), contained MtBE at 120 ppb and
<br /> 1,2-DCA at 23 ppb
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