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<br /> S E C 0 R
<br /> QUARTERLY SUMMARY REPORT
<br /> I
<br /> �) THIRD QUARTER 2003
<br /> 76 (former BP) Service Station #11192 u
<br /> 1403 West Country Club Boulevard, Stockton, California 3'
<br /> t
<br /> City/County ID# Stockton %
<br /> County San Joaquin +
<br /> BACKGROUND
<br /> The site is located at 1403 West Country Club Boulevard in Stockton, California and is an operating
<br /> 76 service station The operating facility consists of two gasoline USTs, one waste oil UST
<br /> (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 four
<br /> 2,000-gallon) were installed in 1976, and were removed in 1991 During tank removal activities, well
<br /> MW-2 was destroyed Also in 1991, the three current 10,000-gallon gasoline LISTS were installed A
<br /> soil gas survey was performed in 1989 A well survey was performed in 1989 that indicated a water
<br /> supply well is located 1,100 feet northwest from the site, and a private well is located 900 feet from
<br /> the site Seven groundwater monitoring wells and two vapor extraction wells were installed at the
<br /> site between 1990 and 1991 A hydropunch study, including a soil vapor extraction test, was a
<br /> 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 16,
<br /> • 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 of
<br /> the eight events, prior to removal of the water from the site The estimated mass of methyl tertiary
<br /> butyl ether (MtBE) removed with the extracted groundwater was calculated using the average MtBE
<br /> concentration from the pre-purging and post-purging grab groundwater samples for each purging
<br /> event Based on these average concentrations, an estimated total of 26 63 pounds of MtBE were
<br /> removed from the site during the eight purging events between November 16, 2000 and January 2,
<br /> 2001 The weekly purging was discontinued after the eight week period approved by the PHS-EHD
<br /> In April of 2001, GR conducted a subsurface investigation at the site involving eight geoprobe soil
<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 (ND) for Total Petroleum
<br /> Hydrocarbons as gasoline (TPHg), benzene, toluene, ethylbenzene, xylenes (BTEX), MtBE, ethanol,
<br /> tert-butyl alcohol (TBA), di-isopropyl ether (DIPE), ethyl tert-butyl ether (ETRE), 1,2-dichloroethane
<br /> (1,2 DCA) tert-amyl methyl ether (TAME) and ethylene dibromide (EDB) Groundwater samples
<br /> from the Geoprobes and were reported as ND for all analytes in samples B-3, B-5, B-6, B-7 and B-8
<br /> Sample B-1 contained MtBE at 90 parts per billion (ppb) and DIPE at 2 8 ppb Sample B-2
<br /> contained only MtBE at 15 ppb Sample B-4 contained MtBE at 11 ppb Sample CPT-1, collected
<br /> at 75 feet below ground surface(bgs), contained MtBE at 120 ppb and 1,2-DCA at 23 ppb
<br /> Also in April of 2001, GR conducted a well search and Sensitive Receptor Survey (SRS) in the
<br /> vicinity of the subject site The well search was conducted within a '/2-mile radius around the site
<br /> Based on the available data supplied by the California Department of Water Resources (DWR), three
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