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1 Atlantic Richfield Company 2 ARCO 5450, 1617 West Fremont Street,Stockton,CA April 10 2002 • 0.044 mg/kg, respectively, at approximately 11.5 feet below ground surface (bgs). TPHg was not detected at 11.5 feet bgs (BC, 1997). On July 30, 1996, BC drilled and installed one 2-inch groundwater monitoring well (MW-1) near the southwestern dispenser island to a depth of 25 feet bgs. Laboratory analysis reported total xylenes in all three soil samples analyzed with concentrations ranging from 0.0064 mg/kg to 0.0089 mg/kg. No other hydrocarbons were detected. Lithology encountered during drilling included interbedded silty sands to approximately 16 feet bgs and saturated clayey-silty sand from approximately 16 feet to 25 feet bgs (BC, 1997). Brown and Caldwell sampled well MW-1 on July 30, 1996, November 15, 1996, and March 19, 1997. Laboratory analysis reported concentrations of methyl tert-butyl ether (MtBE) of 35 micrograms per liter (gg/L), 8 µg/L, and 19 µg/L, respectively, during those sampling events. TPHg and BTEX were not detected in any of the three sampling events. Depth to groundwater ranged from 8.89 feet to 12.37 feet bgs (BC, 1997). On August 4, 1997, the California Regional Water Quality Control Board—Central Valley Region (CRWQCB-CVR) issued the site "No Further Action Required" status (CRWQCB-CVR, 1997). Between 1997 and 1999, well MW-1 was abandoned. A well abandonment report was not provided to SECOR, however, on November 12, 2001, SECOR personnel visually confirmed the abandonment of well MW-1. On November 24, 1999, Delta Environmental Consultants, Incorporated (Delta) performed oversight and soil sampling during facility product piping and dispenser upgrade activities. Ten soil samples were collected beneath the product piping lines and eight soil samples were collected beneath the product dispensers. In soil sample PL-9- 5.5 laboratory analysis reported concentrations of toluene, ethyl benzene, xylenes, and MtBE of 0.0436 mg/kg, 0.0124 mg/kg, 0.0925 mg/kg, and 0.201 mg/kg, respectively. Xylenes concentrations of 0.0448 and 0.0109 were also reported in soil samples PL44.0 and DP8-4.5, respectively. PL-9 and PL-4 samples were taken from east of the dispensers. Hydrocarbons or volatile organic compounds (VOCs) were not detected in any other soil sample collected (Delta, 2000). ASSESSMENT ACTIVITIES AND FINDINGS On February 21, 2002, three soil borings (SB-1, SB-2, and SB-3) were completed at the site by West Hazmat Drilling of Rancho Cordova, California. The soil borings were advanced to a depth of approximately 20 feet bgs. Boring logs showing the subsurface lithology of each boring is included as Attachment B. The findings of this assessment are discussed below: 77BP.43323.00.02301site assessment.doc h