SITE INFORMATION AND CORRESPONDENCE

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.x San Joaquin County Environmental Health Department DIRECTOR 5.. p� Donna Heran, REHS <- y� 600 East Main Street Stockton, California 95202-3029 PROGRAM COORDINATORS v { Margaret Lagorlo, REHS • Robert McClellan,REHS `P Website: www.s ov.or /ehd Jeff Garruesco,RENS, RDI 4�Ikotiza �9 Kasey Foley, REHS Phone: (209) 468-3420 Fax: (209)464-0138 November 4, 2009 Walter Spargue Pacific Convenience & Fuels 22026 68t'' Avenue South Kent, WA 98032 Subject: Former BP Station # 11191 1469 E. Hammer Lane Stockton, CA 95210 San Joaquin County Environmental Health Department (EHD) is the lead agency providing the oversight of the investigation and cleanup of releases from underground storage tanks (USTs) within San Joaquin County. The above subject site was placed in the EHD Local Oversight Program (LOP) in June 1993 due to soil contamination found during a site assessment in December 1992. In February 1998, four USTs were removed from this site and new USTs were installed. The analytical results for soil samples collected in the former tank locations and the piping trenches evidenced gasoline, diesel, TBA, and MTBE contamination. A limited amount of contaminated soil was excavated from the UST and piping locations and disposed of off-site. Soil samples were collected for analyses from the excavated areas and contaminant concentrations that remained in place are as high as the following: 1800 parts per million (ppm) TPH-gasoline, 12 ppm TPH-diesel, 12 ppm TBA, 99 ppm xylene, 10 ppm ethylbenzene, and 4.9 ppm MTBE. Due to the high concentrations of residual gasoline contamination, additional soil and ground water assessment was required. In December 2001, monitoring wells MW1 through MW4 were installed on-site to a total depth of 60 feet below ground surface (bgs). Ground water sample results from MW 1 through MW4 evidenced high levels of TPH-gasoline and MTBE contamination which have decreased since 2005. On March 4, 2003, monitoring wells MW6 and MW7 were installed off-site (screened from 30 to 60 feet across first water). The ground water sample results from MW6 and MW7 have been generally below detection limits. These wells are located cross-gradient of groundwater flow. On March 5, 2003, monitoring well MW5 was drilled on-site, northwest of the former USTs to a total depth of 90 feet bgs, then backfilled with sand to 70 feet bgs. The well casing was set at 70- feet and screened from 65 to 70 feet bgs. The ground water sample results from this deeper screened well have evidenced high concentrations of TPH-gasoline and MTBE concentrations that have not decreased.