SITE INFORMATION AND CORRESPONDENCE CASE 1

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PUBLIC HtALTH SERVICES SAN JOAQUIN COUNTY F" 1 ENVIRONMENTAL HEALTH DIVISION , Karen Furst, M.D., M.P.H., Health Officer 304 East Weber Avenue, Third Floor • Stockton, CA 9520 ►, 4` FOR� 209/468-3420 f PAT O'ROURKE BANK OF STOCKTON APR 141999 P O BOX 1110 STOCKTON CA 95201 Re: Western Lift/Cutter Lumber SITE CODE: 1087 3430 South EI Dorado Street Stockton, CA 95206 San Joaquin County Public Health Services, Environmental Health Division (PHS/EHD) is the lead agency providing the oversight of the investigation and cleanup of releases from underground storage tanks (UST's) within San Joaquin County. PHS/EHD has a contract with California State Water Resources Control Board to conduct an underground storage tank program. The above referenced site was placed in the PHS/EHD Local Oversight Program (LOP) in August 1991. On June 6, 1991 three UST's were removed under PHS/EHD permit and inspection. Soil sample results documented a gasoline release and the tank field was overexcavated to approximately 30 feet below ground surface (bgs). Due to the depth of the soil contamination and its close proximity to groundwater, a groundwater investigation was performed to further define the extent of the unauthorized release. Soil samples taken prior to monitoring well (MW) construction and groundwater sample results indicate a localized low concentration groundwater plume in this area of the facility. In June of 1996 another area of gasoline contamination was identified approximately 400 feet north of the 3 former UST's removed in 1991. Bank of Stockton research discovered information of a former Union Oil 1000 gallon UST at this location of the facility. In March of 1998, seven MW's were installed in the area of the former Union Oil UST. Six MW's were completed and screened in the zone of first water and one (MW-8A) was completed and screened approximately 50 feet below first water. All wells have evidenced gasoline contamination, with declining trends, and MW-7 remains the most contaminated well. Geo-Phase Environmental prepared and submitted a Quarterly Monitoring Report dated January 20, 1999 which contains groundwater analytical results from these seven wells for the last four Quarters. The analytical results from the six MW's screened in first water indicated the plume has been defined in the water above 45 feet bgs laterally with the exception of its western boundary. Groundwater from MW-8A has a Benzene concentration of 2 parts per billion, which is above the Maximum Contaminant Level (MCL) for public drinking water and the vertical distribution remains undefined. The lateral and vertical extent of gasoline contamination 45 feet bgs at this site has not been defined. You are directed A Division of San Joaquin County Health Care Services