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PUBLIC HL*ALTH S <br /> SAN JOAQUIN COUNTY A <br /> ENVIRONMENTAL HEALTH DIVISION <br /> Karen Furst, M.D., M.P.H., Health Officer <br /> 304 East Weber Avenue, Third Floor - Stockton, CA 95202 9``FOR�' <br /> 209/468-3420 <br /> RUSSELL CHAPIN <br /> CHAPIN BROTHERS INC APR 131999 <br /> 1203 N CARLTON AVENUE COPY STOCKTON CA 95203 <br /> Re: Chapin Brothers, Inc. SITE CODE: 1190 <br /> 1766 Monte Diablo <br /> Stockton, CA 95203 <br /> San Joaquin County Public Health Services, Environmental Health Division (PHS/EHD) <br /> is the lead agency providing the oversight of the investigation and cleanup of releases <br /> from underground storage tanks (UST's) within San Joaquin County. PHS/EHD has a <br /> contract with California State Water Resources Control Board to conduct an <br /> underground storage tank program. The above referenced site was placed in the <br /> PHS/EHD Local Oversight Program (LOP) in August 1991. <br /> On March 25, 1999 PHS/EHD met with you and your consultant, Advanced <br /> GeoEnvironmental, Inc. (AGE), to review the investigation and remedial activities for the <br /> above referenced site. We reviewed site history, findings from investigations, analytical <br /> results from monitoring events, and remedial action performed on site. <br /> In December 1990, a monitoring well (MW) was installed on site and groundwater <br /> contamination was documented; free phase gasoline was observed in the well (MW-1). <br /> In August 1993, 8 USTs were removed under PHD/EHD permit and inspection. Soil <br /> sample results documented a gasoline release and the tank field was overexcavated to <br /> approximately 15 feet below ground surface (bgs). Due to the depth of the soil <br /> contamination and its close proximity to groundwater, additional soil and groundwater <br /> sampling was performed to further define the extent of the unauthorized release. Soil <br /> and groundwater sample results taken prior to MW construction indicated the <br /> contaminant plume had migrated off site in a southwesterly direction. <br /> In August 1995, PHS/EHD approved your Corrective Action Plan to utilize vapor <br /> extraction for site remediation. At that time, groundwater was approximately 22 feet bgs <br /> and the vapor extraction system (VES) was engineered and designed accordingly. To <br /> date, 7 groundwater MWs have been installed: 2 on site and 5 off site. Groundwater is <br /> now approximately 10 feet bgs. Several vapor extraction and air sparging wells have <br /> been installed. The VES has reduced the contaminant load in the groundwater on site <br /> considerably, but has not reduced the concentration in groundwater off site in the vicinity <br /> of the downgradient MW-3. <br /> PHS/EHD recommends continued on site remedial measures, soil vapor extraction and <br /> air sparging, to further reduce groundwater contaminant concentrations on site and <br /> reduce the amount of off site migration downgradient to the southwest in the vicinity of <br /> MW-3 and MW-5. <br /> A Division of San Joaquin County Health Care Services <br />