SITE INFORMATION AND CORRESPONDENCE

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Y Y PUBLIC F�EALTH SERVI 'ES SAN JOAQUIN COUNTY ENVIRONMENTAL HEALTH DIVISION 76 Karen Furst, M.D., M.P.H., Health Officer �. 304 East Weber Avenue,,Third Floor • Stockton, CA 95202 209/468-3420 CC_CT 1 6W7 GERALD THIEMANN i 327 BLOSSOM DRIVE RIPON CA 95366 Re: Thiemann's Service Site Code: 1479 106 Second Street, Ripon CA 95366 San Joaquin County Public Health Services, Environmental Health Division (PHS/EHD) has completed review of the "Monitoring Report Third Quarter 1997" dated October 1, 1997 and prepared by Smith Environmental Technologies. PHS/EHD has the following comments for your consideration and response. The analytical results from groundwater samples collected on July 9, 1997 indicate a continuing rise of concentrations of contaminants following the January 27, 1997 sampling event. The hydrologic condition of flooding which prevailed in January 1997, undoubtedly had some influence on the contaminant transport beneath the site. The site is located approximately 4,000"north of the Stanislaus River, and while surface flooding in the + vicinity of the site did not occur, the subsurface environment was surely affected. Between April and July 1997, there was an approximate two fold increase in contaminant concentrations observed in the groundwater, once again suggesting that the remaining soil contamination poses a threat to groundwater quality. As water is once again receding, the water table depth has decreased approximately 3.5 feet since April 1997, it is appropriate to move forward with the installation of vapor extraction and air sparge wells for feasibility testing. An important component of a corrective action plan, prepared pursuant to the Underground Storage Tank Regulations and Health and Safety Code, is feasibility analysis so that the most cost effective remedial alternative may be implemented to restore and protect the groundwater beneath the site from further degradation of water quality. In further review of site conditions, it has been noted that the vertical extent of the soil contamination has not been ascertained. The maximum depth of investigation in the area of the tank pit was 30 feet and the sample which was collected evidenced significant petroleum hydrocarbon contamination of up to 4,700 ppm total petroleum J hydrocarbon as gasoline. In addition to the proposed soil vapor extraction and air sparge wells, a work plan addendum shall be submitted which completes the vertical investigation of the contamination evidenced to date. PHS/EHD has been directed to request that groundwater samples undergo EPA Method 8260 analysis for oxygenates. While methyl tertiary butyl ether has not been detected using EPA Method 8020, additional octane boosting agents have been used which may have been a component of the gasoline used while the tanks were in j operation. ; PHS/EHD hopes that once active remedial efforts are undertaken that site closure conditions can be achieved. Please proceed with efforts to obtain pre-approval from the State Water Resources Control Board for the previously denied work and for the newly directed activities associated with the investigation of the vertical extent of the soil contamination. Please contact me at(209) 468-0337 if you have any questions or wish to discuss the site further. Donna Heran, REHS, Director /Environmental Health Division j 7-0 Mary Meays, Senior REHSI Margaret L gorio, REHS V Site Mitigation Unit Lead Senior cc: Elizabeth Thayer, CVRWQCB I cc: Ismael Jacabo, SWRCB Cleanup Unit cc: Jeanne Homsey, Smith Environmental A Division of San Joaquin County Health Care Services