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PUBLIC: HEALTH SERVICES <br /> SAN JOAQUIN COUNTY =: c <br /> ENVIRONMENTAL HEALTH DIVISION a <br /> Ernest M. Fujimoto, M.D., M.P.H., Acting Health Officer <br /> 445 N. San Joaquin Street • P. O. Box 388 • Stockton, C���g P209/468-3420 '(\\\\�"`.�.//;;;;�//"////Ii <br /> BRETT HUNTER MAM JUN 141995 <br /> CHEVRON USA PRODUCTS CO <br /> P O BOX 5004 <br /> SAN RAMON CA 94583-0804 <br /> RE: Chevron #9-4054 SITE CODE : 1780 <br /> 2103 Country Club Blvd <br /> Stockton, CA 95201 <br /> PHS-EHD has reviewed recently submitted correspondence and the <br /> report of MW-8 and MW-9 installations and has the following <br /> comments . <br /> The deepest soil sample analyzed from MW-8 was at 19 feet below <br /> ground surface ( ' bgs) . Field screening data indicated that the <br /> soil sample from MW-8 at 19' bgs had a "pid" reading of 421 ppm. <br /> Laboratory analytical data confirmed the presence of petroleum <br /> constituents in this sample . The soil sample from MW-8 at 24' <br /> bgs that was not analyzed had a "pid" reading of 143 ppm. No <br /> "pid" or analytical data is available for the soil sample at MW-8 <br /> at 29' bgs. With this incomplete data, PHS-EHD cannot accept <br /> your conclusion that the "lateral and vertical definition of soil <br /> contamination to the south has been achieved. " <br /> In order to define the lateral and vertical limits of the soil <br /> plume on or offsite, PHS-EHD will require valid laboratory data <br /> that supports your conclusions . Further investigation and <br /> delineation of contaminated soils is required to the south, west, <br /> and areas directly north/northwest of the site. <br /> Many private drinking water wells are located in this <br /> unincorporated area and their location, construction details, and <br /> water quality issues are still unresolved. A concise well survey, <br /> complete with water sample data, is required prior to any <br /> remediation plan approval . <br /> High levels of groundwater contamination and relatively low <br /> levels of shallow soil contamination suggest that deeper soil <br /> layers well into the saturated zone may be contributing to the <br /> groundwater contamination. These deeper soil formations will need <br /> to be analyzed in order to verify the vertical extent of the <br /> plume . Please ensure that your consultant and laboratory are <br /> capable of collecting and analyzing saturated soils from these <br /> depths . PHS-EHD will consider two consecutive five foot soil <br /> samples that are non detect at approved detection limits as <br /> evidence for vertical delineation. <br /> A Division of San Joaquin County Health Care Services <br />