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r w <br /> PUBLIC H15ALTH SERVICES <br /> SAN JOAQUIN COUNTY r.;' <br /> 'A <br /> ENVIRONMENTAL HEALTH DIVISION <br /> 1 . <br /> Karen Furst, M.D., M.P.H., Health Officer <br /> 304 East Weber Avenue, Third Floor • Stockton, CA 95202 `'FOR`' <br /> 209/468-3420 <br /> 904 <br /> RE: SITE CODE <br /> S� <br /> San Joaquin County Public Health Services Environmental Health Division (PHS/EHD) has reviewed the <br /> work plan for the above referenced site including recent and historic quarterly ground water sampling data <br /> sets submitted to this office. <br /> Fuel additives may be present in the subsurface environment at this site. Data generated to date is <br /> inconclusive for the presence or absence of blending agents (preliminary analytical data indicates the <br /> presence of MTBE, subsequent data indicates MTBE is not present). You are required to analyze all water <br /> and selected soil samples for Tertiary Butanol, MTBE, DIPE,ETBE, and TAME employing EPA 8260 for <br /> all samples until further written notice from this office (see CVRWQCB and PHS/EHD attachments <br /> regarding these analytes). All wells shall be sampled the same day. Selected soil samples shall include at a <br /> minimum the historic low and high groundwater elevation equivalent and the current capillary fringe. <br /> Traditional TPH as gasoline and BTEX analyses are also required. Additional soil and ground water <br /> samples may be required to be analyzed as directed and at the discretion of the PHS/EHD site inspector. <br /> A workplan prepared by dated April 1997 has been reviewed considering the most recent <br /> quarterly ground water monitoring events (August 12, 1997 sampling data received by PHS/EHD on <br /> October 6, 1997) and an addendum is required. Additional boreholes shall be distributed at this site which <br /> employ the findings of the comprehensive site hydrogeologic cross sections. At least four boreholes shall <br /> be continuous cores. All continuous cores shall be collected in approved sampling sleeves. These <br /> boreholes shall be appropriately logged and employed to further define any plume which may have <br /> originated from the former or current use practices at this site. The workplan shall be revised to consider <br /> historic low and high groundwater elevations in the definition of the vertical aspect of contaminant <br /> distribution at this site. San Joaquin County Flood Control records indicate that ground water in this area <br /> of Stockton may have been in excess of 110 feet below surface grade during the fall of 1978. Conventional <br /> monitoring well networks existing and proposed for this Underground Fuel Tank (UST) leak site may be <br /> insufficient to properly locate and define the extent or existence of Petroleum Hyrocarbon /Fuel Additive <br /> plumes as evidenced by the vertical and horizontal variations of contamination observed at this site. <br /> Boreholes completed as monitoring wells must be placed at the site with appropriate discrete screen <br /> intervals based on site specific findings(preferential pathways/contaminant loading)not arbitrary depths as <br /> proposed (each borehole may require more than one well completion). Well screen intervals shall not <br /> exceed 20' in total length. Well screen and filter pack construction shall not act as a vertical or horizontal <br /> contaminant transport mechanism. Preferably, monitor well screened intervals shall not exceed the height <br /> of the hydrogeologic interval under investigation (preferential pathway). Once vertical characterization is <br /> I <br /> A Division of San Joaquin County Health Care Services <br />