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-r <br /> cou <br /> PUBLIC ?1EALTH SER) CES <br /> SAN JOAQUIN COUNTY <br /> ENVIRONMENTAL HEALTH DMSION <br /> Karen Furst, M.D., M.P.H., Health Officer <br /> 304 East Weber Avenue, Third Floor • Stockton, CA 9520toFly ""oR <br /> 209/468-3420 <br /> ALEX PEREZ <br /> SHELL OIL PRODUCTS COMPANY MAY 2 8 1998 <br /> PO BOX 8080 <br /> MARTINEZ CA 94553 <br /> RE: SHELL SERVICE STATION SITE CODE: 506186 <br /> 341 MAIN STREET <br /> RIPON CA <br /> As a result of reviewing site specific data from the most recent groundwater and soil sampling events for <br /> the above referenced site, San Joaquin County Public Health Services Environmental Health Division <br /> (PHS/EHD)provides the following comments and directives. <br /> Elevated concentrations of Methyl tertiary butyl ether (MTBE) 97,000 ug/L, and Methanol 31,000 ug/L <br /> were confirmed by a state certified laboratory in groundwater samples taken from an area near the existing <br /> and former pump island/dispensers. With regard to ground water contamination it is apparent that MTBE <br /> concentrations are significant and have likely migrated off site realizing that the property lines are less than <br /> 30 feet south and 60 feet west from MW-I which is impacted by fuel hydrocarbon constituents. <br /> Of significant interest to PHS/EHD is the boring log for this bore hole/well which display the geologists <br /> certified observations revealing the presence of a predominantly Sandy,medium to coarse grain, very high <br /> estimated permeability saturated zone. It is also interesting to note that Benzene, Toluene, Ethylbenzene, <br /> Xylenes and Total Petroleum Hydrocarbons(TPH)as Gasoline have not been detected in MW-I which has <br /> documented high concentrations of MTBE in groundwater and soil which further suggests that MTBE <br /> migration is rapid in this hydrogeologic setting. <br /> PHS/EHD considers the concentrations of MTBE observed at this site to pose a high risk to drinking <br /> water supplies. It is important to recognize that the City of Ripon operates several Municipal Supply <br /> Wells in close proximity to this site with moderate to high pumping rates. <br /> This letter presents a directive for an immediate full three dimensional definition and investigation of soil <br /> and groundwater contamination of fuel hydrocarbon constituents resulting from the unauthorized release <br /> documented at your site. You are hereby required to complete a Soil and Water Investigation (SWI). As a <br /> result of the current and relative absence of Benzene, Toluene, Ethyl-Benzene, and Xylenes in ground <br /> water at this site, the work plan shall focus on the distribution and migration of MTBE and any other <br /> oxygenates or supplements known or suspected by the responsible party to exist in fuel mixtures received, <br /> stored,or dispensed at this site. <br /> Analytical chemistry protocol shall include the following components in your next work plan; The <br /> results of recent groundwater monitoring indicate the presence of high levels of dissolved MTBE and <br /> Methanol. Other fuel additives may also be present in the subsurface environment at this site. You are <br /> requested to analyze all samples for TPH as Gasoline, Benzene, Toluene, Ethylbenzene, Xylenes, <br /> Methanol, Ethanol, Tertiary Butanol, MTBE, DIPS, ETBE, and TAME (see CVRWQCB attachment#1) <br /> during each sampling event until further written notice. You are requested to analyze for fuel lead <br /> scavengers including EDB and EDC during each sampling event until further written notice. You are <br /> required to analyze all soil and water samples for the above referenced compounds employing the lowest <br /> 1 <br /> A Division of San Joaquin County Health Care Services <br />