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W <br /> HEALTH SERVICES FILE COP Y <br /> PUBLIC OP� u ! N C <br /> SAN JOAQUIN COUNTY % <br /> ENVIRONMENTAL HEALTH DIVISION " .. ` <br /> Karen Furst, M.D., M.P.H., Health Officer <br /> 304 East Weber Avenue, Third Floor • Stockton, CA 95202 ` ' F6 " <br /> 209/468-3420 <br /> OCT 2 6 2000 <br /> R. J. COCHRAN <br /> CHEVRON PRODUCTS COMPANY <br /> P O BOX 6004 <br /> SAN RAMON CA 94583-0804 <br /> RE: Former Chevron Station No. 9-8632 SITE CODE: 1408 <br /> 575 West Grant Line Road <br /> Tracy Ca 95376 <br /> San Joaquin County Public Health Services, Environmental Health Division (PHD/EHD) is the lead agency <br /> providing the oversight of the investigation and cleanup of releases from underground storage tanks (UST) <br /> within San Joaquin County. PHS/EHD has a contract with California State Water Resources Control Board - <br /> (SWRCB) to conduct an UST corrective action program. <br /> On May 20, 1994,. four USTs were removed at the above referenced site (site) including three 10,000- <br /> gallon gasoline USTs and one 1000- gallon waste oil UST. Additionally, one oil/water separator (sump) <br /> and two semi-hydraulic hoists were also removed at the site. Soil and groundwater samples collected at the <br /> site evidenced petroleum hydrocarbon contamination and a ground water investigation was required. Four <br /> monitoring wells were installed at the site following an overexcavation of contaminated soil. On <br /> September 7, 1995, the first quarter of groundwater sample results evidenced petroleum hydrocarbon <br /> contamination in all four monitoring wells. <br /> Recently, PHS/EHD has been receiving reports that suggest that petroleum hydrocarbons originating at <br /> your site have been migrating towards other sites. On May 30, 1996, a report submitted to PHS/EHD by <br /> Th�Sarr3oaqum-Cbrnpany,Inc. representing-Rud-y-Sanchezat248O-TmeyRoulevard-(direcctly_north of <br /> your site) contains soil and groundwater sample results that evidence petroleum hydrocarbon (gasoline) <br /> contamination including methyl tertiary butyl ether (MTBE) . Moreover, two additional samples taken east <br /> of your former USTs also evidence similar contamination. The source of this contamination appeared to be <br /> from the unauthorized release at your site. <br /> A second report, submitted to PHS/EHD on September 20, 2000 by Advanced GeoEnvironmental, Inc., <br /> representing the property owner at 541 West Grant Line Road (located northeast of your site) contains soil <br /> and groundwater sample results that evidence petroleum hydrocarbon and MTBE contamination. The <br /> source of the contamination on this property also appears to be coming from the unauthorized release at <br /> your site. <br /> Although the current groundwater flow direction at your site appears to be to the northwest, groundwater <br /> flow may have been more easterly in an earlier period during your unauthorized release. A report prepared <br /> by Kaprealian Engineering, Inc. on September 12, 1986, representing Mobil Oil Corporation at the UST <br /> site located at 2375 Tracy Boulevard, includes a potentiometric surface reap which suggests that the <br /> groundwater flow direction at that time was north/northeast. <br /> In the most recent report received from Chevron by PHS/EHD for sampling performed during the Fourth <br /> Quarter of 1999, groundwater results for all on-site monitoring wells evidenced contamination. <br /> Contaminant concentration were as high as 3580 micrograms per liter (µg/1) for total petroleum <br /> hydrocarbons as gasoline ; 462 Jig/l for benzene; 27µg/l for toluene; 148 µg/1 for ethylbenzene; 341 µg/1 for <br /> xylene; 334 µg/1 for total petroleum hydrocarbon as diesel; and 533 µg/1 for MTBE. <br /> A Division of San Joaquin County Health Care Services <br />