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PUBLIC HEALTH SERVICES QPA!!N <br /> �o <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 95202 r1( 11 moa P <br /> 209/468-3420 ti, J <br /> MAY 12 WS <br /> LORI CASIAS <br /> STATE WATER RESOURCES CONTROL BOARD <br /> DIVISION OF CLEAN WATER PROGRAMS <br /> LOCAL OVERSIGHT PROGRAM <br /> P 0 BOX 944212 <br /> SACRAMENTO CA 94244-2120 <br /> RE: PETITION FOR REVIEW OF LOCAL AGENCY PROGRAM ACTION, FORMER <br /> UNOCAL SERVICE STATION 187, 437 EAST MINER AVENUE, STOCKTON, <br /> CALIFORNIA, SAN JOAQUIN COUNTY, SITE NO. 1181, FILE NO. P98-188 <br /> San Joaquin County Public Health Services, Environmental Health Division (PHS/EHD) <br /> provides the following response to the above referenced petition. <br /> The site is currently a vacant lot in downtown Stockton with retail businesses, a motel, <br /> and an apartment building in the surrounding area. According to UNOCAL they <br /> operated a service station at the site from 1922 until 1992. UNOCAL has stated that <br /> two 1,000 gallon gasoline and one 550 gallon waste oil underground storage tanks <br /> (UST's) were removed from the southeast comer of the site in 1967. These UST's were <br /> replaced with two 10,000 gallon gasoline and one 280 gallon waste oil UST's which <br /> were installed on the site northwest of the location of the UST's removed in 1967. <br /> The site investigation information gathered to date indicates that the petroleum <br /> hydrocarbon soil and groundwater contamination, both on and off site, resulted from the <br /> operation of the UST's removed in 1967. Soil samples collected in October 1993, in the <br /> southeast corner of the site revealed soil contamination to 31.5 feet below surface grade <br /> (bsg). Soil samples collected in July 1994 in the same area of the site, revealed soil <br /> contamination to 45.5 feet bsg. Analysis of soil samples collected below 45.5 feet bsg <br /> has not been performed. Therefore, the vertical extent of soil contamination remains <br /> undefined in this area. Because the vertical extent of the soil contamination has not yet <br /> been defined, the minimum depth for adequate lateral plume investigation has not been <br /> determined and lateral definition is not complete. <br /> In a letter dated January 3, 1994, PHS/EHD informed UNOCAL that the vertical and <br /> horizontal extent of soil contamination had not been defined and requested a <br /> groundwater investigation. In letters dated November 4, 1994, December 23, 1994, <br /> June 3, 1997 and June 25, 1997, PHS/EHD again informed UNOCAL that the vertical <br /> extent of the contamination was not defined. During 1995, 1996 and 1997 PHS/EHD <br /> strongly encouraged UNOCAL to perform vapor extraction feasibility tests, since the <br /> highest soil concentrations identified to date were above the water table level. However, <br /> this opportunity was ignored. <br /> A Division of San Joaquin County Heaich Carc Services <br />