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r '� - <br /> ealifornia"" gional Water Quality` Control Board <br /> Central Valley Region <br /> Winston H.Hickox Steven T.Butler,Chair <br /> Secreta Gray Davis <br /> fice <br /> '�for Sacramento Main Of <br /> Environmental Intemet Address: http://www.swrc6.ca.gov/—rwgch5 Governor <br /> Protectian 3443 Routier Road,Suite A,Sacramento,California 95 82 7-3 003 <br /> Phone(916)255-3000•FAX(916)255-3015 <br /> TO: Gordon L. Boggs FROM: Mark R. List <br /> UST Program Manager Engineering Geologist <br /> DATE: 2 June 1999 SIGNATURE: <br /> SUBJECT: FILE REVIEW FOR CLOSURE CONCURRENCE DETERMINATION, <br /> CALIFORNIA WELDING SUPPLY, 1000 EAST 11 TH STREET, TRACY, <br /> SAN JOAQUIN COUNTY <br /> At the request of the San Joaquin County Environmental Health Division (SJCEHD), a file review was <br /> completed to determine if Regional Board staff concur with the SJCEHD determination of no further <br /> action required at this site. This information was obtained during my review of the Regional Board <br /> casefle, and during discussions with Ms. Carol Oz of San Joaquin County. <br /> Background: <br /> On 12 June 1996, two 550-gallon underground storage tanks (USTs) were removed from the site. <br /> Strong petroleum odors were noted during the tank removal.' Total Petroleum Hydrocarbons as diesel <br /> and gas, BTEX, and MTBE were identified in soil samples collected at the site. About 150 cubic yards <br /> of contaminated soil was excavated from the former tank pit on 19 September 1995. Between July and <br /> October 1996, site assessment activities were completed by installing eight soil borings and three <br /> monitoring wells. Groundwater contamination was never identified in any of the monitoring well <br /> samples. The on-site domestic well was sampled and analyzed by EPA Method 524.2 and was <br /> non-detect for all constituents analyzed. <br /> During 21 August 1998 field activities, 50-cubic yards of contaminated soil was removed from the <br /> former dispenser area by overexcavation. Estimates of remaining TPHg, TPHd, and benzene <br /> contamination were presented in a site closure report, with an estimated 5.2 lb. (0.86 gals) of TPHg, <br /> 8.8 lb. (1.20 gals) of TPHd, and 0.06 lb. (0.008 gals) of benzene is calculated to remain in subsurface <br /> soils. Only trace concentrations of MTBE were identified. <br /> Summary: <br /> Soil contamination (TPHd, TPHg, BTEX, and MTBE) was identified during tank removal and soil <br /> boring activities. Three monitoring wells were installed and sampled, and the on-site domestic well was <br /> also sampled, with no groundwater contamination reported in any well. About 200 cubic yards of <br /> contaminated soil was overexcavated from the former UST pit and dispenser area. Remaining <br /> contamination does not appear to pose a threat to water quality. Concurrence with the SJCEHD no <br /> further action required decision is appropriate. <br /> California Environmental Protection Agency <br /> �a Recycled Paper <br />