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STATE OF CALIFORNIA - Environmental Protellix Agency PETE WILSON, Governor <br /> CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD <br /> CENTRAL VALLEY REGION <br /> 3443 Routier Road, Suite A <br /> Sacramento, CA 95827-3098q� <br /> PHONE: ;9161 255-3000 <br /> FAX: i91 fit 255-3015 <br /> 17 August 1993 <br /> Lambert Barnum <br /> P.O. Box 1071 <br /> San Andreas CA 95650 <br /> STAN MORRI FORD, 104 WEST ELEVENTH STREET, TRACY, SAN JOAQUIN COUNTY <br /> In a letter dated 6 August 1992, San Joaquin County Public Health Services requested Regional <br /> Board concurrence with their closure of the above site. I have reviewed the file and have the <br /> following comments. <br /> On the last reported ground water sampling, dated July 1991, the chemicals 1,1,1 trichloroethane, <br /> 1,1 dichloroethane, tetrachloroethylene, 1,1 dichloroethylene, and tetrachloroethane were detected in <br /> the site's three ground water monitoring wells. Monitoring well 1, which has detected halocarbons <br /> in all four monitoring episodes, is immediately downgradient of the previous waste oil tank. It is <br /> very possible that cleaning solvents containing such chemicals as 1,1,1 trichloroethane were placed. <br /> in the waste oil tank when working on cars. No solvents were found in the soil samples during tank <br /> removal; however, heavy solvents such as 1,1,1 trichloroethane may degrade in soil while not <br /> degrading in water. <br /> In the 27 August 1991 Final Report, your consultant, Murray and Associates, argued that the <br /> halocarbons may have come from the car wash operation on the southern end of the property. This <br /> argument is supported by pointing out that halocarbons were detected in monitoring well 2, which is <br /> upgradient of the former waste oil tank location, but downgradient from the car wash area. <br /> However, the ground water gradient was based on only one episode of water surface elevations, 31 <br /> January 1990. Also, it seems unlikely with the entire area cover by asphalt that the solvents could <br /> travel to the ground water directly below the site. <br /> We request that ground water from the three monitoring wells continue to be analyzed for the same <br /> chemicals as the July 1991 sampling event. Water surface elevations should be measured and <br /> gradients calculated each time ground water samples are taken. After four consecutive quarters of <br /> ground water analysis have taken place with no detectable ground water contamination, you may <br /> wish to request closure from the Regional Board. We will keep this site open in our underground <br /> tanks unit until the continued ground water contamination is resolved. <br /> If you have any questions, please call me at 255-3119. <br /> W�r� - <br /> F BRAUNSTEIN <br /> Project Engineer, Underground Tanks Unit <br />