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1 Chronology <br /> 9110 Thornton Road <br /> Stockton CA 95209 <br /> Site Code: 1886 <br /> The site is currently an operating 7-11 convenience store and is located on the <br /> north-east corner of Thornton Road and Waudman Ave, San Joaquin County APN <br /> 072-450-20 (formerly 076-330-15). The site had previously operated underground <br /> storage tanks. In 1986, an unauthorized release was documented and Southland, <br /> responded by ceasing operation of the tank system and initiating an investigation <br /> of soil and groundwater. Nearby domestic welts were impacted and Southland <br /> responded by providing bottled water. Over a nine year period, Southland <br /> remediated soil and groundwater contamination, continued monitoring of nearby <br /> domestic wells and provided bottled water to nearby residences. San Joaquin <br /> County Public Health Services, Environmental Health Division and the Central <br /> Valley Regional Water Quality Control Board has evaluated the site for closure and <br /> has determined that site closure/certification is warranted. <br /> E <br /> Tank Operations <br /> Three underground storage tanks were installed in 1979. <br /> Southland filed an unauthorized release report on April 11, 1986 following a failed <br /> tank/line test. The report indicated that the approximate date the discharge began <br /> was November 1985. On May 5, 1986, the product lines between the pump island <br /> and tank pit were exposed for visual inspection. <br /> A review of inventory records indicated a 3,000 to 5,000 gallon loss of unleaded <br /> product. Southland discontinued selling and storing gasoline in one of the three <br /> underground storage tanks on May 7, 1986 due to a failed precision test of a <br /> product pipeline. The remaining storage tanks were abandoned and emptied when <br /> this location discontinued selling gasoline on November 11 , 1986, due to the <br /> liability and perceived poor condition of the :remaining product pipeline. <br /> During an initial investigation in 1986, it was observed that the underground <br /> storage tanks were in good condition°and had been tar coated and installed in a <br /> good bead of clean sand. The failed vinyl coated pipelines were backfilled with a <br /> clay material that was native to the site and the exposed pipe ends and <br /> connections were not wrapped. Severe 'point corrosion was observed to have <br /> occurred at these unprotected locations, while the remainder of the protected pipe <br /> appeared to be in good condition. <br /> Unauthorized Release Investigation <br /> On May 6, 1986, the soil and groundwater investigation was initiated with the <br /> installation of four monitoring wells. Freeproduct was noted at the time of <br /> installation. ' A total of 27 groundwater wells and 4 vapor extraction wells were <br /> installed between 1986 and 1989. <br />