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' 3 , <br /> VOW, V_r <br /> M EM 0 R AN D U N <br /> CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD - CENTRAL VALLEY REGION <br /> 3443 R outier Road Phone: (916) 361-5600 <br /> Sacramento, CA 95827-3098 ATSS: 8-495-5600 <br /> TO: Files FROM: Robert Niblack <br /> DATE: 18 May 1987 SIGNATURE: <br /> SUBJECT: ARCO GAS STATION AT BENJAMIN HOLT AND PLYMOUTH DRIVES, <br /> STOCKTON, SAN JOAQUIN COUNTY <br /> The Arco gas station at Benjamin Holt and Plymouth Drives in <br /> Stockton was the site of a gasoline spill on 24 May 1984. Ground <br /> water contamination due to the spill has been documented. This memo <br /> relates the results of a meeting between Arco's consultant, the <br /> Regional Board, and the San Joaquin Local Health District (see <br /> attached sign-up list) . <br /> BACKGROUND <br /> On 24 May 1984, a broken leak detector was discovered in a <br /> submersible pump at the Arco service station atX908 Benjamin Holt <br /> Drive. Estimates of the magnitude of gasoline loss due to the break <br /> are 2000 gallons and 3500 gallons. A subsequent investigation by <br /> Gettler and Ryan and Emcon Associates included the installation of <br /> 12 shallow monitoring wells, ten wells on-site, and two wells 30 <br /> feet to the east of the site. Two underground storage tanks were <br /> removed, and replaced. Up to three feet of product was found <br /> floating on the ground water. A recovery well was installed, and an <br /> estimated 600 gallons of gasoline was removed from the surface of <br /> the ground water. <br /> Emcon sampled the remaining eleven monitoring wells on 10 October <br /> 1985, and analyzed the water from six of the samples for gasoline <br /> components. The other five wells had floating product depths of up <br /> to 1/411. The results of the analyses showed high levels of <br /> dissolved product in all the wells. Total gasoline ranged from <br /> 80,000 ppb to 430 ppb. Levels in the off-site wells were 430 ppb <br /> and 8,800 ppb. Benzene levels ranged from 42 to 8,000 ppb. Levels <br /> in the two off-site wells were 42 and 1, 400 ppb. <br /> Gasoline fumes were detected by Pacific Bell telephone workers in a <br /> vault about a half block from the site in April 1985. Arco hired <br /> Gettler-Ryan to evacuate the air from the vaults and lines to either <br /> side of the station. No such problem has been reported since this <br /> incident. <br /> Emcon summarized the results of the remediation, and original ground <br /> water investigation in a report dated March 1986. They feel that <br /> "little or no floating product is available for capture" by the <br />