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L:­,­o G.BRowR JR. <br /> ooveRHou <br /> P R " MA"REW RODRIQUEZ <br /> Water Boards <br /> MOHMENt At PROiFi:tiOR <br /> Central Valley Regional Water Quality Control Board <br /> 23 February 2017 <br /> Randy Coil <br /> Atlantic Richfield Company <br /> 501 Westlake Park Boulevard, WL1-28.16B <br /> Houston. TX 77079 <br /> FORMER ARCO STATION #6100, 25775 SOUTH PATTERSON PASS ROAD, TRACY, <br /> SAN JOAQUIN COUNTY, CASE# 390265 <br /> California Regional Water Quality Control Board, Central Valley Region (Central Valley <br /> Water Board) staff reviewed the Conceptual Site Model (CSM) dated 30 December 2016. <br /> submitted on your behalf by Arcadis U.S. Inc. (Arcadis) for the Former ARCO #6100 property <br /> at 25775 South Patterson Pass Road in Tracy (Site). The CSM includes a summary of Site <br /> assessment and remediation to date, an evaluation of the Site compared to Low Threat <br /> Closure Policy (LTCP) criteria, and proposals for soil assessment and remedial system <br /> rebound vapor testing. <br /> The Site is currently a 76-branded active commercial petroleum fueling facility, located in the <br /> northwest corner of the intersection at South Patterson Pass Road and Interstate 580 in <br /> Tracy. One (1) 550-gallon waste oil tank was removed from the Site in 1987. The volume <br /> and fate of soil removed was not reported. The waste oil tank basin was excavated to <br /> between 6 and 13 feet bgs. Between November 1990 and February 1991, four (4) 6,000- <br /> gallon and one (1) 10,000-gallon gasoline USTs and associated product piping were <br /> removed from the Site. Approximately 2,500 cubic yards of hydrocarbon impacted soil was <br /> removed from the fuel UST basin and disposed of off-site. In 2002, approximately 315 tons <br /> of impacted soil were removed from the Site during product piping and dispenser island <br /> upgrades. Between September 2000 and March 2010, approximately 284 gallons of light <br /> non-aqueous phase liquid (LNAPL) and groundwater were removed from eight (8) Site wells. <br /> In October 2007, approximately 8 pounds of hydrocarbons were removed during an off-site <br /> SVE pilot test. <br /> SVE and air sparge (AS) are currently being implemented at the Site, though the system has <br /> been down for repairs since July 2016. Since May 2014, approximately 6,678 pounds of <br /> vapor phase hydrocarbons have been removed. SVE was previously implemented at the <br /> Site between March 2004 and August 2010, removing approximately 180,718 pounds of <br /> vapor phase hydrocarbons. <br /> KARL E. LONGLEY SCD, P.E.,CI4AIR I PAMELA C. CREEDON P.E., SCEE, EXECU'FiYE OFFICER <br /> 11020 Sun Center Drive#200.Rancho Cordova.CA 95670 1 www.waterboarde.ca.0ov/centralvalley <br /> �;p REOrCLED PAPEa <br />