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1 EDMUND G. SRowu JR. <br /> (•�'. OOVEPIIOR <br /> F. <br /> CAL I P O R N I L MD THEv,RoDRIDe EZ <br /> 7AFY <br /> FOR <br /> Water Boards <br /> oar ^ ENVIRONMENTAL PROTECt1O11 <br /> Central Valley Regional Water Quality Control Board <br /> 9 March 2017 <br /> Sharon Evans Chris Panaitescu <br /> Phillips 66 Company Thrifty Oil Company <br /> 1380 San Pablo Avenue 13116 Imperial Highway <br /> Rodeo, CA 94572 Santa Fe Springs, CA 90670 <br /> BP #172 (THRIFTY), 7647 PACIFIC AVENUE, STOCKTON, SAN JOAQUIN COUNTY, <br /> CASE# 390652 <br /> Central Valley Regional Water Quality Control Board (Central Valley Water Board) oversight of <br /> the BP#172 (Thrifty Oil) unauthorized underground storage tank (UST) release located at 7647 <br /> Pacific Street in Stockton (Site) has been transferred to Alan Buehler. Please direct all future <br /> correspondences and reports regarding the Site to Alan Buehler at the Central Valley Water <br /> Board office in Rancho Cordova. <br /> Central Valley Water Board staff has reviewed the following documents, submitted on your <br /> behalf by ATC Group Services Inc. (ATC) for the Site: <br /> • Assessment and We/l Installation Report(Assessment Report), dated 8 June 2015 <br /> • Pilot Test Summary Report(Pilot Test Report), dated 4 August 2015 <br /> Semi-Annual Groundwater Monitoring Status Report— Second Quarter 2016, (2Q16 <br /> Report) dated 11 July 2016 <br /> Currently, the Site is an active 711 convenience store, but formerly operated as BP (Thrifty Oil) <br /> service station #172, a commercial petroleum fueling facility. In June 1991, four (4) monitoring <br /> wells were installed at the Site. In July 1991, San Joaquin County Environmental Health <br /> Department (SJCEHD) filed an Unauthorized Release Report based on the results of soil and <br /> groundwater sampling from the installed wells. In July 1995, one (1) 15,000-gallon, one (1) <br /> 10,000-gallon, and two (2) 6,000-gallon unleaded gasoline USTs, one (1) 550-gallon waste oil <br /> UST, and associated dispenser islands and product piping were removed from the Site. <br /> According to Alisto Engineering Group's Tank Removal Report dated 17 November 1995, 900 <br /> cubic yards of impacted soil were removed, and disposed of off-site. <br /> In December 2007, three (3) 12,000-gallon USTs and associated dispensers and product piping <br /> were removed from the Site. The UST basin was excavated to a depth of 19 feet below ground <br /> surface (bgs), and used the resulting stockpiled soil to backfill the excavation. <br /> Since 1991, twenty-five (25) monitoring wells have been installed, and destroyed eight (8) <br /> monitoring wells. While the highest concentrations of total petroleum hydrocarbons as gasoline <br /> (TPHg) and benzene are in the deeper groundwater zone, high concentrations are present in <br /> the shallow zone as well. Groundwater flow at the Site is toward the northeast. Table 1 below <br /> presents the December 2016 (most recent) groundwater monitoring data. <br /> KARL E. LONGLEY SCD, P.E., CHAIR I PAMELA C. CREEOON P.E., BCEE, EXECUTIVE OFFICER <br /> 11020 Sun Center Drive N200,Rancho Cordova,CA 95670 1 www.waterboards.ca.gov/centralvalley <br /> Cn RECYCLED PAGER <br />