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G¢oHydrologic Consultants, Inc. 1 .0 INTRODUCTION On behalf of Thrifty Oil Co. (Thrifty),GeoHydrologic Consultants, Inc. (GHC), oversaw the underground storage tank(UST) removal activities which included well abandonment,replacement well installation, reconfiguration of conveyance piping, removal of three USTs and associated dispensers and fuel piping,and soil sampling activities at 7647 Pacific Avenue, Stockton, California(the"Site")as shown in Figures 1 and 2.The oversight agency for the UST removal at this Site is the San Joaquin County Environmental Health Department(SJCEHD). Work was conducted in accordance with the Revised Workplan for Well Abandonment, Replacement Well Installation, Reconfiguration of Conveyance Piping, and Interim Remedial Action by Over Excavation in Conjunction with the UST System Removal,prepared by GHC and dated November 6, 2007,and the Addendum to Revised Workplan for Well Abandonment, Replacement Well Installation, Reconfiguration of Conveyance Piping, and Interim Remedial Action by Over Excavation in Conjunction with the UST System Removal,also prepared by GHC and dated December 17,2007.This work was approved by SJCEHD in their letters to Thrifty dated December 11, 2007 and January 29,2008. 1.1 Site Description The Site is a former operating retail gasoline sales facility and convenience store located on the southwest comer of the intersection between Pacific Avenue and Rivera Road in Stockton, California(Figure 1). Site improvements included three underground storage tanks (USTs),three pump islands with one dispenser each,and a convenience store(Figure 2). In December 2007,the three USTs,dispensers,and associated piping were excavated and removed from the Site, and the Site is currently in non-operational status. The site has been occupied as a service station since 1964 when American Oil built and began operating a service station.Thrifty acquired the site in 1972 and in 1991 leased the site to BP Oil. ConocoPhillips began station operations in 1994, and operated at the Site through year 2006.A remediation compound is currently located in the northwest corner of the Site. 2.0 SITE CHARACTERIZATION DATA 2.1 Geology/Hydrogeology 2.1.1 Regional Geology The site is located in the San Joaquin Valley of the Central Valley geomorphic province. Geologically,the Central Valley is a large elongate north-west trending asymmetric structural trough that has been filled with a tremendously thick sequence of sediments ranging in age from Jurassic to Recent.The basin has a regional southward tilt,which is interrupted by two significant cross-valley faults. The northernmost fault,the Stockton TOC 172 UST Removal Report Final Page I