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1 a Additional Site Assessment Report and Corrective Action Work Plan 1 • The Southland C2Mratlon,Store#20632 4627 DaVinci Drive Stockton CA Jan"ary S.1997 1.0 INTRODUCTION This report is submitted by Fluor Daniel GTI, Inc (Fluor Daniel GTI)to summarize the results of site assessment conducted at Southland Store No 20632, 4627 DaVinci Street in Stockton, California (Figures 1 and 2) Also included is a corrective action work plan for the site to be implemented during the removal of the underground storage tanks (USTs) and fuel dispenser island The scope of work for the site assessment included the collection of background information,the drilling and sampling soil from four borings, installing groundwater monitoring wells within each of the borings, collection of groundwater samples , and preparation of this report summanzing the methods and results of the work performed The work scope was designed to fulfill the requirements of the San Joaquin County Public Health Services (SJCPHS) The work scope described in this report was completed at the site between September 21 and October 17, 1997 Ali work was performed in accordance with Fluor Daniel GTI's Work Plan for Addihonal Site lnveshgabon,dated March 27, 1997,which was approved by the SJCPHS 2.0 BACKGROUND On February 21, 1997, Fluor Daniel GTI supervised the advancement of six angled and four vertical . geoprobe borings(GP-1 through GP-10) at the site Soil samples were collected from the borings at vertical depths of 5 feet to 15 feet below ground surface(BGS) The sb(angled borings(GP-1 through GP- 6)were drilled beneath the three 10,000-gallon USTs at the site as required by the SJCPHS prior to tank lining permd approval In addition,groundwater grab samples were collected from borings GP-1,GP-5, and GP-7 through GP-10 The highest benzene, methyl-tert-butyl ether{MTBE),and total petroleum hydrocarbons as gasoline (TPH- G) concentrations in the soil samples collected from the bonngs drilled February 21, 1997,was reported in sample GP-3-5'at 0 44 milligrams per kilogram (mg/kg), 12 mg/kg,and 150 mg/kg, respectively(Table 1) The highest benzene,MTBE,TPH-G concentrations in groundwater samples collected February 21, 1997, was reported in sample GP-1 at 390 micrograms per Ider(pg/..), 16,000 pgA.,and 16,000 Vg/l., respectively Presence of MTBE,reported in sample GP-8 at a concentration of 1,600 pg/L.,was confirmed at a concentration of 870 pg/L using EPA method 8260(Table 2) 3.0 SOIL AND GROUNDWATER ASSESSMENT WORK 3.1 PermittinglSitevpecffic Health and Safety Pian Fluor Daniel GTI conducted a technical review of all relevant Information provided before proceeding with site assessment work Permits for the soil borings were not required by the SJCPHS for the Installation of the four groundwater monitoring wells since permits had already been Issued for the initial site Investigation conducted on February 21, 1997 Following a complete review of site conditions, Fluor Daniel GTI revised FLUOR DANIEL GTI 20832a*rq*