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Executive Summary 2 Southland Store No 17334,4501 North Pershing Avenue Stockton,California August 10, 1998 The highest dissolved benzene, MTBE, and TPH-G concentrations in groundwater samples collected February 20, 1997, were reported In sample GP-4 at 9,100 micrograms per liter(pg1L), 100,000 pg/L, and 150,000 pg/L, respectively Presence of MTBE was confirmed by EPA method 8260 in the same sample at 84,000 tag/L Attachment 2, Table 1 includes historical analytical results for soil samples collected at the site Between September 23 and November 26, 1997, Fluor Daniel GTI, supervised drilling and installation of one off-site and four on-site groundwater monitoring wells to depth of 35 feet to 40 feet BGS (Figure 2) The wells were installed to define the vertical and lateral extent of dissolved hydrocarbons beneath the site Selected soil samples collected during the installation of the monitoring wells were analyzed for benzene, toulene, ethylbenzene, and total xylenes (BTEX), TPH-G, total petroleum hydrocarbons- as-diesel (TPH-D) following EPA methods 8015/8020 modified, and the oxygenates tertiary Butanol (TBA), MTBE, dc-isopropyl ether(DIPE), ethyl-tertiary-butyl ether(ETBE), and tertiary-amyl-methyl ether (TAME) Maximum benzene and TPH-G concentrations were reported in sample MW-1A-25' at 0 39 mg/kg and 43 mg/kg, respectively Maximum MTBE and TBA concentrations were detected in sample MW-1A-21' by EPA method 8260 at 6 2 mg/kg and 0 51 mg/kg, respectively Since the installation of the monitoring wells, three sampling and monitoring events have been conducted at the site with the latest occuring on June 15, 1998 The highest benzene, MTBE, and TPH-G concentrations have been detected In monitoring well MW-1 at 5,000 pg/L, 21,000 erg/L, and 52,000 pg/L, respectively Depth to water at the site has ranged from approximately 14 feet to 20 feet BGS Groundwater gradient is toward the northeast Underground Storage Tank Removal/Installation During August or early September 1998, the Southland Corporation plans to remove the three 10,000- gallon single-walled steel USTs at the site and associated fuel dispensers and replace them with two 10,000-gallon double walled tanks and new fuel dispensers Prior to removal of the USTs, wells MWA and MW-1A will be properly destroyed to avoid possible damage during the tank excavation During removal of the existing USTs an estimated 150 cubic yards of tank overburden material will be removed and stockpiled on site The soil material will be sampled for proper characterization The material will either be transported from the site by a licensed waste hauler to an approved disposal facility or used as backfill material Based on the low to moderated hydrocarbon concentrations in soil samples 17334EXE LTR FLUOR DANIEL GTI `A+