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REMEDIAL ACTION PLAN USA STATION#65 - LODI NOVEMBER, 1995 3.0 BACKGROUND �.. 3.1 Facility Description The site is located at 2500 West Lodi Avenue, in the City of Lodi, California, and consists of a •.- retail gasoline station and car wash. The site borders a shopping center/parking area to the west and south, West Lodi Avenue to the north and South Main Canal to the east. Three 12,000-gallon underground storage tanks (USTs) and three fuel dispensing islands are �- present at the site. The tanks and dispensers store and dispense regular,plus and premium grade unleaded gasolines. At least one of the tanks has been used to store leaded gasoline in the past. The surface elevation of the site (Applied Geosystems,December 5, 1989) is approximately 37 to 38-feet above mean sea level (MSL). A "Site Plan" showing the locations of the USTs and fuel dispensing islands is presented as Figure 2. 3.2 Project History Results of a limited site investigation completed in March, 1987 ("Preliminary Environmental Investigation" dated March 16, 1987 performed by Pacific Environmental) detected hydrocarbons in the soil and groundwater beneath the site. The investigation included drilling and sampling of four soil borings. Two of the borings (S-A and S-B) were advanced to depths of 20-feet and backfilled. The remaining two borings were advanced to depths of approximately 50.5-feet and completed as groundwater monitoring wells (S-1 and S-2). Following well installation, the groundwater level was recorded at approximately 41 and 40-feet below the ground surface (bgs) in S-1 and S-2,respectively. This work was commissioned by Shell Oil Company who was considering purchasing the site at the time. In August, 1987,Applied Geosystems ("Delineation of Hydrocarbon Contamination and Hydrogeologic Characterization",report no.87050-2, dated October 13, 1987) completed �- installation of three new groundwater monitoring wells (MW-1,MW-2 and MW-3). The wells were completed to depths of approximately 60-feet bgs. Soil samples collected from the borings during drilling were non-detect for total petroleum hydrocarbons (TPH), total volatile hydrocarbons (TVH) and benzene, toluene, ethylbenzene, and xylenes (BTEX). Groundwater samples collected and analyzed from each boring detected TVH. `r In August, 1988, USA requested that Applied Geosystems resample the wells. Analytical results again detected TVH in each of the wells ("Letter of Quarterly Groundwater Monitoring, report no. 87050-2, dated November 10, 1988). To further define the lateral extent of the impacted groundwater, USA requested that Applied Geosystems complete four additional monitoring wells in the down gradient direction (MW-4, MW-5, MW-6 and MW-7). The wells were completed to total depths of approximately 60-feet bgs. L 2