SITE INFORMATION AND CORRESPONDENCE

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0 ;iECEIVED RIVER CITY PETROLEUM (CONNELL MOTOR) - NO FURTHER ACTION REQUIRED FACT SHEETi t 2 0 2012 River City Petroleum (Connell Motor) is location at 2211 North Wilson Way, Stockton, California on the west side of North Wilson Way. The main structure occupying the site is a large warehouse/truck ay AL HEALTH building. The site is currently used as a commercial tire service facility. Historically, a forklift and commercial VICES truck repair company operated throughout the large warehouse building; waste from the repair operation was apparently released through a drain line in the western portion of the site. A Phase I site investigation of the property conducted in 1999-2000, determined that waste water with solvents and oils were present in the soil and shallow ground water, west of the building. A shallow dissolved Stoddard solvent plume was identified; since 1999-2000, the plume has demonstrated a decreasing trend in dissolved concentrations of all suspected released chemicals. The eastern portion of the site was formerly a fuel card-lock fueling station. This commercial diesel and gasoline fueling operation utilized underground storage tanks (USTs) for fuel storage. In October 1986, four 10,000-gallon, steel, USTs were removed from the site; it was known at that time an unauthorized release of hydrocarbons had occurred at the site based on the site inspection log. In June 1998, three fiberglass USTs were removed. Hydrocarbon-impacted soil was encountered beneath the dispenser and the UST piping. Subsequently, a limited volume of impacted soil was excavated and removed and the excavation was backfilled. It was determined that a release of petroleum hydrocarbons [TPH-g, TPH-d, and benzene, toluene, ethylbenzene and xylene (BTEX)] had occurred from dispenser lines. The highest TPH-g and BTEX impact to soil in the upper soil zone is present at monitoring well borings throughout the former UST area. The highest TPH- g impact to soil near the water table and below the water table, to a depth of 75 feet bsg, occurred in the UST area. The aerial extent of the shallow soil contamination is limited and surrounding the former UST dispenser area and not likely present in shallow soil off-site. Since the site is fully paved, there are no direct exposure routes to the residual impacted soil. There are forty-eight ground water monitoring wells at the site which will be destroyed following site closure. Relatively significant TPH-g and BTEX compounds concentrations were previously detected in ground water samples collected directly west of the dispenser island. TPH-g and BTEX compounds were detected in ground water samples collected directly east of the former dispenser island, in the shallow ground water and towards the west under the building at the site. The vertical and the lateral extent of TPH and BTEX have been defined by monitoring well samples. Once released to the subsurface, the historical fuel contained 1,2-DCA (former leaded gasoline), which migrated to deeper depths between 100 and 200 feet. The investigations to date suggest that the source of the 1,2-DCA was the former USTs at the site. 1,2-DCA is the most widespread contaminant released at the site and underlies the western side of the building (within the former Stoddard plume area). Beginning in November 2004, a soil-vapor extraction (SVE) unit began operation at the site, to recover and mitigate the hydrocarbon releases. Remediation wells were installed in soil near the former UST and dispenser area and at the western side of the building. In-situ air sparging (IAS) wells were installed near the former UST dispenser area and east within the building. Beginning in April 2007, the IAS system began to inject air beneath the water table to remediate deeper impacted ground water. The mass of hydrocarbons removed by the SVE system demonstrated successful remediation; a total mass of approximately 41,097 pounds (lbs) of TPH-g, equivalent to a total volume of 6,500 gallons of TPHg, were documented to have been removed since remediation began. Dissolved petroleum hydrocarbon concentrations (well samples) have declined near the former UST area and are attenuating, following site remediation.