COMPLIANCE INFO_1998 REMOVAL AND INSTALL

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UST and Product Line Replacement-Tosco 76 Branded Facility No.11193,Stockton,CA April 12,1999 Services Environmental Health Division (SJCPHS) and the City of Stockton Fire Department were present at the site during UST removal. Representatives of the SJCPHS were present during well destruction,groundwater sampling, soil sampling, and over-excavation of the product piping trenches. Gasoline UST Removal and Soil Sampling On December 10, 1998, two 10,000-gallon and one 8,000-gallon single-wall fiberglass gasoline USTs were removed from the site. Upon removal, the USTs were visually inspected for evidence of failure. No holes or cracks were observed in the tanks. Ms. Carol Oz and Ms. Letitia Briggs of the SJCPHS and Mr. Kent Miller of the City of Stockton Fire Department were present to witness UST removal and sampling activities. The USTs were removed from the site and disposed of by Ecology Control Industries (ECI)of Richmond, California. Limits of the gasoline UST pit are shown on Figure 2. Native soil in the vicinity of the gasoline UST pit consisted primarily of sand. Per the direction of Ms. Briggs of the SJCPHS, six soil samples, labeled IE, 1W, 2E, 2W, 3E, and 3W, were collected from the base of the gasoline UST pit at depths of approximately 15.0 feet below ground surface (bgs). Sample point locations are shown on the attached Figure 2. Following soil sampling, groundwater was observed entering the excavation from the sidewalls at depths ranging between 14.5 and 15 feet bgs. All soil samples from the gasoline UST pit were analyzed for Total Petroleum Hydrocarbons as gasoline(TPHg), by Environmental Protection Agency (EPA) Method 5030/8015 Modified, Benzene, Toluene, Ethylbenzene, Xylenes (BTEX), and Methyl tert-Butyl Ether (MtBE) by EPA Method 8020, and Oxygenated Compounds by EPA Method 8260. TPHg, was not detected in five of six soil samples (1E, 1W, 2E, 2W, and 3E). Sample 3W contained TPHg (reported by the laboratory as gasoline and unidentified hydrocarbons C6-C12) at 31 parts per million (ppm). Benzene was not detected in sample 2E, and was detected in all other five samples at concentrations ranging between 0.025 ppm and 0.27 ppm. Oxygenated compounds, other than MtBE, were not detected in any of the six soil samples from beneath the gasoline USTs. MtBE was detected in all six samples at concentrations ranging between 5.8 ppm and 86 ppm (EPA Method 8020), and 11 ppm and 80 ppm (EPA Method 8260). Groundwater Monitoring Well Destruction On December 11, 1998, GR observed Woodward Drilling Co. destroy one groundwater monitoring well (MW-1). The well was destroyed to allow enlargement of the existing UST pit for installation of new USTs. Ms. Carol Oz of the SJCPHS was present to witness the well destruction. The location of former well MW-1 is shown on the attached Figure 2. Copies of the California Department of Water Resources (DWR) Well Completion Report and well destruction permit #017826 issued by the SJCPHS are attached. 140205.02 2 .