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f UST and Product Line Replacement-Tosco 76 Branded Facility No 11193,Stockton,CA lApnII2,1999 t Well MW-1 was properly destroyed as required by Water Well Standards (Bulletins 74-81 and 74-90) and SJCPHS guidelines The 2-inch diameter well was destroyed by filling the well casing from bottom(32 feet deep) to surface with neat cement by the use of a tremie pipe and applying compressed air to force grout out of casing into filter pack Groundwater Sampling from the Gasoline UST Excavation On December 17, 1998, one groundwater sample was collected from the gasoline UST pit prior to new UST installation Ms Carol Oz of the SJCPHS was present to witness groundwater sample collection The UST pit was excavated to a depth of approximately 16 feet bgs by Paradiso Groundwater was observed in the pit at a depth of approximately 15 feet bgs One water sample (Water-FTE) was collected from the UST pit by the use of a disposable bailer The sample was analyzed for TPHg, BTEX, MtBE, and Oxygenated Compounds TPHg was detected at 17,000 ppb, benzene at 1,500 ppb, MtBE (EPA 8020) at 100,000 ppb, and MtBE (EPA 8260) at 120,000 ppb Oxygenated Compounds, other than MtBE, were not detected, except for t-Amyl Methyl Ether detected at a concentration of 210 ppb Product Piping/Dispenser Removal and Soil Sampling On December 22, 1998, the existing 2-inch-diameter single-wall fiberglass product piping and dispensers were removed Nine soil samples were collected from the base of the product piping trenches Ms Carol Oz of the SJCPHS was present to witness the soil sampling Four samples (D1 through D4) were collected from beneath the product dispenser/piping connections at depths ranging between 4 0 and 5 0 feet bgs Five samples (P1 through P5) were collected from the product piping trenches at depths ranging between 4 5 and 7 0 feet bgs Native soil in the vicinity of the product piping trenches consisted of clayey silt The nine soil samples were analyzed for TPHg, BTEX, MtBE, and Oxygenated Compounds TPHg was detected in samples D1, D2, D3, D4, P1, P3, and P4 at concentrations ranging between 9 3 and 1,600 ppm The nine samples contained MtBE (EPA Method 8260) at concentrations ranging between 0 180 ppm and 1 8 ppm Oxygenated Compounds, other than MtBE, were not detected in samples D1 through D4, and PI through P5 Product Piping Trench Over-Excavation and Soil Sampling After review of the analytical results of the initial product piping trench soil samples, GR personnel returned to the site on December 29, 1998, to collect confirming soil samples following additional excavation in the vicinity of the product piping trenches Ms Margaret Lagono of the SJCPHS was present to witness the excavation and soil sampling activities Additional excavation was conducted in the vicinity of each of the soil samples D1, D2, D3, D4, and P1 to a depth of approximately 10 5 feet 14020502 3