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UST and Product Line Replacement-Tosco 76 Branded Facility No. 11193,Stockton,CA <br /> April 12,1999 <br /> Well MW-1 was properly destroyed as required by Water Well Standards (Bulletins 74-81 and 74-90) <br /> and SJCPHS guidelines. The 2-inch diameter well was destroyed by filling the well casing from <br /> bottom(32 feet deep)to surface with neat cement by the use of a tremie pipe and applying compressed <br /> air to force grout out of casing into filter pack. <br /> Groundwater Sampling from the Gasoline UST Excavation <br /> On December 17, 1998,one groundwater sample was collected from the gasoline UST pit prior to new <br /> UST installation. Ms. Carol Oz of the SJCPHS was present to witness groundwater sample collection. <br /> The UST pit was excavated to a depth of approximately 16 feet bgs by Paradiso. Groundwater was <br /> observed in the pit at a depth of approximately 15 feet bgs. One water sample (Water-FTE) was <br /> collected from the UST pit by the use of a disposable bailer. <br /> The sample was analyzed for TPHg,BTEX,MtBE, and Oxygenated Compounds. TPHg was detected <br /> at 17,000 ppb, benzene at 1,500 ppb, MtBE (EPA 8020) at 100,000 ppb, and MtBE (EPA 8260) at <br /> 120,000 ppb. Oxygenated Compounds, other than MtBE, were not detected, except for t-Amyl Methyl <br /> Ether detected at a concentration of 210 ppb. <br /> Product Piping/Dispenser Removal and Soil Sampling <br /> On December 22, 1998, the existing 2-inch-diameter single-wall fiberglass product piping and <br /> dispensers were removed. Nine soil samples were collected from the base of the product piping <br /> trenches. Ms. Carol Oz of the SJCPHS was present to witness the soil sampling. Four samples (Dl <br /> through D4) were collected from beneath the product dispenser/piping connections at depths ranging <br /> between 4.0 and 5.0 feet bgs. Five samples (P1 through P5) were collected from the product piping <br /> trenches at depths ranging between 4.5 and 7.0 feet bgs. Native soil in the vicinity of the product <br /> piping trenches consisted of clayey silt. <br /> The nine soil samples were analyzed for TPHg, BTEX, MtBE, and Oxygenated Compounds. TPHg <br /> was detected in samples D1, D2, D3, D4, PI, P3, and P4 at concentrations ranging between 9.3 and <br /> 1,600 ppm. The nine samples contained MtBE(EPA Method 8260) at concentrations ranging between <br /> 0.180 ppm and 1.8 ppm. Oxygenated Compounds, other than MtBE, were not detected in samples D1 <br /> through D4, and P1 through P5. <br /> Product Piping Trench Over-Excavation and Soil Sampling <br /> After review of the analytical results of the initial product piping trench soil samples, GR personnel <br /> returned to the site on December 29, 1998, to collect confirming soil samples following additional <br /> excavation in the vicinity of the product piping trenches. Ms. Margaret Lagorio of the SJCPHS was <br /> present to witness the excavation and soil sampling activities. Additional excavation was conducted in <br /> the vicinity of each of the soil samples D1, D2, D3, D4, and P1 to a depth of approximately 10.5 feet <br /> 140205.02 <br /> 3 <br />