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as 120 ag/l, respectively. MTBE has been detected in samples from wells MW 1 and MW3 r� at concentrations as high as 6.7 pg/l. ETBE and TAME have not been detected in any of the wells sampled. TPH-d concentrations exceeded TPH79 concentrations in the samples containing both analytes. Impacted soil was present below the ground water table at the time remediation began, due to ' historically lower ground water elevations at the site during which time a portion of the unauthorized hydrocarbon release occurred. The former UST area was impacted by diesel fuel compounds, but also is impacted by significant concentrations of gasoline fuel compounds. The volume of soil addressed by the remediation system was estimated to be 645 cubic meters based on the limited lateral extent of the vadose zone contamination and a depth to ground water of 20 feet bsg. The generalized mass of vadose-adsorbed TPH-g was approximately 65.2 lbs or 29.58 kg and generalized mass of adsorbed TPH-d was approximately 77.l 6 lbs or 35 kg. The total volume of impacted soil addressed by the remediation system was estimated to be 1,240 cubic meters,from the base of the former UST excavation to the depth of 30 feet bsg. The total mass ' of adsorbed TPH-g was approximately 123.5 lbs or 56.8 kg and mass of total adsorbed TPH-d was approximately 150 lbs or 68.2.kg. Hydrocarbon-impacted ground water in the former UST area has higher average TPH-g:TPH-d rations(0.702- 1.852) indicating a greater contribution to groundwater of TPH-g in the former UST area. ' SOIL AND GROUND WATER REMEDIATION On 25,26 and 27 April 2000, four air-sparge pilot borings and eleven soil vapor extraction soil pilot borings were advanced at the site; with borings IAS 1 through IAS4 completed as were completed ' as two-inch diameter air sparging wells, drilled to a total depth of 25 feet bsg with a 5-foot screen interval. While two vertical zones of remediation wells were installed as follows: borings VW3A, ' VW8 and VW9A were completed as were completed as vapor extraction wells, drilled to a total depth of approximately 13 feet bsg and completed with a 5-foot screen intervals and borings VW3B,VW4, VW5, VW6, VW7, VW9B , VW 10 and VW 11 were completed as vapor extraction ' wells, drilled to a total depth of approximately 18 feet bsg and completed with a 5-foot screen intervals. Soil samples were collected from air-sparge pilot borings IAS 1 to 1AS4 ahead.of the drill bit using a core barrel. TPH-g was detected in each of the sample at concentrations as high as 990 mg/kg. TPH-d was also detected in each sample analyzed at concentrations as high as 1,000 mg/kg. BTEX ' compounds were detected in each sample analyzed.Benzene was detected at concentrations as high as 0.63 mg/kg at a depth of 18 feet bsg. The only fuel additive detected was 1,2 DCA at a concentration up to 20 micrograms per kilogram (gg/kg). Advanced CeoEnvironment21,Inc.