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concentration of GRO (900 mg/Kg) and benzene (3 4 mg/Kg) were reported for the soil sample collected from boring B-42 at 98 feet bgs Both of these samples were collected immediately below the contact with sand zone 2 Petroleum hydrocarbons were reported for soil samples collected between 17 and 114 feet bgs (boring B-39), 51 and 113 feet bgs (boring B-40), 49 and 97 feet bgs (boring B-41), and 54 to 98 feet bgs (boring B-42) The lateral extent of subsurface petroleum hydrocarbon impact to soil is not fully characterized south and southeast of the site Increased residual petroleum hydrocarbon concentrations were generally observed for soil samples collected near sand zone 1 and sand zone 2 in borings B-39 through B-42, suggesting that these stratum may be providing a preferential pathway for subsurface movement of the petroleum hydrocarbon impact Soil analytical data collected from borings B-33 through B-42 appears to show that the vertical extent of subsurface petroleum hydrocarbon impact does not extend more than approximately 10 feet deeper than the base of sand zone 2 Based on this observation, the fine grained soils situated immediately beneath sand zone 2 appear to be of sufficiently low permeability to impede additional vertical migration of the petroleum hydrocarbons at these depths MTBE was only reported for the soil samples collected from boring B-39 between approximately 17 and 45 feet bgs, at concentrations ranging from 0 008 mg/Kg to 0 35 mg/Kg 1,2-DCA was reported for the samples collected from boring B-39 at approximately 45 feet bgs (0 027 mg/Kg) and 64 feet bgs (0 014 mg/Kg) 3.4 Extent of Petroleum Hydrocarbon Impact to Groundwater Shallow Screened Wells Free product has historically been measured in wells VW-1 (sheen to 0 07 feet in thickness) and VW-4 (sheen to 0 21 feet in thickness) Free product has not been observed in wells VW-1 or VW-4 since July 2003 The lateral extent of free product in the subsurface appears to be adequately characterized in the shallow screened wells GRO and benzene were reported for samples collected from on-site wells VW-1 through VW-4 at the time of the second quarter 2004 groundwater sampling event GRO concentrations for these samples ranged between 36,000 micrograms per liter (µg/L) and 110,000 µg/L, benzene concentrations for these samples ranged between 9,000 µg/L and 32,000 µg/I. 1,2-DCA was reported for the samples collected from wells VW-1 (2,000 µg/L) and VW-4 (960 µg/L) MTBE (970 µg/L) was reported for the sample collected from well VW-3 Dissolved petroleum hydrocarbons were not detected in the sample collected from off-site well MW-2 GRO (81 µg/L) and benzene (4 3 gg/L) were reported for the sample collected from off- site well MW-13 Deeper Screened Wells Free product has historically been measured in well MW-1 A maximum free product thickness 0 of 189 feet was measured in December 2000 Following initiation of free product removal by P 1BP-Arco for URS%61001Repottslarw610U-u wssrr)ent utrLupdate doc Page 9 5 M 7115