ARCHIVED REPORTS_XR0011964 - Laserfiche WebLink

Home Browse Search

. • The source of the groundwater observed in the shallow and deeply screened wells beneath the site can not be positively deterrruned at this time Percolation of meteonc water into the subsurface, leakage from on-site water pipes, and recharge from the on-site water supply well appear to be possible sources of the groundwater • The lateral extent of free product thickness appears to be adequately assessed on-site and off-site • The bulk of the petroleum hydrocarbon mass appears to be situated above approximately 45 feet bgs on-site, with localized high concentrations encountered on-site between approximately 45 and 80 feet bgs The vertical and lateral extent of subsurface petroleum hydrocarbon impact appears to be adequately characterized on-site • Increased residual petroleum hydrocarbon concentrations were generally observed for soil samples collected near sand zone 1 and sand zone 2 zn 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 ® Petroleum hydrocarbons were reported in soil samples collected from borings B-39 through B-42 The highest concentrations of GRO (900 mg/Kg) and benzene (3 4 mg[Kg) were reported for a soil sample collected from boring B-42 at 98 feet bgs The lateral extent of petroleum hydrocarbon impact to soil is not fully characterized southeast of the site • GRO (52,000 gg/L to 110,000 µg/L) and BTEX (benzene at 4,400 gg/L to 13,000 jAg/L) were reported for samples collected from newly installed wells MW-10, MW-12, and MW-15 screened within sand zone 2 Based on this observation, the lateral extent of impact to groundwater within sand zone 2 is not fully characterized southeast of the site • GRO (81 gg/L) and benzene (4 3 gg/L) were reported for the sample collected from newly installed well MW-13 Well MW-14 did not contain groundwater at the time of the June 2004 monitoring event • Soil vapors are currently being extracted from wells VW-1, VW-3, VW-4, VW-6, VW-8, VW--14, MW-7, and MW-9 As of June 7, 2004, an estimated cumulative mass of 3,801 pounds of GRO has been removed from the subsurface using SVE • P 1Bp-Arco for URS161DMeportsla 6100-ossesstnen1 scm_update doL Page 13 5 M rus