Laserfiche WebLink
Project No SS I00-06-I 1 B <br /> April 19, 1996 <br /> ' 7.0 CONCLUSIONS AND RECOMMENDATIONS <br /> 71 Conclusions <br /> ' Based on Geocon's review of all soil and groundwater data acquired through February 1996, <br /> summarized below are conclusions regarding the environmental investigations performed at the site <br /> ' o Soil samples collected from the UST excavation indicated that releases of fuel hydrocarbons into <br /> the surrounding vadose zone soils had occurred Excavation sample UST-1 collected from the <br /> west end of the unleaded fuel UST excavation contained TPHg at a concentration of 2,000 mg/kg <br /> and excavation sample UST 2-1 collected from the east end of the diesel fuel UST contained <br /> TPHd at a concentration of 58 mg/kg <br /> 1 o Product line sample P-2, collected at 0 8 meters (2 5 feet) bgs, contained 3 5 mg/kg TPHg <br /> Petroleum hydrocarbons were not detected in vadose zone soil collected from SB-3 directly <br /> 1 beneath the former pump island, limiting the source area to the former USTs <br /> G The low concentrations of TPHg in vadose zone soils in SB-1, SB-2, MW-1, MW-2, MW-3 and <br /> ' VW-1 and the maximum TPHg concentration of 500 mg/kg detected in VW-2, located adjacent to <br /> the former pump island and UST excavation, at 14 0 meters (46 feet) bgs indicate that a vadose <br /> zone soil plume exits beneath the former USTs <br /> G The vadose zone soil plume bounded by SB-1, SB-2, MW-1, MW-2, MW-3 and VW-1 has an <br /> approximate volume of 1,500 cubic yards <br /> ' G The location of the central portion of the vadose soil plume is in the vicinity of VW-2, but has not <br /> been identified Consequently, the concentration of TPHg impacted soil and the resulting mass of <br /> TPHg cannot be estimated <br /> 0 Groundwater exits beneath the project boundaries at a depth of approximately 18 6 meters (61 <br /> ' feet)bgs with a general flow direction towards the west at a gradient of 0 001 <br /> o Groundwater quality data indicates that dissolved TPHg, benzene, and MTBE exist beneath the <br /> ' site at maximum reported concentrations of 16,000 ug/L TPHg, 3,000 ug/L benzene, and 170 <br /> ug/L MTBE, respectively <br /> ' o Benzene concentrations are in excess of the California Maximum Contaminant Level (MCL) of <br /> 10 ug/L <br /> 12 <br />