ARCHIVED REPORTS_XR0004073 - Laserfiche WebLink

Home Browse Search

' Pombo Property Subsurface Investigation Report Page: 9 •, from Boring B-10 at 17 feet. 0.8 mg/l gasoline range petroleum hydrocarbons, 6.2 ug/l benzene, 5.1 ug/1 toluene, 41 ug/l ethyl benzene, and 19 ug/l total xylenes, ' were detected in the groundwater sample from Boring B-11 at 23 feet. 0.8 mg/1 gasoline range petroleum hydrocarbons, 6.2 ug/1 benzene, 5.1 ug/l toluene, 41 ug/l ethyl benzene, and 19 ug/1 total xylenes, were detected in the groundwater sample from Boring B-11 at 23 feet. 0.7 mg/1 gasoline range petroleum hydrocarbons, 2.1 ug/l benzene, 4.4 ug/l toluene, 22 ug/1 ethyl benzene, and 5.5 ug/l total xylenes, were detected in the groundwater sample from Boring B-12 at 16 feet 1 Boring B-9, installed to determine the vertical extent of the contamination, ' contained 0.7 mg/1 gasoline range petroleum hydrocarbons, 2.1 ug/1 benzene, 4.4 ug/l toluene, 22 ug/l ethyl benzene, and 5.5 ug/l total xylenes in a groundwater sample collected from 33 feet. MTBE was not detected at a detection limit of 1.0 ug/l. in any of the Geoprobet groundwater samples. The analytical laboratory reported non-detectable concentrations of gasoline, BTEX, and MTBE for groundwater samples collected in all three monitoring wells. 4.0 CONCLUSIONS AND RECOMMENDATIONS Contaminants of concern have been identified as gasoline range petroleum hydrocarbons; benzene, toluene, ethyl benzene, and xylenes probably sourced '�. from the former underground storage tank. MTBE has not been detected in this investigation. Limited soil and groundwater impacts by gasoline and gasoline components have been recognized. Soil contamination was confirmed in a soil sample collected from the thin shallow, confined to semi-confined, sandy unit (upper sand) in boring' B i 1` at�10_feet. Soil contamination was detected in the same thin shallow, confined to semi- confined, sandy unit (upper sand) in_boring B3 at 10 feet in the September 1998 investigation. Soil contamination has not been recognized at other sampling locations. Soil contamination appears to be restricted to the immediate vicinity of the former underground storage tank. The contamination distribution appears to be controlled by the thin shallow, confined to semi-confined, sandy unit (upper ' sand). High concentrations of groundwater contamination by gasoline and gasoline components were detected in the Geoprobe"' groundwater sample collected from boring B3 at 15 feet. Low concentrations of groundwater contamination by gasoline and gasoline components were detected in the Geoprobe groundwater ' samples collected from boring B10, B 11, and B12 at depths 16 to 23 feet and boring B9 at 33 feet. The groundwater sample collected from boring B3 at 15 feet was collected from within the thin shallow, confined to semi-confined, sandy unit ' (upper sand). The majority of the soil and groundwater contamination appears to be restricted to the thin shallow, confined to semi-confined, sandy unit (upper • sand).