ARCHIVED REPORTS_XR0007790 - Laserfiche WebLink

Home Browse Search

i!) ill • PRIVILEGED & CONFIDENTIAL concentrations for total petroleum hydrocarbons as gasoline and diesel (TPH-g and TPH-d) and benzene, toluene, ethylbenzene and xylenes (BTEX). Total recoverable petroleum 1 hydrocarbons (TRPHs) were found at concentrations ranging from 10 parts per million (ppm) to 31 ppm, which is well below the Maximum Contaminant Level (MCL) of 100 ppm as set forth by the Regional Water Quality Control Board (RWQCB). Based on the above-mentioned analytical results, it was concluded that the on-site soil contamination, although below regulatory action levels, was likely caused by the spilling of waste oil and motor oil at the former on-site gasoline service station. There was no indication of diesel or gasoline contamination. Groundwater was expected at a depth of approximately 60 feet bgs, and was not sampled during this Subsurface Investigation. February 1997, Follow-Up Phase II Subsurface Investigation Building Analytics completed a Follow-up Phase II Subsurface Investigation in February 1997, which included the installation and testing off three monitoring wells. The following is a summary of the findings from the investigation: • The groundwater flow direction in February 1997 was measured to be to the northeast, with a hydraulic gradient of 0.0025; • TPH-g at levels up to 1,300 ppm, and benzene at levels up to 0.39 ppm, were ' reported in the soil samples collected from Boring B2, at depths between 35 and 55 feet bgs; • TPH-g and BTEX were reported in groundwater samples collected from MW-1 or MW-3; 0 Benzene was not reported in the groundwater sample collected from MW-2; o TPH-g (1.6 ppm), ethylbenzene (120 ppm) and xylenes (370 ppm) were reported ' in the groundwater sample collected from MW-2; and o Methyl-tert-butyl ether (MTBE) was not reported in any of the soil or groundwater samples collected. September 1997, Additional Phase II Subsurface Investigation and Quarterly Monitoring ' Building Analytics completed an additional Phase II Subsurface Investigation and Quarterly Groundwater Monitoring in September 1997, which included the installation of one additional 80-foot deep soil boring and groundwater monitoring well, and the monitoring and sampling of the four groundwater monitoring wells. The following is a summary of the findings from the investigation and monitoring event: • The groundwater flow direction was measured to be to the northeast with a hydraulic gradient of 0.0055; ' • TPH-g up to 75 ppm were reported in the soil samples collected from Boring B4 at depths between 35 and 45 feet bgs; + Benzene up to 0.057 ppm was reported in the soil samples collected from Boring B4 at depths between 35 and 45 feet bgs; 2 198075-WF8.SLOCktan Ph.11 and Quart-Grnundwalcr