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PRIVILEGED&CONFIDENTIAL t • Total recoverable petroleum hydrocarbons (TRPHs) were found at concentrations ranging from 10 parts per million (ppm) to 31 ppm, which is well below the anticipated regulatory limit of 100 ppm. Based on the above-described 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. 2.3 Follow-Up Phase II Subsurface Investigation,February 1997 LBuilding Analytics completed a Follow-up Phase II Subsurface Investigation in February 1997, which included the installation and sampling of three .groundwater 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 of up to 1,300 ppm, and benzene at levels of 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 not reported in groundwater samples collected from MW-1 or MW-3; • Benzene was not reported in the groundwater sample collected from MW-2; • TPH-g (1.6 ppm), ethylbenzene (120 ppm) and xylenes (370 ppm) were reported in the groundwater sample collected from MW-2; and • Methyl-tert-butyl ether (MTBE) was not reported in any of the soil or t groundwater samples collected. Based on the above-described analytical results, it was concluded that soil and ' groundwater beneath the site had been impacted by TPH-g and BTEX in the area of groundwater monitoring well MW-2. 2.4 Additional Phase II Subsurface Investigation and Quarterly. Monitoring, September 1997 '; Building Analytics completed an Additional Phase II Subsurface Investigation and L` Quarterly Groundwater Monitoring in September and October 1997, which included the installation of one additional 80-foot deep soil boring and groundwater monitoring well Ll (in the area of well MW-2), and the monitoring and sampling of the one new and three existing groundwater monitoring wells. The following is a summary of the findings from the investigation and monitoring event: 'i • The groundwater flow direction was measured to be to the northeast with a L hydraulic gradient of 0.0055; • TPH-g at concentrations of up to 75 ppm was reported in the soil samples collected from Boring B4, at depths between 35 and 45 feet bgs; 2 199164—WFB,Stockton Well Abandonment Work Plan