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PRIVILEGED&CONFIDENTIAL • Benzene at concentrations of up to 0.057 ppm was reported in the soil samples collected from Boring B4,at a depth of approximately 45 feet bgs; • TPH-g and BTEX were not reported in groundwater samples collected from monitoring wells MW-1 or MW-3; • TPH-g was reported in the groundwater samples collected from MW-2 and MW-4 ' at concentrations of up to 3.4 ppm; • TPH (Carbon Range C8-C44+) was also reported in the groundwater sample collected from MW-2, at a concentration of 2.3 ppm; • Benzene was reported in the groundwater ,samples collected from MW-2 and MW-4 at concentrations of 1.2 parts per billion.(ppb) and 11 ppb, respectively; and • MTBE was not reported in the soil or groundwater samples collected. 2.5 Work Plan -.Additional Phase II Subsurface Investigation,May 1997 Subsequent to the September 1997 Additional Phase II Subsurface Investigation, the SJCEHD requested that, an additional soil boring be installed down-gradient from groundwater monitoring wells MW-2 and MW-4. Building Analytics submitted a Work Plan for the Additional Soil Boring and Quarterly Groundwater Monitoring to the SJCEHD on May 4, 1997, which was approved with comments on January 20, 1998. Final approval was.issued after the SJCEHD received reports from adjacent LUST sites on July 20, 1998. 2.6 Additional Phase. II Subsurface Investigation and Quarterly Monitoring, October 1998 R In August 1998, Building Analytics performed an Additional Phase II .Subsurface Investigation and Quarterly Groundwater Monitoring, which included the installation of one additional 80-foot deep soil boring, and the monitoring and sampling of the four existing 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 concentrations between 1.3 and 590 milligrams per kilogram (mg/kg) were reported in the soil samples collected from Boring B5 at depths between 35 and 61 feet bgs._ The deepest sample, B5-78, collected at 78 feet bgs, was reported to contain 2.8 mg/kg of TPH-g; Only sample 135-50, collected at 50 feet bgs, was reported to contain benzene, at 0.006 mg/kg. • TPH-g and BTEX were not reported in groundwater samples collected from monitoring wells MW-1 or MW-3; • TPH-g was reported in the groundwater samples collected from Boring B5, MW-2 and MW-4 at concentrations of up to 13 ppm; • Benzene was reported in the groundwater samples collected from Boring B5 and MW-4, at concentrations of 2 ppb and 8 ppb, respectively; r 3 199164-WFB.Stockton Well Abandonment Work Plan