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[1 <br /> C A M B R I A <br /> investigation is summarized in Aegis' June 18, 1990 Preliminary Subsurface InvestigationlTank <br /> Closure Report (Interim Soil Remediation Work Plan) <br /> 1990 UST Upgrade Activities During June 1990, the former USTs were removed, and Aegis <br /> collected six soil samples from beneath the US Ts and six soil samples beneath product lines The <br /> highest concentrations of petroleum hydrocarbons were detected in soil samples collected from the <br /> UST excavation with maximum concentrations of 19,000 ppm petroleum hydrocarbons volatile <br /> (PHV) and 280 ppm benzene This investigation is summarized in Aegis' June 18, 1990 <br /> Preliminary Subsurface InvestigationlTank Closure Report (Interim Soil Remediation Work <br /> Plan) <br /> 1990 Well Installation During July 1990, Aegis installed monitoring wells MW-1 through MW-3 <br /> and vapor extraction wells VEW-1 and VEW-2 The highest concentrations of petroleum <br /> hydrocarbons detected in soil were from boring VEW-2 at 45 fbg, with 12,000 ppm PHV and <br /> 110 ppm benzene During the initial groundwater monitoring event, PHV and benzene were <br /> detected in all wells at concentrations ranging from 350 to 500,000 parts per billion (ppb) and <br /> 1 90 to 10,000 ppb, respectively These results are discussed in Aegis' January 4, 1991 Site <br /> Assessment Report <br /> 1991-1992 Vapor Extraction Feasibility Test During late 1991 and early 1992, Aegis performed <br /> a 75-day vapor extraction feasibility test at the subject site using wells VEW-1, VEW-2, and <br /> MW-3 Wells VEW-1 and VEW-2 were tested to evaluate their feasibility for removing petroleum <br /> hydrocarbons detected below the former UST location Well MW-3 was selected based on <br /> previously detected separate-phase hydrocarbons (SPH) in this well Aegis documents these <br /> activities in their January 31, 1992 Results Report for Air Monitoring of Extended Pilot Vapor <br /> Extra(tion Test <br /> 1995 Geoprobe Soil Borings During September 1995, Fugro West, Inc (Fugro) of Roseville, <br /> Calitorma drilled four GeoProbe soil borings Soil samples from the boring drilled in the former <br /> UST location contained total purgeable hydrocarbons as gasoline (TPHg) concentrations up to <br /> 7 000 ppm (at 16 tbg) and a benzene concentration of 10 ppm (at 49 fbg) TPHg and benzene <br /> were not detected in soil from the other borings Grab groundwater samples collected from these <br /> borings contained TPHg ranging from 14,000 to 60,000 ppb and benzene ranging from 4,100 to <br /> 9,800 ppb The complete results of this investigation may be found in Fugro's November 29, 1995 <br /> Limited Subsurface Investigation Results <br /> 0854 2 <br />