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C A M B R I A <br /> were 17,000 parts per million (ppm) low/medium boiling point hydrocarbons quantitated against <br /> a gasoline standard and 400 ppm benzene, both at a depth of 15 feet below grade (fbg) This <br /> investigation is summarized in Aegis' June 18, 1990 Preliminary Subsurface Investigation/Tank <br /> Closure Report(Interim Soil Remediation Work Plan) <br /> 1990 UST Upgrade Activittes: During June 1990, the former USTs were removed, and Aegis <br /> collected six soil samples from beneath the USTs and six soil samples beneath product lines <br /> The highest concentrations of petroleum hydrocarbons were detected in soil samples collected <br /> from the UST excavation with maximum concentrations of 19,000 ppm petroleum hydrocarbons <br /> volatile (PHV) and 280 ppm benzene This investigation is summarized in Aegis' June 18, 1990 <br /> Preliminary Subsurface Investigation/Tank Closure Report (Interim Soil Remediation Work <br /> Plan) <br /> 1990 Well Installation During July 1990, Aegis installed monitoring wells MW-1 through <br /> MW-3 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 /> 190 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 <br /> performed a 75-day vapor extraction feasibility test at the subject site using wells VEW-1, <br /> VEW-2, and MW-3 Wells VEW-1 and VEW-2 were tested to evaluate their feasibility for <br /> removing petroleum hydrocarbons detected below the former UST location Well MW-3 was <br /> selected based on previously detected separate-phase hydrocarbons (SPH)in this well <br /> 1995 Geoprobe' Soil Borings: During September 1995, Fugro West, Inc (Fugro) of Roseville, <br /> California drilled four GeoProbe soil borings Soil samples from the boring drilled in the <br /> former UST location contained total purgeable hydrocarbons as gasoline (TPHg) concentrations <br /> up to 7,000 ppm (at 16 fbg) and a benzene concentration of 10 ppm (at 49 fbg) TPHg and <br /> benzene were not detected in soil from the other borings Grab groundwater samples collected <br /> from these borings contained TPHg ranging from 14,000 to 60,000 ppb and benzene ranging <br /> from 4,100 to 9,800 ppb The complete results of this investigation may be found in Fugro's <br /> November 29, 1995 Limited Subsurface Investigation Results <br /> 0854 2 <br />