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C A M B R I A Ms.Lori Duncan <br /> November 18,2005 <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). Aegis' <br /> June 18, 1990 Preliminary Subsurface Investigation/Tank Closure Report (Interim Soil <br /> Remediation Work Plan)summarizes this investigation. <br /> 1990 UST Upgrade Activities: During June 1990, the former USTs were removed, and Aegis <br /> collected six soil samples (TS-1 through TS-6)from beneath the USTs and six soil samples (TR-I <br /> through TR-6) beneath product lines. The highest petroleum hydrocarbon concentrations were <br /> detected in soil samples collected from the UST excavation, with maximum concentrations of <br /> 19,000 ppm petroleum hydrocarbons volatile(PHV) and 280 ppm benzene. Aegis' June 18, 1990 <br /> © Preliminary Subsurface Investigation/Tank Closure Report(Interim Soil Remediation Work Plan) <br /> summarizes this investigation. <br /> 1990 Well Installation: During July 1990, Aegis installed monitoring wells MW-1 through <br /> MW-3 and vapor extraction wells VEW-I 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 were 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 soil vapor extraction (SVE) feasibility test at the 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 <br /> petroleum hydrocarbons detected below the former UST location. Well MW-3 was selected <br /> based on previously detected separate-phase hydrocarbons (SPH) in this well. Aegis documented <br /> these activities in their January 31, 1992 Results Report for Air Monitoring of Extended Pilot <br /> Vapor Extraction Test. <br /> 1995 Geoprobe®Soil Borings: During September 1995, Fugro West, Inc. (Fugro) of Roseville, <br /> California drilled four Geoprobe soil borings (Geo-I through Geo-4). Soil samples from the <br /> boring drilled in the former UST location contained total purgeable hydrocarbons as gasoline <br /> (TPHg) concentrations up to 7,000 ppm (at 16 fbg) and a benzene concentration of 10 ppm (at <br /> 49 fbg). TPHg and benzene were not detected in soil from the other borings. Grab groundwater <br /> samples collected from these borings contained TPHg ranging from 14,000 to 60,000 ppb and <br /> benzene ranging from 4,100 to 9,800 ppb. Complete investigation results may be found in <br /> Fugro's November 29, 1995 Limited Subsurface Investigation Results. <br /> 1997 Soil Borings and Well Installation: During July 1997, Cambria drilled four on-site soil <br /> borings (SB-I through SB-4) near the dispenser islands. Petroleum constituents were not <br /> detected in soil from any of the borings except SB-2, drilled near the northeastern dispenser. <br /> 2 <br />