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Stantec Site History and Previous Investigations Stockton Charter Way Commingled Plume No. CP0057 November 15, 2011 31, and 28 mg/kg, respectively. Following UST removal, the facility was demolished. These activities are summarized in the EMCON Results of Underground Storage Tank Removal and Overexcavation Activities dated August 5, 1996. In April and May 1996, EMCON observed ACES as they aerated approximately 300 cubic yards of hydrocarbon-impacted soil. These activities are summarized in the EMCON Completion of Soil Aeration Program dated May 20, 1996. The current property owner; Mr. Bill Halverson, constructed a car wash on the property in 2005. ARCO was asked by the owner to destroy MW-4 to make way for the new car wash. ARCO coordinated the well destruction activities to occur during property development. ARCO took advantage of these activities to coordinate the installation of a remediation system. SVE was conducted between January 1997 and February 1998 to remediate the vadose zone. SVE was terminated after an estimated mass of approximately 10,000 pounds (Ibs) (approximately 1,600 gallons) of TPHg were removed and influent benzene concentrations were less than the laboratory method reporting limits (MRL) of 0.5 milligrams per cubic meter. These activities are summarized in the Pinnacle Environmental Solutions of Cameron Park, California Results of Soil Vapor Extraction Assessment dated April 8, 1998. An AS/SVE system was installed in 2006 and was operated until December 1, 2010. The SVE system consisted of 22 wells (AEW-1 through AEW-17, AVW-1, AVW-7, AVW-8, AVW-10, and AVW-11), a 15-horsepower (hp) vacuum blower, and a 200 cubic ft per minute (cfm) H2 Oil Recovery electric oxidizer (Model H2 CO). The 15-hp vacuum blower extracted and routed soil vapors from the SVE wells into the H2O Oil Recovery electric oxidizer. Liquid condensate from the extracted soil vapor was separated from the stream using a vapor-liquid separator and was stored into a 250-gallon holding tank. The extracted soil vapors were treated using the electric oxidizer and were emitted into the atmosphere under San Joaquin Valley Air Pollution Control District Permit No. N-7375-1-0. The AS system consisted of 22 sparge wells (ASP-1 through ASP-22) and a 20-hp Rietschle Thomas compressor (Model DLR 300). The 20-hp compressor routed ambient air into each of the sparge wells. The AS system was started in January 2007, but was shut down due to a hosing failure in the process line. After retrofitting the AS system manifold with galvanized steel material and adding a post-blower heat exchanger, the AS system was restarted on March 18, 2008 and was operated until 2010. The AS/SVE system recovered approximately 4,074.20 lbs of TPHg, 8.91 lbs of benzene, and 35.88 lbs of MTBE during its total 18,896 hours of operation, which included periods of pulse mode operation. Chevron Facility#9-2033 Chevron operated the station until 1995, when the property was sold to a private dealer and has continued to operate as a Chevron-branded station. In March 1995, Groundwater Technology, Inc. of West Sacramento, California (GTI) installed three groundwater monitoring wells (MW-1 through MW-3) and one soil boring (SB-1) on the Stockton Charter Way Site History and Previous Investigations.doc 3