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beneath the site. Three of the soil borings were completed as groundwater monitoring wells (MW1 through MW3) and two of the soil borings were completed as vapor extraction wells (VW1 and VW2). On March 24 and 25, 1998, ATC personnel supervised advancement of seven soil borings at the site (ASB1, MW41 MWS, MW6, MW7, S138, and S139) to depths ranging from approximately 26.5 to 62 feet bgs. These borings were advanced to evaluate the horizontal and vertical extent of petroleum hydrocarbon impacted soil and groundwater; evaluate and refine soil stratigraphy; and install groundwater monitoring wells MW41 MW5, MW6, and MW7 within the uppermost aquifer. In November 1999, ATC personnel supervised the advancement of three soil borings, SB9A1 SB101 and S1311. Borings SB10 and SB11 were advanced to 46 feet bgs using hollow stem auger drilling methods and S139A was advanced to 65 feet bgs using continuous core methods. In March 2000, ATC personnel conducted remediation pilot testing activities at the site. The purpose of these tests was to evaluate vapor extraction and air sparging as viable remedial options to treat impacted soil and groundwater beneath the site. Specifically this included evaluation of whether vapor extraction could sufficiently capture air sparge off -gas, evaluation of short-term VOC flux rates, and collection of data to design a vapor extraction/air sparge system. In December 2001, an ATC geologist supervised the installation of groundwater monitoring wells MW8 through MW10, soil vapor extraction wells VW3 and VW4, and air sparge (AS) wells ASI and AS2. Five additional soil borings (SB12 through S1316) were advanced to depths of approximately 25 feet bgs. ATC implemented remedial activities at the site in December 2003. The remedial activities consisted of SVE coupled with air sparging. The SVE system was designed to utilize up to five extraction wells (VW1 through VW4 and MW1) and the AS system was designed to utilize up to two AS wells (AS1 and AS2). The SVE system consisted of a 300 actual cubic feet per minute (acfm) thermal oxidizer. The AS system consisted of a GAST 2567-P132-T908X rotary vane, 2 -horsepower, air compressor. This blower was capable of injecting at a maximum of 20 pounds per square inch (psi) at low flow rates. The maximum flow rate was approximately 21 standard cubic feet per minute (scfm). Accumulated groundwater from the extraction wells was treated and discharged to the City of Stockton sewer system. In June 2009, ATC advanced two soil borings (SB17 and SB18) to collect soil samples from the impacted saturated zone, collected groundwater samples from three of the on-site groundwater monitoring wells (MW1, MW4, and MW7), and conducted a bench scale study for ozone injection at the site. Based on the results of the bench scale study, the injection of ozone to remediate impacted soil and groundwater beneath the site was considered to be a suitable remedial alternative. During December 2010 to January 2011, ATC conducted a 30 -day ozone injection pilot test. The ozone injection pilot test consisted of continuous injection of ozone into remediation wells AS1 and AS2, alternating between ASI and AS2 at 25 minutes intervals. Target analyte concentrations were observed to decrease in groundwater samples associated with MW1 and MW3. Secondary effects to groundwater indicate that the application of this remedial approach should not cause further degradation of groundwater quality with respect to bromide, bromate, and hexavalent chromium. Ozone appeared to be a viable remedial technology for the site. Field activities and analytical results were detailed in ATC's Ozone Injection Feasibility Study dated April 8, 2011. 21 Page