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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 AS1 and AS2. Five additional soil borings (SB12 through 5616) were advanced to depths of approximately 25 feet bgs. Well construction details are provided in Table 1. ATC implemented remedial activities at the site in December 2002. The remedial activities consisted of soil vapor extraction (SVE) coupled with air sparging (AS). 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 capable of injecting at a maximum of 20 pounds per square inch (psi) at low flow rates with a maximum flow rate of 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. ATC shut the SVE/AS system down on April 28, 2009. In June 2009, ATC advanced two soil borings (SB17 and S1318) 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, injection of ozone to remediate impacted soil and groundwater beneath the site was considered to be a suitable remedial alternative. Between December 2010 and 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 AS1 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 indicated 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. In electronic correspondence dated February 10, 2012, the San Joaquin County Environmental Health Department (SJCEHD) provided authorization to begin ozone injection. On February 29, 2012, ozone injection was initiated utilizing a portable ozone injection system that was installed at the site. On March 9, 2012, the ozone injection system was shut off pending approval from the RWQCB in the form of a Monitoring and Reporting Plan (MRP). Approximately 8.91 pounds of ozone was injected into the groundwater from February 29 to March 9,2012. On April 24 and May 1,2012, pursuant to requests from the RWQCB,ATC submitted a Notice of Intent and a draft MRP to the RWQCB. On Monday,April 30,2012, it was discovered that the portable ozone injection system had been stolen from the site during the previous weekend. In electronic correspondence dated May 1, 2012,the RWQCB issued an edited version of the draft MRP and indicated ozone injection could commence at the site provided conditions in the draft MRP are followed and upon receipt of final approval from the SJCEHD.