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per square inch (PSI) at low flow rates. The maximum flow rate is approximately 21 standard cubic feet per minute (SCFM). Accumulated groundwater from the extraction wells is 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 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 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. In electronic correspondence dated February 10, 2012, the 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 CRWQCB 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 CRWQCB, ATC submitted a Notice of Intent and a draft MRP to the CRWQCB. 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 CRWQCB 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. On October 16 and 17, 2012, a mobile ozone injection system was re-installed at the site and ozone injection into MW1, AS1, and AS2 commenced on November 8, 2012. From November 8 through December 28, 2012, ozone was injected into the groundwater for approximately 721.85 hours resulting in approximately 90.24 pounds of ozone injected into the groundwater. Petroleum hydrocarbon concentrations decreased significantly in the groundwater samples collected from MW1, MW3, and AS2 on December 26, 2012, compared to the concentrations detected in samples collected from these wells on September 10, 2012. Petroleum hydrocarbon concentrations were not detected above MCLs in the samples collected from MW1, MW3, and AS2 on December 26, 2012. The ozone sparge system was shut down on June 6, 2013. 1.3 Visitors All visitors to the Site must be instructed about the hazards of the activities that ATC or its subcontractors are performing. All visitors must sign the ATC Visitors Log (see Appendix C). 1.4 Subcontractor Activities HASP Level III Rev. 01 - June 11,2007 2-3