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Ozone Remediation Pilot Test Work Plan San Joaquin County Public Works, Stockton, CA June 15,2015 Page 4 be monitored with a weighted tape measure while the sand is being placed and thc augers are being gradually retracted to avoid bridging. Approximately two feet of time-release bentonite pellets will be placed above the sand to form a protective seal. The bentonite pellets will be installed as the augers are retracted. A seal of neat cement will be tremied into the annulus from the bentonite seal to the ground surface and a locking traffic box will be installed at the ground surface. A typical ozone injection well construction diagram is shown on Figure 7 (Appendix A). 4.2 OZONE INJECTION SYSTEM INSTALLATION The mass flux of petroleum hydrocarbons in groundwater from the source area is approximately 0.3 pounds per day. Approximately 4 pounds of ozone are required to oxidize one pound of petroleum hydrocarbons, so the ozone requirement to halt the flux of contaminants from the source area is approximately 1.2 pounds per day. Condor proposes to install an ozone generator capable of producing at least 3 pounds of ozone per day. This injection rate should be capable of reducing the concentration of petroleum hydrocarbons in the plume beneath the site to regulatory objectives within 12 to 24 months. The ozone generator will be installed near the Solid Waste Division building on the north side of the dispensers. The location for the ozone generator and the routing of the Teflon tubing from the ozone generator to the ozone injection wells will bc determined based on actual well location and the availability and size of the ozone generator. The Teflon tubing will be installed in PVC pipe that will be buried approximately 12 inches below the ground surface. The ozone generator is expected to be installed in an enclosed trailer to provide security and to enable cooling of the equipment with an air conditioner during the summer months. The ozone generator will be equipped with an ambient ozone detector that will shut down the system if there is an ozone leak within the trailer. 4.3 OPERATION AND MAINTENANCE OF THE OZONE INJECTION SYSTEM The ozone generator will have solenoids to control the flow of ozone to each injection well. Ozone will be injected into one well at a time. The length of time that ozone is injected into each well will be adjusted so that the wells in the areas of the plume with the highest concentrations will have ozone injected for a longer time period. The injection of ozone will be cycled through each of the wells, and then the injection cycle will be repeated. The operation of the ozone generator will be monitored on a monthly basis, unless conditions indicate more frequent monitoring is required. Maintenance will be performed on the ozone generator in accordance with the manufacturer's recommendations. 4.4 MONITORING POTENTIAL IMPACTS TO GROUNDWATER There is a potential for ozone injection to mobilize arsenic in groundwater and to oxidize chromium HI to hexavalent chromium. To monitor these potential impacts, groundwater samples collected from the monitor wells during quarterly monitoring events at the site will be analyzed for arsenic, total chromium, and hexavalent chromium in addition to the standard analyte suite for the site. During the groundwater monitoring event prior to system startup, groundwater samples collected from the monitor wells will be analyzed for arsenic, total chromium, and hexavalent chromium to provide background data prior to the installation and startup of the ozone injection system. 4.5 LABORATORY ANALYSES The groundwater samples collected from the monitoring wells are currently analyzed for TPI-I-G, benzene, toluene, ethyl benzene, and total xylenes (BTEX) and MTBE by EPA Method 8260B; each sample collected in two 40 milliliter glass VOAs with hydrochloric acid preservative and a 14 day hold CONDO