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As shown in Figure 6, the vapor influent contaminant concentrations, for the reporting period between March I0 and July 16, 2003, were on a steady decreasing trend from March through May In lune (coincident with the start of the 300 SCFM blower system)the vapor influent concentrations increased to concentrations observed at the beginning of the reporting period The mass removal trend (Figure 7) demonstrates that mass removal is on a steady low angle incline ' 3 3 2 Ozone Sparging System An ozone generator, enclosed in a wooden shed, injects ozone into groundwater in 19 ozone sparge ' wells (S-1 through S-19) located onsite and offsite Sparge well S-20 was not mamfolded to the system and is not used as a sparge well An ozone meter installed in the shed will shut down the ' iemediation system if the sensor detects ozone levels greater than 0 01 ppm within the shed The ozone injection manifold is set up to inject ozone for 10 minutes at a time into the sparge wells It can cycle through 10 wells at 100%the maximum injection rate, or all 20 wells (two wells at a time) ' at 50% the maximum injection rate Approximately 2 5 pounds of ozone (total for all wells) is injected into the subsurface each day The ozone sparge system delivers at a rate of 6 cfm jAfter system startup on November 26, 2002, several ozone leaks were detected at the injection manifold and were repaired O&M was performed weekly to record ozone sparge operational data ' such as ozone concentrations, hours of operation, and to check leaks at the ozone injection manifold and ozone sparge wellheads During the fourth quarter of 2002, ozone was not detected around any ozone sparge well boxes Ozone was detected in the shed housing at a maximum concentration of 0 41 ppm (December 4, 2002) The source of the leak was found and repaired No leaks have been detected since December 2002 The O&M schedule for the ozone sparge system is monthly In response to the Second Quarter groundwater analytical data, the open/closed status of the sparge ' wells was reconfigured on April 22, 2003 Each sparge well that was within the influence of the gioulidwater plume was placed in the open position,those outside of the plume were closed Oil May 27, 2003, it was observed that there was no flow registering on the ozone generator flow meter Moisture was observed in the ozone line leading from the ozone generator to the sparge pump It was also observed that the pressure relief valve in the oxygen condenser was relieving frequently ' Geocon consulted with ARCE Systems, Inc , the manufacturer of the ozone system, to correct the system ARCS indicated that the ozone generator would need maintenance that could only be performed at their shop and the oxygen condenser would have to be re-packed by the manufacturer On May 30, 2003, the ozone generator and oxygen condenser were removed and transported to ARCS in Massachusetts The re-furbished equipment is scheduled to go back on line the week of July 28, 2003 Historical operational data including well open/closed status, ozone leak detection monitoring data, and presence of an odor are presented in Table 8 SE643-00-01 -7- July 25 2003