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Ozone Irnection Monitoring Plan i Monitoring wells MW-3 through MW-10 are used as observation wells to monitor the performance of the ozone injection system Monitoring wells MW-1 and MW-2 are used as background wells During the first quarter 2006, field parameters were collected on a monthly basis and select laboratory parameters were collected on a quarterly basis During the first quarter 2006 monitoring event, all samples were collected after purging three volumes of well casing The ozone Injection monitoring plan is listed below and a summary of frequency and significance of field and laboratory parameters is presented in Table 3 Field Parameters (Monthly) pH, Dissolved Oxygen (DO), and Specific Conductivity Laboratory Parameters (Quarterly) GRO, BTEX, five oxygenates, 1,2-DCA, EDB, ethanol, Chemical Oxygen Demand (COD), Total Iron, and Heterotrophic Plate Count Laboratory Parameters (Annually) Total Organic Carbon (TOC), Nitrates, Sulfates, Orthophosphates, and Total Dissolved Solids (TDS) Results Field and analytical parameters collected under the ozone monitoring plan and the quarterly monitoring program are presented in Tables 4 and 5 Change in DO concentrations for select observation and background monitoring wells are presented in Figure 7 The historical GRO, benzene, and MTBE concentration, and depth to water variation over time at select monitoring wells (MW-4 through MW-8) are Illustrated graphically In Figures 8 through 12 • Petroleum hydrocarbon concentrations in all the monitoring wells appear to have decreased since the operation of the ozone injection system During first quarter 2006, the GRO concentration at well MW4 appears to have decreased (from less than 2,500 pg/L to 640 µg/L) since the previous monitoring event (December 8, 2005) GRO concentrations in the remaining monitoring wells were below laboratory reporting limits during first quarter 2006, however, elevated reporting limits in the range of 100 pg/L to 5,000 µg/L were reported for wells MW-5, MW-6, and MW-8 The benzene concentration at well MW4 appears to have decreased (from less than 25 pg/L to 5 5 gg/L) since the previous monitoring event (December 8, 2005) Benzene concentrations in the remaining wells were not reported above laboratory method detection limits during the first quarter 2006 The MTBE concentrations at wells MW-4 and MW-10 appear to have decreased, while the MTBE concentrations at wells MW-1, MW-3, MW-5, MW-6, MW-8, and MW-9 appear to have Increased since the previous monitoring event The greatest decrease in MTBE concentration was observed at well MW4 (from 2,800 pg/L to 880 pg/L) while the greatest Increase was observed at well MW-6 (from 2,300 µg/L to 5,700 pg/L), since the previous monitoring event During the first quarter 2006, the DO levels in observation wells (MW-3 through MW-10) varied in the range of 0 9 mg/L to 9 2 mg/L, while the DO levels in background monitoring wells (MW-1 and MW-2) were in the range of 0 9 mg/L 6 2 mg/L The DO levels In the observation wells continue to be generally greater than the background monitoring wells, and is likely due to ozone injection DO levels in the observation wells are consistent with levels measured during previous monitoring events The COD concentrations generally appear to correspond to changes in GRO concentrations for wells MW-4, MW-6, and MW-8 (Figures 13 through 15) Inorganic constituents such as total Iron, nitrates, and sulfates generally appear to be influencing the heterotrophic plates counts in the groundwater (Figures 16 through 18) K\13p-Arco for URS154691Quarterly120061Arco_5469_1 Q06 docPage 5 of 6 srKAW5