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I I . During first quarter 2003 (between January 9, 2003 and March 17, 2003), Stratus technician conducted eleven site visits to collect field parameters and laboratory parameters. Field data sheets presenting field parameters collected between January 9, 2003 and March 17, 2003 are included in Appendix A, and certified analytical reports with chain-of-custody documentation are included in Appendix C. On March 17, 2003, the ozone injection system was observed non-functional. Based on hour meter readings recorded for March 11 and March 17, 2003, the C-Sparge'"" system likely shutdown on March 12, 2003. On March 17, 2003, upon identifying that there was no power supply to the C-SpargeTM system, Stratus technician's attempt to re-start the system by re-setting the power supply and was not successful. Stratus in co-ordination with C-Sparge'"' panel manufacturer (KVA®) identified the problem to be associated with a solenoid valve. The ozone injection will be re-started after replacing the solenoid valve during the second quarter 2003. Monitoring Plan Monitoring wells MW-3 through MW-10 are used as observation wells to monitor the performance of ozone injection system. Monitoring wells MW-1 and MW-2 are used as background wells to evaluate and monitor for natural geo-chemical changes in groundwater. The following field and laboratory parameters will be monitored periodically to evaluate and optimize the performance of the ozone injection system. Field Parameters: pH, Dissolved Oxygen (DO), and Specific Conductivity Laboratory Parameters: TPHG, BTEX, Chemical Oxygen Demand (COD), Ferrous Iron, Total Organic Carbon (TOC), DO, and Oxidation Reduction Potential (ORP) During first quarter 2003, field parameters were collected on a weekly basis and laboratory parameters 0 were collected on a monthly basis. Beginning second quarter 2003, the sampling frequency for field parameters will be changed to bi-monthly and the sampling frequency for laboratory parameters will be changed to quarterly. TPHG, BTEX, and oxygenates will also be analyzed as a part of regular quarterly monitoring program. Table 3 presents the revised sampling frequency, field and laboratory parameters analyzed, and significance of both lab& field parameters. Under the ozone injection monitoring plan, groundwater samples for laboratory analysis were collected without purging. However, groundwater monitoring samples collected as part of the quarterly monitoring program (including the wells listed as observation wells)were collected after purging. Results Results of field and analytical parameters collected to date to evaluate and optimize the performance of ozone injection system are presented in Tables 4 and 5. Field Parameters pH Prior to the C-Sparge'"" system start-up (December 11, 2002), pH measured in onsite monitoring wells (MW-1 through MW-10) were in the range of 6.20 to 7.4. During the operation of ozone injection system (between January 9 and March 17, 2003), pH levels in onsite monitoring wells were in the range of 6.28 to 10.14. A consistent trend of pH variation either correlating to petroleum hydrocarbon concentrations or to natural variation (observed in background monitoring wells)could not be identified. PA1Bp-Arco for URS154691Quartcrly120031Arco_5469_1 Q03.doc 57RATV5