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S E C 0 R REMEDIAL PERFORMANCE SUMMARY An OS system has been operational at the site since December 2002. A summary of the operation of the OS system, and monthly groundwater sampling activities are presented in the following sections. A site plan showing the layout of the OS system is included as Figure 1. Ozone Injection Operation The OS system consists of a panel mounted KVA Associates (KVA) C-SpargeTm System that produces 4 grams per hour (0.009 pounds per hour) of ozone. During the second quarter 2005 (March 29, 2005 to June 6, 2005), ozone was programmed to be injected into 10 of the 15 OS wells (SP-2, 4, 5, 7, and 10 through15); however, the OS system was non-operational for the majority of this time period due to the circuit breaker tripping. On March 29, 2005 it was determined that the circuit breaker was faulty; a new one was installed on April 29, 2005 and the system was restarted. During the May and June 2005 site visits, the circuit breaker had been tripped, and the OS system was off-line upon arrival at the site. The manufacturer has provided a time-delayed fuse kit to address this problem. SECOR will install the fuse during the third quarter 2005. Cumulatively, the OS system has operated for 9,186 hours, and has injected a total of approximately 83 pounds of ozone into the subsurface. Table 1 presents the operating data for the OS system, and includes operating hours and pressure readings. Remediation system field data sheets are included in Attachment 2. G'rr Monthly Groundwater Sampling During the second quarter 2005, groundwater samples were collected monthly from wells MW-3 and MW-10 on April 29, 2005; and from wells MW-3 and MW-4 on May 13, 2005 and June 6, 2005. Groundwater samples were inadvertently collected from well MW-4 instead of well MW-10 due to an error in the written work scope. Groundwater samples were submitted to STL for analysis of GRO, BTEX, and MtBE by EPA Method 8260B. Results of monthly groundwater sampling events are summarized in Table 2. Remediation system certified laboratory analytical reports and chain-of-custody documentation are provided in Attachment 3. OS System Effectiveness Although the system had a low run time this quarter due to down time associated with repairing the circuit breaker and pending parts required during maintenance of the OS system in May and June 2005, the existing OS well network appears to be successfully remediating hydrocarbons dissolved in the groundwater beneath and downgradient of s the USTs in the area of well MW-10. The results of quarterly groundwater monitoring since the startup of the OS system, and the results of monthly groundwater sampling of well MW-3 indicate the presence of declining GRO and MtBE concentration trends in wells MWA through MW-5; these wells are located in the vicinity of the OS wells. Since the system was brought on-line, concentrations of MtBE have gradually declined in well MW-10 over the quarterly sampling events performed by TRC and the monthly sampling events performed by SECOR, with occasional fluctuations in concentration reported over the last year of sampling. Graphs illustrating dissolved GRO, benzene, and MtBE { = versus time in wells MW-3 and MW-10 are provided as Figures 2 and 3. SECOR will i 1AConocoPh111ips\Rela11 Siles`11195%QSR&QRPS 2005/11195 QSR&QRPS 2M.doc