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Ms Margaret Lagono S E C 0 R April 28, 2005 Page 4 . During the first quarter 2005 monitoring and sampling event, the following maximum concentrations were reported TPHg 470 micrograms per liter (pg/L) (MW-16) (TRC 10'05 Quarterly Monitoring Report [QMR]) Benzene 18 pg/L (MW-4) (TRC 1 Q'05 QMR) MtBE 18 pg/L (MW-16) (TRC 1Q'05 QMR) TPHg, benzene, and MtBE concentrations in groundwater continue to decline REMEDIATION STATUS The ozone infection system consists of panel mounted KVA C-SpargeTM system that produces 4 grams of ozone per hour (0 009 pounds per hour) The system injects to 10 sparge points (SP4 through SP13) During the current quarter (December 30, 2004 through March 22, 2005), the system was down due to a number of reasons In January, the system was down due to broken lines in 5 of the 10 wells In February, the lines were all repaired and the system was reprogrammed and restarted During the March site visit, it was discovered that the system had shut down soon after start up in February due to a tripped ozone sensor When the system was restarted in March, a leak in the hose running from the compressor to the manifold was discovered The system is shut down until the hose can be repaired (System data is presented in Table 1) The performance of the ozone infection system is evaluated by the results of monthly and quarterly groundwater sampling Monthly groundwater samples were collected from monitoring wells MW-16 and VW-7 on January 28, February 11, and March 22, 2005 and analyzed for TPHg, BTEX compounds, and MtBE Results of monthly groundwater sampling events are summarized in Table 2 Concentration versus time graphs for dissolved TPHg, benzene, and MtBE in monitoring wells MW-16 and VW-7 are provided in Figures 2 and 3 REMEDIATION SYSTEM CRITICAL EVALUATION Based on the results of the first quarter 2005 data (both groundwater monitoring and remediation system operational data) ozone sparging continues to be effective in reducing petroleum hydrocarbon concentrations Dissolved MtBE and other hydrocarbon levels have declined over time since ozone sparge system startup in 2001 (as shown in Figures 2 and 3) CHARACTERIZATION STATUS Contamination in soil and groundwater has been adequately delineated CONCLUSION AND RECOMMENDATIONS Based on the results of the first quarter 2005, the existing ozone sparge well network appears to be successfully remediating hydrocarbons dissolved in the groundwater at