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Mr.M. Scott Mansholt—CEMC Fourth Quarter 2006 Groundwater Monitoring and Sampling Report and Annual Summary Report January 12,2007 US Can-Welty Road Page 7 of 8 Most of the quarterly results for TPHd at WFSMW-1 exceeded the WQO(100 pg/L) for TPHd. Well MW-3 was only sampled during the first and fourth quarters of 2006 because of insufficient groundwater volume in the well during sampling events. TPHd concentrations detected at MW-3 have historically elevated, as was observed during first quarter 2006(1,000µg/L),but decreased substantially during the fourth quarter 2006 to 60µg/L(Table 2). TPHd were detected for the first time at MW-5 (77 pg/L). Low PAH concentrations were detected in wells MW-3 and WFSMW-I during 2006 (Table 3). All PAH concentrations during 2006 were below the most conservative WQOs and ESLs with the exception of the first quarter detection of benzo(b)fluoranthene(0.03 pg/L) at MW-3. The ESL for benzo(b)fluoranthene is 0.029µg/L. A distribution map for 2006 of petroleum in groundwater is presented as Figure 4. TPHg and TPHd have been detected in the SPO from MW-2. Well MW-2 had measurable SPO in the past and currently has a sheen and a petroleum odor. SPO has been observed in wells MW-I and MW-2, and oleophilic socks are currently used in those wells to extract the SPO. Approximately 0.21 gallon has been extracted by the oleophilic sock in MW-1, and 0.01 gallon from MW-2. An oleophilic sock was placed in MW-2 during the fourth quarter of 2005. A summary of the SPO thickness measurements is presented in Table 1. CONCLUSIONS AND RECOMMENDATIONS The groundwater elevation and gradient remained relatively consistent during 2006. The groundwater elevation varied between 69.63 and 72.66 feet above MSL with a gradient predominantly toward the east at 0.001 ft/ft. Dissolved-phase TPHg and BTEX do not appear to be present beneath the site. While dissolved-phase TPHd concentrations fluctuated between non- detect levels to 1,000 pg/L,the concentrations appear stable within the range of fluctuation with the possible exception of well WFSMW-1. TPHd concentrations in WFSMW-I should continue to be monitored for a possible upward concentration trend. PAH concentrations remained stable and low. SPO has been observed in wells MW-1 and MW-2 since 1999, and a total of 0.22 gallon has been extracted from these wells. SAIC recommends reducing the groundwater monitoring and sampling of the site wells to a semi- annual schedule and removing TPHg and BTEX from the analytical suite. The dissolved-phase petroleum hydrocarbons appear to be stable and not migrating. TPHg and BTEX do not appear to be affecting groundwater because these constituents have not been detected in groundwater samples collected from site wells that do not contain SPO. SAIC is preparing a work plan to properly destroy wells MW-3 and MW-4 because the water volumes in these wells are insufficient for adequate sample collection. The work plan for additional site characterization and well destruction will be submitted during the first quarter of 2007. Oleophilic socks in wells MW-1 and MW-2 will be monitored quarterly and replaced as necessary. When the petroleum sheen has been removed, SAIC recommends that wells MW-1 and MW-2 be incorporated into the monitoring and sampling program.