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Ms.Amy Terrell <br /> April 27,2010 <br /> Page 6 of 10 <br /> o Ammonia—MW-7 <br /> Dissolved phase ammonia was observed to be 63 mg/L. There is currently no <br /> established MCL for ammonia. Ammonia concentrations have fluctuated between <br /> 40.6 mg/L and 64 mg/L in groundwater samples collected from well MW-7 since <br /> 2007. <br /> 0 1,2,3-TCP—MW-7 <br /> Dissolved phase 1,2,3-TCP was observed to be 0.43 µg/L. This concentration exceeds <br /> the California Notification level of 0.005 µg/L. Dissolved phase 1,2,3-TCP <br /> concentrations have fluctuated between 0.26 µg/L and 2.3 pg/L in groundwater <br /> collected from well MW-7 since 2007. <br /> 0 1,2-DCP—MW-7 <br /> Dissolved phase 1,2-DCP was observed to be 29 pg/L. This concentration exceeds the <br /> MCL level of 5 µg/L. Dissolved phase 1,2-DCP concentrations have fluctuated <br /> between 18 pg/L and 47µg/L in groundwater collected from well MW-7 since 2007. <br /> o Diuron—MW-7 <br /> Dissolved phase diuron was observed to be 2.3 µg/L. This concentration does not <br /> exceed the EPA IRIS reference dose for drinking water (14 µg/L). Dissolved phase <br /> diuron concentrations have fluctuated between 1 µg/L and 2.3 µg/L in groundwater <br /> collected from well MW-7 since 2007. <br /> 0 1-Chloropropane—MW-7 <br /> Dissolved phase 1-chloropropane was observed to be 0.9 µg/L. There is currently no <br /> established MCL for 1-chloropropane. <br /> • Since August 2006, well MW-3, located in the vicinity of the former tank farm(Figure 2), has <br /> only contained detectable concentrations of TON and ammonia above the laboratory reporting <br /> limit (with the exception of diuron). Historical results for these COC are tabulated in Table 5 <br /> and graphically presented on Figure 7. Well MW-3 is located outside of any pilot treatment <br /> areas. A dissolved phase diuron concentration of 1.5 pg/L was detected in the groundwater <br /> sample collected from well MW-3 during the March 2010 groundwater sampling event. This <br /> diuron concentration is below the EPA IRIS reference dose for drinking water(14µg/L). <br /> Downgradient—MW-5 <br /> Well MW-5 is located approximately 43 feet east (downgradient) of the Off-site Expanded Pilot Test <br /> plot in the Welty Road right-of-way (Figure 2). Dissolved phase COC concentrations detected at well <br /> MW-5 are generally lower compared to on-site wells. Historical results for MW-5 are tabulated in <br /> Table 5 and graphically presented on Figure 10. <br />