ARCHIVED REPORTS_20100427 ATC 1Q2010 GWMR COMPLETE

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Ms.Amy Terrell April 27,2010 Page 4 of 10 • Historical groundwater elevations and COCs for well MW-2 are presented in Table 3 and Table 5, respectively. Graphical representations of this data are plotted versus time on Figure 6. o Nitrate/Nitrate as Nitrogen, Total Oxidizable Nitrogen (TON)—MW-2 The TON concentration was observed to be 0.547 milligrams per liter (mg/L). The TON concentration was significantly less compared to the third quarter 2009 (58.9 mg/L) event. Prior to the 2002 Remediation Pilot Study, dissolved phase TON concentrations were reportedly greater than the California Maximum Contaminant Level (MCL) of 10 milligrams per liter (mg/L). Subsequent to the 2002 Remediation Pilot Study, TON concentrations were observed to decrease to concentrations below the MCL, and in some cases, below the laboratory reporting level. This decreasing TON trend was observed through August 2006. Since August 2006, TON concentrations have been steadily increasing in well MW-2. o Ammonia—MW-2 The dissolved phase ammonia concentration was observed to be 43.4 mg/L. There is currently no established MCL for ammonia. Dissolved phase ammonia concentrations have generally been decreasing since the 2002 Remediation Pilot Study. 0 1,2,3-trichloropropane (1,2,3-TCP)—MW-2 The dissolved phase 1,2,3-TCP concentration was observed to be 0.38 micrograms per liter (gg/L). 1,2,3-TCP concentrations have generally been decreasing subsequent to the 2002 Remediation Pilot Study. This 1,2,3-TCP concentration exceeds the California Notification Level of 0.005 µg/L. 0 1,2-dichloropropane (1,2-DCP)—MW-2 The dissolved phase 1,2-DCP concentration was observed to be 9.3 gg/L. This concentration exceeds the MCL of 5 µg/L. Since the Remediation Pilot Study was initiated in 2002, dissolved phase 1,2-DCP concentrations have been decreasing slightly (Figure 6). Subsequent to the 2007 Expanded Pilot Test, no significant change in 1,2-DCP trends were observed. Prior to 2002, dissolved phase 1,2-DCP concentrations reportedly had significant seasonal fluctuations. Since 2002, seasonal variation in dissolved phase 1,2-DCP concentrations have not been observed. 0 1,2-dibromo-3-chloropropane (DBCP) and 1,2-dibromoethane (EDB)—MW-2 Dissolved phase DBCP and EDB concentrations have not been detected above the laboratory reporting limit since third quarter 2003 and first quarter 2004, respectively. o Diuron—MW-2 Dissolved phase diuron was detected at a concentration of 10 pg/L, which is similar to the reported diuron concentrations between 2004 and 2009. This diuron concentration does not exceed the United States Environmental Protection Agency (EPA) Integrated