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New Historical Intrawell Maximum Values As shown in the table below, 10 new historical intrawell maximum values were measured during the fourth quarter 2007 monitoring event. New Historical Intrawell Maximum Values Well Analyte New Value Previous Value MW-3 Calcium 150 mg/L 120 mg/L Chloride 170 mg/L 120 mg/L Magnesium 80 mg/L 58 mg/L Sodium 100 mg/L 86 mg/L MW-16 Bicarbonate 950 mg/L 940 mg/L MW-23R Nitrate-N 32 mg/L 30 mg/L Sodium 100 mg/L 97 mg/L Strontium 1.6 mg/L 1.3 mg/L Sulfate 280 mg/L 220 mg/L Total Dissolved Solids 1200 mg/L 995 mg/L Concentration Limit Thresholds Data obtained during the fourth quarter 2007 monitoring period were compared to concentration limits (CLs) as specified in the RPCMP for the Forward Landfill. CLs were calculated by Herst& Associates and are included in Appendix D. Table 2-4 summarizes CLs that were exceeded in samples collected from groundwater monitoring wells during the fourth quarter 2007. As summarized in this table, CLs were exceeded for wells MW-IA, MW-2A, MW-3, MW-10, MW-13, MW-14, MW-15, MW-16, MW-17, MW-18, MW-19, MW-21, and MW-23R. In accordance with the RPCMP, wells with CL exceedances (other than arsenic,bicarbonate,hexavalent chromium, nitrate as nitrogen, and sulfate, which the RPCMP do not consider impact constituents) will be resampled in February during the first quarter 2008 sampling event and a second independent sample will be collected in March 2008. The results of the retesting events will be submitted to DTSC and RWQCB under separate cover. 2.1.5 Vadose Zone Monitoring The current vadose-zone monitoring network at the Forward Unit consists of 17 lysimeters. The lysimeter locations are shown on Figure 2-1. Each accessible lysimeter was inspected and vacuums were reset to approximately—5 to—25 inches of mercury on November 8, 2007. On December 13, 2007, the lysimeters were again checked and positive pressure was applied to evacuate the accumulated sample. As recorded in the field notes for lysimeters (Appendix C) and summarized on Table 2-5, lysimeters E-2, W-2, LY-A, and LY-BG 1 had a sufficient volume of soil-pore liquid for sample collection. However, due to the limited sample volumes, lysimeter samples were only analyzed for select general chemistry constituents and/or VOCs. As shown in Table 2-6, D:\2007_0043\Forward Austin_4QO7.doc 6 Geologic Associates