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Section 20937, Forward continues to install additional landfill gas extraction wells, as needed. New Historical Intrawell Maximum Values As shown in the table below, eight new historical intrawell maximum values were measured during the third quarter monitoring event. However, the three first-time VOC detections measured in well MW-17 are suspected field contaminants since similar concentrations were also measured in the QA/QC equipment blank. New Historical Intrawell Maximum Values Well Analyte New Value Previous Value MW-10 cis-1,2-DCE 0.17' g/L 0.15' g/L TCFM 0.32' /L 0.31jµg/L MW-14 Potassium I 1 mg/L 10 mg/L MW-16 PCE 0.19j gg/L 0.181µg/L MW-17 Ethylbenzene 0.17j gg/L ND Toluene 0.70 g/L ND Xylenes,total 0.92 µg/L ND MW-21 1 Chromium,hexavalent 1 0.0024 mg/L 0.0020 mg/L Notes: j—Trace value(between MDL and PQL) Concentration Limit Thresholds Data obtained during the third 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 third quarter 2007. As summarized in this table, CLs were exceeded for wells MW-IA, MW-2A, MW-3A,MW-10,MW-13,MW-14, MW-15, MW-16, MW-17, MW-18, MW-19, and MW-21. 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 November during the fourth quarter 2007 sampling event and a second independent sample will.be collected in December 2007. 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 August 17, 2007. On September 12,2007, 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 D:\2007-043\ForwardAnsfin—suMO7.doe 6 Geologic Associates