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sporadic detection of low-level VOCs in groundwater(and lysimeter samples) at the Forward Unit are most likely due to landfill gas from unlined unit WMU-B. The particular VOCs detected in samples during the current monitoring period appear to support this conclusion. Forward has continued to minimize gas related impacts to groundwater by limiting interim fill areas that promote ponding of water. Furthermore, in accordance with CCR Title 27, Section 20937, Forward continues to install additional landfill gas extraction wells, as needed, and make adjustments to the LFG wells. New Historical Intrawell Maximum Values As shown in the table below, five new historical intrawell maximum values were measured during the first quarter 2011 monitoring event, including one first-time VOC detection in the sample collected from well MW-2A. New Historical Intrawell Maximum Values Well Analyte New Value Previous Value MW-2A Isopropyl Ether 0.93' gg/L Not Detected MW-22 Sulfate 131 m 116 m MW-23R Chromium,Hexavalent 9 L 8.8 jig/l, MW-24 Chloride 68.4 mg/L 68.1 m Sodium Notes:j-Trace concentration(between the MDL and PQQ. Concentration Limit Thresholds Data obtained during the first quarter 2011 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 first quarter 2011. As summarized in this table, CLs were exceeded for sulfate at wells MW-10, MW-13, MW-15,MW-18, and MW-22; and for hexavalent chromium at background well MW-23R. In accordance with the RPCMP, only wells with CL exceedances of impact constituents(as defined in Table 5-3 of the RPCMP) need to be resampled. Since all of the CL exceedances were for non-impact constituents (arsenic,bicarbonate,hexavalent chromium, nitrate as nitrogen, and sulfate)retesting is not required. 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—25 inches of mercury on February 23,2011. On March 15, 2011, the lysimeters were again checked and positive pressure was applied to evacuate the accumulated sample. As recorded in the field notes for lysimeters (Appendix Q and summarized on Table 2-5, all lysimeters were reported dry, and as a result, no soil-pore liquid samples were collected during the current monitoring period. DA20II_0050kFA_IQI I.doex 6 Geologic Associates