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Water Quality Monitoring Report Forward Landfill well MW-2A as a result of a quantifiable concentration of diisopropyl ether (DIPE). In a ON letter dated December 18, 2014, retest results confirmed DIPE in well MW-2A and chloroform and TCFM (at trace concentrations) in one of the two retest samples collected from well MW-17A. The occurrence of DIPE in well MW-2A is not believed to be related to a release from the facility, but is believed to be related to the groundwater mounding near the entrance of the landfill due to irrigation of the landscaping. Historically, low-level concentrations of VOCs have been detected in the samples collected from the Forward Unit. On behalf of Forward Inc., GLA prepared a letter report dated February 14, 2001 (RWQCB Case No. 2209), to assess the source and potential impacts of low-level VOCs in groundwater adjacent to the Forward Landfill. The letter report concluded that the 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. Forward has continued to minimize gas related impacts to groundwater by preventing ponding of water through regular site maintenance. Furthermore, in accordance with CCR Title 27, Section 20937, Forward continues to install additional landfill gas extraction wells, as needed. Recognizing that the facility is currently in corrective action, it is proposed that well MW-2A be included as a corrective action well and placed in tracking mode to evaluate constituent organic trends in the water quality. Concentration Limit Thresholds The routine inorganic monitoring data obtained from the Forward Unit during the fourth quarter 2014 monitoring period were compared to intrawell concentration limits (CLs) established for each well. In accordance with RWQCB Order No. 135-2014-0006, CLs are updated annually, and the updated CLs are presented in Table 2-4. As summarized in Table 2-4, no CLs were exceeded during the fourth quarter 2014 monitoring period. A discussion of the CL statistical methods is included in Appendix G. The retest results for CL exceedance during the third quarter 2014 monitoring event confirmed one or more inorganic constituents at concentrations slightly above a CL for samples collected in wells MW-2A, MW-10, MW-15, MW-17, and MW-19. However, comparison of the third quarter 2014 retest results with the updated CLs indicates that none of the retest results exceeded an updated CL. 2.1.5 Vadose Zone Monitoring The current vadose-zone monitoring network at the Forward Unit consists of 10 lysimeters (seven suction lysimeters and three pan lysimeters). These lysimeter locations are shown on Figure 2-1. As shown on Table 2-5A, samples were collected from suction lysimeter LY-BG1 and pan lysimeter WMU-D01N, all other lysimeters were reported dry or had insufficient soil-pore liquid for analysis. As summarized on Table 2- 5B, two VOCs were detected (one above a PQL) in the soil-pore liquid sample collected • from pan lysimeter WMU-D01N, while no VOCs were detected in lysimeter LY-BG1. For M:\2014.0012\FA_4Q14.docx 7 1/28/2015,Rev.0