ARCHIVED REPORTS_2016_1 - Laserfiche WebLink

Home Browse Search

C7 Water Quality Monitoring Report Forward Landfill assessment of the source and potential impacts of low-level VOCs in groundwater adjacent to the Forward Landfill. It was 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. Forward is also in the process of bringing online several inactive LFG extraction wells online in the vicinity of well MW -17. Concentration Limit Thresholds In accordance with RWQCB Order No. R5-2014-0006, the routine inorganic monitoring data obtained from the Forward Unit during the first quarter 2016 monitoring period were compared to intrawell concentration limits (CLs) established for each well. Details on the statistical analysis for the established CLs are presented in Appendix G of the fourth quarter 2014 Water Quality Monitoring Report for the Forward Landfill (GLA, 2014). As summarized in Table 2-4, the following CLs were exceeded during the first quarter 2016 monitoring period. • MW-2A—calcium, chloride, magnesium • MW-10—calcium, nitrate, total dissolved solids (TDS) • MW -13 — pH • MW -18 — bicarbonate, nitrate • MW -22 — bicarbonate In a letter dated April 18, 2016, the RWQCB was notified of these CL exceedances and retesting is scheduled for April 2015. The results of the verification sampling will be reported under separate cover. Tracking Mode Constituent concentrations reported above a CL and confirmed in retest samples within the previous three years of monitoring were placed in "Tracking Mode" and are evaluated for temporal trends using Mann -Kendall trend analyses. The results of the trend analyses indicate that increasing trends were calculated for nitrate as nitrogen at well MW -10 and for chloroform at well MW -17 (Table 2-5). Of note, chloroform concentrations are well below the established state and federal maximum contaminant levels (MCLS) and the increasing trend is believed to be associated with landfill gas. Mann -Kendall trend analyses calculations are presented in Appendix G. As discussed previously Forward is in the process of increasing LFG extraction in the vicinity of this well. M:\ 2016.0007\FA 1Q16.docx 7