ARCHIVED REPORTS_2001_1 - Laserfiche WebLink

Home Browse Search

VOC Detections above PQLs Lysimeter Samples 1999 and 2000 Quarterly Monitoring Events Lysimeter Analyte 1999 Detection 2000 Detection ARAR * (µg/l) No. (µg/1) 4tg/1) LY-117 chloroethane 0.74 ND NA LY-1F chloromethane 0.70 ND NA ' ND—Not Detected NA—Not Appropriate In addition to the VOCs identified above, 7 other VOCs were detected at trace concentrations (between the MDL and the PQL) in lysimeter samples during 1999 and 2000. The trace level detected VOCs include: • 1,1,2-trichloro-1,2,2-trifluoroethane • dichlorodifluoromethane • benzene ' • ethylbenzene • cis-1,2-DCE • toluene • xylene As shown on the time-series plots provided in Appendix A, VOCs have historically been ' detected only sporadically and at low concentrations in lysimeter samples. The most commonly detected analytes in lysimeter samples include: benzene, ethylbenzene, cis- 1,2-DCE, dichlorodifluoromethane, and trichlorofluoromethane. ' 2.3 LANDFILL GAS Landfill gas migration monitoring at the perimeter monitoring probes does not typically indicate the presence of elevated methane concentrations. However, considering that these probes were constructed only to a depth of approximately 5 feet, subsurface ' migration of gases within relatively permeable soil horizons may not be detected by the probes. 3.0 SOURCE OF VOCs In addition to methane, landfill gas often contains minor volumes of organic constituents. Landfill gas may impact groundwater directly by mixing with it, or hot landfill gases move to cooler soil zones outside refuse where the gases may condense. The newly condensed landfill liquid may then migrate vertically to impact groundwater. Taken together, several factors strongly indicate that landfill gas production from WMU-B is the source for VOCs in groundwater in wells adjacent to the FSL. These factors include: • WMU-B is the only unlined landfill cell, and VOC detections are concentrated near the unit. 6 ' GeoLogic Associates