ARCHIVED REPORTS_2006_2 - Laserfiche WebLink

Home Browse Search

air conduit is present across the LCRS unit, and no excessive leachate is backed up in the drainage layer or sump of the LCRS unit. A summary of the test results is provided in Appendix A. Groundwater quality conditions beneath the Forward Unit during the fourth quarter 2006 monitoring period are generally similar to those observed in previous monitoring periods. One new historical intrawell maximum value was measured for dibromochloromethane in sample collected from groundwater monitoring well MW -1 during the fourth quarter 2006 monitoring period. However, this VOC is a suspected laboratory contaminant since similar concentrations were also measured in the QA/QC blank samples. Excluding suspected laboratory contaminants, estimated trace -level VOCs were measured in wells MW -1B, MW -14, and MW -17; and one VOC was measured above the PQL in well MW -14. CLs were exceeded for one or more monitoring parameters in samples from 13 wells. In accordance with the RPCMP, wells with exceedances of CLs will be resampled in February 2007 (during the first quarter 2007 sampling event), and a second independent sample will be collected in March 2007. The results of the two retests will be submitted to DTSC and RWQCB under separate cover. Historically, similar exceedances of CLs have been measured and verified in samples collected from DMP monitoring wells at the Forward Unit, followed by no release demonstrations (NRD), which have concluded that the CL exceedances are likely the result of naturally occurring conditions and therefore not indicative of a release from the Forward Landfill. Forward is currently installing additional landfill gas extraction wells and working to optimize the efficiency of the landfill gas extraction system. During the fourth quarter 2006 monitoring period, methane was measured at concentrations less than five percent in perimeter soil -pore gas probes, suggesting that the landfill gas extraction system is effectively reducing methane concentrations along the perimeter of the Forward Landfill. The results of the annual leachate sample indicates that of the constituents detected, only sulfide and 3-&-4-Methylphenol were potential new constituents of concern (CDCs). Verification samples will be collected from the Forward leachate sample point in February 2007 and reported with the first quarter 2007 monitoring report. 3.0 AUSTIN UNIT 3.1.1 Sampling and Laboratory Analyses The Austin Unit's DMP and CAP groundwater monitoring wells and surface water monitoring stations were sampled by ATC on November 28, 2006. Prior to collection of samples, depth -to -water measurements were recorded in the groundwater monitoring wells on November 27, 2006 D:X2003_021TorwardAustin_f06.dod 8 Geologic Associates