SU0007861 - Laserfiche WebLink

Home Browse Search

Impact Report Pa Draft Environmental Imp e IV.F-12 p g Forward Inc. Landfill Expansion Groundwater quality at the Forward Landfill is summarized in the quarterly and annual monitoring per the RWQCB Cleanup and Abatement Order R5-2008-0714. Reports are submitted to the RWQCB and DTSC and can be viewed by the public on the California ' Geotracker system (http://geotracker.swrcb.ca.gov/). The current groundwater contamination from the Forward operations exhibits a large but diffuse plume of VOCs, specifically the key compounds of concern tetrachloroethene (PCE);trichloroethene (TCE); cis-1,2-dichloroethene (DCE);and vinyl chloride (VC). Within the plume, PCE and TCE have been the primary chemicals with concentrations above regulatory standards since monitoring was initiated in 1977 at the Forward landfill unit. This plume is shown on Figure IV.F-3. ! .�. The groundwater-monitoring system at the Forward Landfill is designed to detect the presence of contaminants in groundwater by analyzing groundwater chemistry at point-of-compliance wells. The monitoring system currently consists of 36 groundwater-monitoring wells, which G meet the requirements of the landfill's Detection Monitoring (DMP) for groundwater monitoring and the Corrective Action Program (CAP)for groundwater contamination. Currently VOC's are detected at low concentrations in selected well monitoring the Forward and Austin landfill units (disused in detail in water quality section below). Until their abandonment in 1993, VOCs were most commonly detected in monitoring wells MW-5A and MW-5B, near the southern border of WMU B (Figure IV.F-1). Since then, VOCs have been most commonly detected in the northeast corner of the Forward Landfill,in the main entrance facilities area. i In September 2000, the RWQCB requested that Forward assess the source and potential impacts of low-level VOC concentrations in the groundwater adjacent to the landfill. The assessment was performed by GeoLogic Associates (GLA)and summarized in the Low-Level VOC Detections in Monitoring Wells letter report (February 2001). The report found that, excluding acetone and methyl chloride (common laboratory contaminants), VOCs were detected in samples from 8 monitoring wells during 1999 and 2000. VOCs were most commonly detected at trace levels and in samples obtained from wells MW-13, MW-14, and MW-21, in the Fn northeastern corner of the existing Forward Landfill. The most frequently detected VOCs in groundwater include:benzene, cis-1,2-dichloroethene,tetrachloroethene, toluene, 1,1- dichloroethane, and 1,1,1-trichloroethane. The concentrations at which these analytes were �r detected did not exceed state or federal drinking water standards. Based on a review of the existing data, the GLA report finds that several combined factors indicate that landfill gas production in WMU B is a significant contributing source of VOCs in the groundwater at the existing Forward Landfill. These factors include: the locus of VOC detections near unlined landfill cell WMU B, the erratic pattern of low VOC detections,the relative long list of VOCs that are detected, the detection of VOCs in both upgradient and f downgradient monitoring wells, and the consistency of inorganic water quality in both upgradient and downgradient wells near the site. GLA concluded that the potential impacts associated with the VOCs in the groundwater appear to be small because the concentrations of FVOCs are well below drinking water standards and the absence of VOCs at offsite monitoring locations indicate that VOCs degrade or disperse within a relatively short distance of the landfill boundary. At the Austin Road Landfill unit where a Solid Waste Quality Assessment Test in 1989 found a significant groundwater quality impacts as a result form the unlined nature of the(Class III) landfill, the subsequent remediation at the north side of the landfill has resulted in insignificant increases in the VOC contamination, although concentrations are still above regulatory limits. This has been documented in the various monitoring reports and additional corrective action studies completed up through 2008.