Landfill Gas As Source of VOCs in Ground Water

During 1993 and 1994, Waste Management, Inc. and RUST Environment & Infrastructure conducted a complex site investigation at a municipal waste landfill to investigate whether landfill gas and/or leachate was the source of volatile organic chemicals (VOCs) detected in certain ground-water monitoring wells. The study was conducted in two phases. During the first phase, an investigation plan was prepared to identify VOC transport mechanisms and investigational procedures. After approval of the plan by the state regulatory agency, actual investigation and data evaluation were performed. Potential VOC transport mechanisms, including those associated with landfill gas migration, were evaluated as part of the study. Overall, investigation findings indicate that relatively broad exchanges of VOCs from landfill gas in the vadose zone to ground water exist. A much stronger correlation exists between the types of VOCs present in landfill gas and ground water than between the types of VOCs present in leachate and ground water. Since report findings indicate that landfill gas migration is the most likely dominant source of VOCs in ground water, follow-up action at the site will include accelerating the schedule for installing the remaining 42 gas extraction wells. Also, out-of-refuse gas collection trenches and/or gas extraction wells will be installed in the eastern portion of the landfill, where VOCs are present in the highest concentrations.