Groundwater Monitoring Strategies in a Complex Hydrogeologic System for a Closed Solid Waste Landfill, 1998 Environmental Conference Proceedings

Dale H. Rezabek, P.G., C.P.G.

Steven L. Streblow, P.E., C.H.M.M.

RMT, Inc.

Anita Doepke

Menominee Paper Company, Inc.

Some important lessons were learned from a landfill closure in a complex hydrogeologic setting. The site was an unlined pulp and paper by-product solid waste and fly ash landfill. The landfill, which was located on thin glacial till over limestone bedrock, was adjacent to a large wetland, with groundwater discharging to surface water in the wetland. Historical data showed impacts to groundwater from the unlined facility. The objective was to close the site with a geomembrane cover, and allow for natural processes to improve groundwater quality as it discharged into the wetland. The groundwater flow system was complicated, though, by the interaction of groundwater in glacial till, bedrock, and the wetland. Originally, the areas of groundwater impact and migration were difficult to explain. Several phases of investigation helped to define the hydrogeologic system and develop a conceptual model for the flow system to explain the distribution of the groundwater geochemistry. In addition, the impact of leachate on groundwater was differentiated from the natural occurrence of the constituents of concern in the groundwater system. A closure groundwater monitoring system was then designed for the site and the groundwater/surface water interface in the wetland. The site eventually had A remedial action plan was eventually approved for the site by the state to

assess and monitor the wetland or implement active remediation if water standards were exceeded, ensuring that the site was protective of the environment.