The MPCA’s Closed Landfill program oversees more than 110 old landfills in Minnesota. Freeway Landfill in Burnsville is currently their highest priority for addressing risk. One of Minnesota’s first landfills permitted by the MPCA, Freeway Landfill was constructed in the early 1970s before liners were required to be installed beneath municipal waste landfills. The site involves a unique setting with relatively shallow bedrock and is located adjacent to the Minnesota River and a deep rock-quarrying operation where significant dewatering has been ongoing for decades. The existing groundwater conditions have been heavily influenced by the long-term dewatering, leaving the water table artificially depressed in the bedrock below the landfill waste. Concerns have emerged that groundwater will rise into the waste in the future when quarry operations end, posing new risks to the river, nearby public water-supply wells, and the future lake that will form at the quarry pit. Another concern is the presence of emerging contaminants of concern, including 1,4-dioxane and per- and polyfluoroalkyl substances (PFAS), which are receiving further regulatory scrutiny at old landfill sites.
Barr assisted the MPCA with site investigation, alternative assessment, and preliminary design, including developing several preliminary layouts and budget estimates for landfill closure. We are also assisting with a complex stakeholder group (include multiple levels of regulatory input), and we conducted an analysis of potentially relevant federal, state, and local regulations and technical requirements for the alternatives under consideration. Barr’s supporting efforts included evaluating costs, benefits, and regulatory compliance for a range of liner designs for the on-site alternative and completing field studies (including wetland delineations, tree and raptor surveys, and floodway evaluation) in support of environmental review and permitting for the project. Barr is completing a detailed design for MCPA’s selected approach and is assisting with community engagement and environmental permitting in support of project construction.