The Madison Metropolitan Sewerage District Lagoons is a 183-acre wastewater treatment facility near Madison, Wisconsin that has operated since 1933. A dike failure in April 1970 released about 85 million gallons of lagoon contents into a nearby ditch. Testing in 1982 found high levels of polychlorinated biphenyls, or PCBs, in sludge, which led EPA to add the site to the National Priorities List in 1990.
EPA identified 49 contaminants of concern at the site. These were found in sludge, soil, and liquid waste. The list includes heavy metals such as arsenic, cadmium, chromium, lead, and mercury, organic chemicals like benzene, toluene, and xylene, pesticide residues including DDT compounds and PCBs, and metals such as copper, nickel, selenium, and zinc. EPA determined all of these substances require cleanup based on the amounts present and their potential effects on human health and the environment.
The Sewerage District entered into a cleanup agreement with EPA in 1992. A final remedy was selected in March 1997. It focused on reducing exposure to PCB-contaminated sludge through dike construction to isolate contamination, soil cover with seeding, and long-term monitoring. Sludge with low PCB levels was used in an agricultural program through 2000. Construction of the remedy ran from January 1998 through September 2001. In June 2018, EPA and the Wisconsin Department of Natural Resources updated the site's institutional controls through an Explanation of Significant Differences to better limit site use and access.
Human exposure across the entire site is currently under control. There are no unacceptable exposure pathways, all required land-use restrictions are in place, and construction is finished. The site achieved sitewide ready for anticipated reuse status in September 2010. EPA conducts five-year reviews to confirm protections continue to work. The most recent review was completed in March 2023. The next review is estimated to occur between March and May 2028. The site has not yet been deleted from the National Priorities List.
Community members with questions can contact EPA's Community Involvement Coordinator or the Remedial Project Manager. EPA's five-year review process is one way the public can track whether cleanup protections remain effective over time.
