The Muskego Sanitary Landfill is a 60-acre site in Muskego, Wisconsin that operated as a landfill, animal-rendering plant, and gravel quarry during the 1950s and 1960s. It was added to the EPA's National Priorities List (NPL) in 1984. The NPL is the federal list of sites that warrant long-term cleanup oversight. The site has not yet been deleted from the NPL, so active EPA oversight continues.
Contamination at the site affects soil and groundwater. EPA has identified 40 chemicals of concern, including volatile organic compounds (VOCs) such as vinyl chloride, benzene, toluene, and trichloroethene, as well as heavy metals like arsenic, lead, cadmium, mercury, and chromium. Polychlorinated biphenyls (PCBs), phthalates, and phenol are also present. Most contaminants are addressed under the Source Control Operable Unit, while PCBs in groundwater fall under the Groundwater Operable Unit.
Cleanup is organized into three main areas. Source control work ran from October 1993 through July 1996 and included an engineered landfill cap, landfill gas collection and treatment, soil vapor extraction, and leachate control. Groundwater remediation began in September 1997. The original groundwater approach used a pump-and-treat system. A 2004 review found contamination moving off-site, prompting more investigation. By 2010, EPA modified the groundwater remedy to rely on monitored natural attenuation (MNA), which means letting natural processes break down contaminants while tracking their progress through monitoring wells. Eight additional monitoring wells have been installed since then, and a plan is in place to protect the city of Muskego's municipal well from contamination.
Currently, human exposure is under control and contaminated groundwater migration is stabilized, with no unacceptable discharge to surface water. Physical construction of the cleanup is complete across the entire site. The site was declared ready for anticipated reuse in September 2018 after required institutional controls, such as land-use restrictions, were put in place. EPA completed its sixth five-year review in June 2024 and confirmed that cleanup actions continue to protect human health and the environment in the short term. An evaluation of the MNA approach is ongoing.
Community members with questions can contact the EPA's Community Involvement Coordinator or Remedial Project Manager.
