Delavan Municipal Well #4 sits near South Wright Street in Delavan, Wisconsin. The well was closed in 1982 after volatile organic compounds, known as VOCs, contaminated the aquifer it drew from. EPA added the site to the National Priorities List in 1984. A remedial investigation began in 1990, and EPA selected a final remedy in September 2000. Construction of that remedy was also completed in September 2000.
EPA identified eleven contaminants of concern at the site. They include 1,1,1-trichloroethane, 1,1,2-trichloroethane, chloroethene (vinyl chloride), tetrachloroethene, trichloroethene, trichloroethane (mixed isomers), and related chlorinated solvents. Tetrachloroethene, trichloroethene, and trichloroethane were found in both groundwater and soil. The remaining contaminants were detected in groundwater only. EPA selected these substances as concerns because they pose an unacceptable risk to human health or the environment based on the amounts present and their potential health effects.
The cleanup combines actions by potentially responsible parties and federal and state agencies, with the state taking the enforcement lead. The remedy includes an extraction well, a groundwater aeration system, soil vapor extraction, thermal treatment, and air stripping. Since 1993, treated water from Well #4 has been processed through a VOC-stripping tower and blended with water from two other wells before reaching customers. Contaminant levels in that water stay consistently below health-risk levels. VOC emissions from the aeration system are monitored under an air permit and do not exceed permitted levels. An Explanation of Significant Differences issued in June 2018 updated cleanup performance standards and added institutional controls.
Human exposure is under control. EPA assessments show no unacceptable human exposure pathways exist at the site. Groundwater migration is also stabilized, with no unacceptable discharge to surface water. The site achieved sitewide readiness for anticipated reuse in July 2018. One on-site business currently employs 345 people and generates about $142 million in annual sales, as of December 2024. EPA will continue monitoring to confirm that contaminated groundwater stays within the original area of contamination.
Community members can follow the site's progress through EPA's regular five-year reviews, the most recent of which was completed on August 6, 2025. These reviews confirm that the cleanup continues to protect people and the environment. For questions, residents can contact Community Involvement Coordinator Meshach Padilla or Remedial Project Manager Kelly Poulos using the contact information below.
