The Shiawassee River Superfund site covers the former Cast Forge Company property and about eight miles of the Shiawassee River in Howell, Michigan. Aluminum manufacturing at the facility discharged wastewater laced with polychlorinated biphenyls (PCBs) into the river and an on-site lagoon from 1969 until 1977. PCBs turned up in soils, monitoring wells, and river sediments as far as fourteen miles downstream. The EPA added the site to its National Priorities List (NPL) in September 1983.
Cleanup has been organized into separate operable units (OUs), each targeting a specific problem. For soil and sediment (OU 01), the EPA selected a remedy in 2001 that included excavation, offsite disposal, monitoring, and institutional controls. Workers removed PCB-contaminated soil from the facility and floodplain and dredged contaminated sediment from the river between November 2004 and August 2005. Operation and maintenance activities for this area began in 2013 and continue today. Post-remediation sampling checks whether river sediment meets the cleanup goal of less than 5 parts per million PCBs in the first mile downstream. A second operable unit (OU 02) was created in 2023 after volatile organic compounds (VOCs) were found in soil, groundwater, and indoor air at the property. A combined remedial investigation and feasibility study for OU 02 is expected to start between June and August 2026.
The site has not yet been deleted from the NPL. EPA assessments indicate human exposure is not currently under control. Physical construction of the initial cleanup is complete, but cleanup goals have not been fully achieved across the entire site, and groundwater contamination movement has not been confirmed as stable. A fish consumption advisory remains in place because PCBs have been detected in fish. Zoning restrictions limit land use to commercial purposes and prevent residential development. As of December 2024, five businesses operating on the site employed 26 people and generated roughly $2.2 million in annual sales revenue. The most recent five-year review was completed on July 19, 2024.
Community members who want to review site records can visit the Howell Carnegie District Library at 314 W. Grand River in Howell, Michigan. Questions can be directed to the Community Involvement Coordinator or Remedial Project Manager assigned to the site.
