Penta Wood Products

Overview

Penta Wood Products is an inactive wood treatment facility in Daniels, Wisconsin, that operated from 1953 to 1992. EPA added it to the National Priorities List (NPL) in 1996. The NPL is the federal list of hazardous waste sites that qualify for long-term cleanup funding. The site has not yet been deleted from the NPL.

The facility contaminated soil, groundwater, surface water, and sediment by treating wood posts and telephone poles, dumping process wastes, and spilling chemicals. EPA has identified 28 contaminants of concern at the site. These include pentachlorophenol (PCP), a wood preservative, along with metals such as arsenic, copper, and zinc, and organic compounds like benzene, toluene, xylene, and naphthalene.

EPA selected a cleanup plan in September 1998 covering excavation, capping, chemical oxidation, solidification and stabilization, and incineration of some materials offsite. The plan also includes replacement water supplies, groundwater monitoring, and monitored natural attenuation. Construction of the initial cleanup was completed by September 2000. In 2017, elevated PCP levels and surface debris containing arsenic, PCP, and other contaminants were found in three areas. EPA and the Wisconsin Department of Natural Resources (WDNR) ran a four-year pilot study ending in 2019 to assess whether natural processes could address remaining underground contamination. Based on those findings, further site characterization work began in 2023. Using funding from the Bipartisan Infrastructure Law, wetland excavation and surface debris cover work commenced that year.

EPA cannot yet conclude that human exposure is under control, citing uncertainty about exposures. EPA also cannot confirm that contaminated groundwater migration is stabilized, due to insufficient data. The site is not yet ready for all anticipated uses. WDNR has overseen operation and maintenance since 2014 and continues sampling and monitoring. The most recent five-year review was completed in June 2025.

Community members with general questions can contact the EPA's Community Involvement Coordinator. Technical questions about cleanup work can go to the Remedial Project Manager. Public documents are available through EPA's site collections, which include key documents, web content, and an administrative records collection of 195 documents.