DNR Evaluating Plan to Shut Down Wauleco Treatment System
- Dioxin, Pentachlorophenol, SNE / Wauleco / Sentry Insurance, Wisconsin River
- November 9, 2026
Despite levels of pentachlorophenol in some Wausau groundwater monitoring wells that are thousands of times higher than the state enforcement standard, a Responsible Party (RP) for the Wauleco SNE Corp site, Rosecrans Properties LLC, has submitted a pilot test plan to shut down the pump-and-treat system. For perspective, wells like W40R had levels of penta in the groundwater as high as 4,200 ug/l, based on the latest winter groundwater sampling. The Wisconsin limit for penta in groundwater is 1 ug/l.
The September 2026 plan, “Pump-and-Treat System Shutdown Pilot Test Plan,” can be downloaded and reviewed from the DNR’s BRRTS website. The RP’s consultant states in the plan, “Due to significant mass removal during more than 35 years of operation, the P&T system has entered a phase of diminished effectiveness.”
In late October, Citizens for a Clean Wausau (CCW) submitted comments to the DNR about the plan. The comments emphasized that shutting down the treatment system would be concerningly premature because the Responsible Party has yet to provide definitive scientific proof that the following things are happening, even though the DNR has repeatedly characterized them as prerequisites:
- Biodegradation is the primary “natural attenuation” mechanism for the groundwater plume, including its central portion — not other possibilities like dilution or displacement from things like water main leaks, aggressive dewatering in nearby areas, and construction, some of which impacted utility corridors.
- This “natural attenuation” will effectively restore the environment by bringing groundwater contamination levels under the Wisconsin enforcement standard in a reasonable amount of time.
- The site’s groundwater pollution does not currently pose a risk to any receptors and would not pose a risk to them if the treatment system is shut down.
As the CCW comments mention, over 40 years after remedial efforts began, around 5,000 pounds of PCP reportedly still remain concentrated in an area smaller than one acre.
Additionally, a 2022 PowerPoint of the Wauleco site’s consultant showed that if state regulators allow “natural attenuation” of the contaminated groundwater, it could take up to 95 years of “cleanup time” in certain areas. In its comments to the DNR, CCW said the timeframe and extreme restoration estimate conflict with most credible notions of a “reasonable period of time,” which is another key requirement in Wisconsin for natural attenuation to be allowed.
The Responsible Party for the site and its consultant also recently conducted a study of the Wisconsin River, to which the contaminated groundwater plume has been discharging for decades, involving a highly limited number of sediment and surface water samples. The study and report seemed to potentially omit numerous important elements — based on the years of public records and data on the Wauleco site’s DNR page — such as failing to test near wetland areas south of the Thomas Street bridge, where pentachlorophenol had been identified in the 1980s. Penta from the Wauleco plant has been discharging from the wastewater plant’s outfall for years, into the Wisconsin River near the wetlands.
