September 4, 2025
Toxic Coal Ash in Wisconsin: Addressing Coal Plants’ Hazardous Legacy
For many decades, utilities dumped billions of tons of coal ash — the toxic substance left after burning coal — in unlined ponds, landfills, and mines where the toxic pollution leaks into water and soil.
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Across the U.S., immense coal ash dumps are leaking hazardous chemicals including arsenic, chromium, lead, lithium, radium, and other heavy metals, which have been linked to numerous types of cancer, heart and thyroid disease, respiratory illness, reproductive failure, and neurological harm. In addition to those well-known health threats, in 2023, the Environmental Protection Agency acknowledged that coal ash contains levels of arsenic and radiation that pose cancer risks.
Coal ash remains one of our nation’s largest toxic industrial waste streams. U.S. coal plants continue to produce approximately 70 million tons every year. Coal ash is disproportionately located in low-income communities and communities of color.
Industry’s own data indicate that across the country almost all coal plants are polluting water above federal safe drinking water standards.
Despite regulations established a decade ago, the coal industry has failed to comply with federal safeguards and uses deceptive tactics to avoid cleaning up its coal ash.
Because of industry’s widespread violations of coal ash regulations, in 2023, the EPA ramped up enforcement after designating coal ash a national enforcement priority. The EPA reports that many plants are illegally closing coal ash ponds with toxic ash sitting in groundwater, threatening drinking water and the health of nearby residents.
The longer industry delays, the more toxic waste enters our water, and the more difficult cleanup becomes. But the coal industry is asking Trump’s EPA to let them off the hook.
Action Needed
Federal coal ash protections established in 2015 and 2024 require monitoring, closure, and cleanup of the more than 1,000 coal ash dumps across the country. Cleaning up coal ash now will not only prevent another billion-dollar catastrophic failure, it will preserve drinking water; protect rivers, streams, and lakes; and allow safe redevelopment of power plant sites.
The magnitude of harm from recklessly dumped toxic coal ash requires decisive action from federal and state regulators:
- Power companies must be required to comply with the law and immediately clean up their pollution, including removing any coal ash in contact with groundwater.
- When power companies retire coal plants, they must clean up their toxic mess and leave communities with sites that benefit rather than harm their health, environment, and economy.
- EPA and states must prohibit the use of coal ash as a substitute for clean soil in construction (known as structural fill), especially in residential areas, and ensure cleanup of areas where ash was used as fill.
Click on plant locations on the map to see industry reports
Coal Ash in Wisconsin
| Alma | Dairyland Power Coop | 1 legacy pond(s), and 3 potential ash dump(s) | 1 legacy pond(s), and 3 potential ash dump(s) | No data yet | 2007 EPA report found evidence of Manganese and Sulfate contamination | WI-03 (Derrick Van Orden) |
| Bay Front | Northern States Power Co. - Minnesota | 2 likely inactive pond(s), and 2 potential ash dump(s) | 2 potential ash dump(s) | No data yet | No groundwater data reported | WI-07 (Tom Tiffany) |
| Columbia | Wisconsin Power & Light Co. | 2 pond(s), 3 landfill(s), and 3 potential ash dump(s) | 3 potential ash dump(s) | 1,791,255 | Arsenic (x2), Boron (x1), Molybdenum (x2) | WI-06 (Glenn Grothman) |
| Edgewater | Wisconsin Power & Light Co. | 4 pond(s), 1 landfill(s), and 3 potential ash dump(s) | 3 potential ash dump(s) | 613,800 | Arsenic (x2), Boron (x5), Cobalt (x1), Lithium (x1), Molybdenum (x55) | WI-06 (Glenn Grothman) |
| Genoa | Dairyland Power Coop | 2 likely inactive pond(s), and 2 potential ash dump(s) | 2 potential ash dump(s) | No data yet | No groundwater data reported | WI-03 (Derrick Van Orden) |
| John P Madgett | Dairyland Power Coop | 1 landfill(s), and 2 potential ash dump(s) | 2 potential ash dump(s) | 1,253,000 | Antimony at unsafe levels. See Ashtracker. | WI-03 (Derrick Van Orden) |
| Nelson Dewey | Wisconsin Power & Light Co. | 2 pond(s), and 1 potential ash dump(s) | 1 potential ash dump(s) | 75,000 | Boron (x2), Molybdenum (x1), Thallium (x1) | WI-03 (Derrick Van Orden) |
| Pleasant Prairie | We Energies | 1 landfill(s) | None estimated | 110,210 | Molybdenum (x4) | WI-01 (Bryan Steil) |
| Port Washington Generating Station | Wisconsin Electric Power Co. | 1 potential ash dump(s) | 1 potential ash dump(s) | No data yet | 2007 EPA report found evidence of Boron, Selenium, and Sulfate contamination | WI-06 (Glenn Grothman) |
| Pulliam | Wisconsin Public Service Corp. | 2 potential ash dump(s) | 2 potential ash dump(s) | No data yet | 2007 EPA report found evidence of Sulfate, Manganese, Iron, Boron, Zinc, Aluminum, Chloride, Total Dissolved Solids, and pH contamination | WI-08 (Tony Wied) |
| Rock River | Alliant Energy, Wisconsin Power and Light Co. | 1 legacy pond(s) | 1 legacy pond(s) | 2,000 | 2007 EPA report found evidence of Arsenic, Mercury, Selenium, Iron, Sulfate, and Total Dissolved Solids contamination | WI-02 (Mark Pocan) |
| South Oak Creek | We Energies | 1 landfill(s), and 2 potential ash dump(s) | 2 potential ash dump(s) | 1,660,000 | Molybdenum (x1) | WI-01 (Bryan Steil) |
| Valley | Wisconsin Electric Power Co. | 4 potential ash dump(s) | 4 potential ash dump(s) | No data yet | 2014 EPA report found evidence of Arsenic, Boron, Molybdenum, Manganese, Iron, Chloride, Selenium, Total Dissolved Solids, Sulfate contamination | WI-04 (Gwen Moore) |
| Weston | Wisconsin Public Service Corp. | 4 pond(s), 1 landfill(s), and 5 potential ash dump(s) | 5 potential ash dump(s) | 464,400 | Cobalt (x2) | WI-07 (Tom Tiffany) |
* Total volume of coal ash reported as of 2021 for ponds and landfills regulated under the 2015 Coal Ash Rule, and as of 2024 for legacy ponds at power plants that retired before October 2015. This volume does not include any of the potential ash dumps that will begin reporting in 2026.
** Parentheticals indicate magnitude of exceedance above federal health-based guidelines for drinking water based on industry data and analysis described in the report, Poisonous Coverup. See summaries of EPA reports.
Massive quantities of toxic coal ash are stored at 14 coal-fired power plant sites in Wisconsin.
All but one of these sites include older coal ash dumps that industry is only now beginning to quantify and monitor.
Power plant owners must report on an estimated 32 older coal ash dumps in Wisconsin for the first time, under the safeguards established by the 2024 Legacy Coal Ash Rule. Those dump sites are in addition to 12 ponds (eight of which have no protective liner to prevent leaks) and eight landfills that are covered by the 2015 Rule. Those 20 ash dumps contain nearly six million cubic yards of toxic coal ash. That’s equivalent to a football field piled more than half-a-mile high with coal ash.
At all but one of the Wisconsin plants that have conducted groundwater monitoring, industry data reveal groundwater contamination above federal safe drinking water standards. At the remaining plant site, groundwater contains unsafe levels of coal ash pollutants, but the specific source cannot yet be determined by the existing monitoring system.
For More Information
Christine Santillana, Senior Legislative Counsel, Earthjustice, csantillana@earthjustice.org
Lisa Evans, Senior Counsel, Earthjustice, levans@earthjustice.org.
About the Map
- EPA’s first coal ash regulations, issued in 2015, covered only some coal ash dumps, exempting older ponds and landfills at current and former coal plant sites.
- In 2024, EPA extended federal monitoring and cleanup requirements to hundreds of previously excluded older coal ash landfills and ponds leaking toxic pollution into groundwater and surface water. Industry is now required to monitor those older dump sites, filing initial reports on so-called ‘legacy’ ponds at former coal plants in 2024.
- In 2026, industry will be required to report on additional dump sites at operating power plants that did not receive ash after Oct. 19, 2015. Groundwater monitoring requirements are not yet in effect for these newly regulated dumps, so the table below may lack specific information about the number of units and the extent of contamination at a particular site.
More on Coal Ash in Wisconsin
Coal Ash in States, Territories, Regions
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