Alliant’s Columbia Energy Center near Portage had two times the safe level of arsenic and molybdenum and is the only site in Wisconsin considered to have “significant contamination.” According to the Wisconsin Department of Natural Resources, the ash pond there leaks about 433,000 gallons of water per day into the ground.

The DNR has proposed granting a five-year wastewater permit without imposing federal requirements that Alliant stop mixing coal ash with water by next year.

Alliant has said it will eliminate wet ash handling at Columbia by 2023. The company last year switched to dry ash handling at its Edgewater Generating Station in Sheboygan and plans to close the remaining ponds there by the end of 2020.

“All of our ponds meet safety requirements. We’re in compliance with the rules,” said Alliant spokesman Scott Reigstad. “The information we have now doesn’t indicate any concern for wells that supply drinking water.”

Dairyland Power Cooperative’s coal ash landfill in Alma is one of only 11 in the nation that showed no unsafe levels of pollutants in the groundwater.

Russ said landfills are generally less likely to leak than ponds and that the 32-acre Alma site is relatively small. The La Crosse-based utility declined to comment on the report.