EPA Signs Off On Standards To Reduce Phosphorus Pollution In The Wisconsin River Basin

Several Lakes See Site-Specific Criteria To Cut Phosphorus Levels

Efforts made by the Wisconsin DNR to improve water quality throughout the Wisconsin River basin continue to move forward with the Environmental Protection Agency’s (EPA) approval of site-specific phosphorus criteria for Petenwell Lake, Castle Rock Lake and Lake Wisconsin.

The Total Maximum Daily Load (TMDL) for the Wisconsin River Basin, in which the three water bodies are located, requires substantial reductions in phosphorus. While phosphorus in all three lakes needs to be reduced, the statewide criteria were not appropriate for these water bodies.  The three lakes have experienced significant problems with algal blooms in the past. Phosphorus runoff from farms and urban areas has contributed to excessive blooms, which can sometimes produce toxins that make animals and people sick.

When the EPA approved the Wisconsin River Basin in 2019, they approved allocations based both on the statewide phosphorus criteria applicable at the time and the newly approved site-specific criteria. The allocations based on site-specific criteria are presented in Appendix K of the TMDL and will be used for future wastewater permitting decisions and as the basis for locally led nonpoint reduction plans.

More than 100 municipal and industrial facilities will be impacted by the new criteria under wastewater permits. The DNR said last fall that many are already or will soon be meeting limits.

For questions regarding the Wisconsin River Basin TMDL or the site-specific criteria, contact Pat Oldenburg, DNR Wisconsin River TMDL Project Coordinator, at patrick.oldenburg@wisconsin.gov or (715) 492-0589 or visit