Efforts made by the Wisconsin Department of Natural Resources 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.
A TMDL is the calculation of the maximum amount of a pollutant allowed to enter a waterbody so that the waterbody will meet and continue to meet water quality standards for that particular pollutant. A TMDL determines a pollutant reduction target and allocates load reductions necessary to the source(s) of the pollutant. Additional information on TMDLs can be found on the EPA website.
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.
A copy of the EPA approved TMDL plan and associated appendices can be found here. For questions regarding the Wisconsin River Basin TMDL or the site-specific criteria, contact Pat Oldenburg, DNR Wisconsin River TMDL Project Coordinator, at [email protected] or (715) 492-0589.