Phosphorus standards recently adopted in Wisconsin may result in significantly more restrictive and expensive compliance requirements for Minnesota municipalities and agricultural interests. The standards divide Wisconsin lakes and rivers into twelve categories and apply phosphorus standards ranging from 100 ug/L for certain listed rivers, down to 5 ug/L for Lake Superior open and nearshore waters. The allowable loading is calculated based on a two-year low-flow regime. Significantly, the standards apply regardless of the actual impact on algal growth.

These standards could create problems for Minnesota because the Mississippi River serves as the border between the two states and, under federal law, the border state must achieve the stricter standard. As approximately 70 percent of the state drains into the Mississippi River, wastewater facilities throughout the state could be forced to undergo expensive retrofits.

Flaherty & Hood is working with affected stakeholders on these standards and intends to meet with EPA administrators on addressing this interstate issue.