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DNR considers changing phosphorus standards for 3 lakes

Associated Press

MADISON, Wis. (AP) — State environmental officials are considering changes to phosphorus regulations on three south-central Wisconsin lakes, a change that could cost wastewater treatment plants across the upper Wisconsin River basin millions of dollars in the coming decades.

The Department of Natural Resources is proposing loosening phosphorus restrictions on Petenwell and Castle Rock lakes in Adams, Juneau and Wood counties while tightening the standards on Lake Wisconsin in Columbia County. The agency’s board is scheduled to vote Wednesday on a scope statement outlining the plan.

An approval would give the department permission to begin working on regulatory language. The changes, though, would still need approval from the U.S. Environmental Protection Agency before they could take effect.

Scientists believe phosphorus runoff contributes to algae blooms that can sicken people and kill animals. Phosphorus can enter lakes and rivers through runoff from farms and lawns as well as industrial waste and sewage. Petenwell and Castle Rock lakes and Lake Wisconsin all are on the DNR’s 2018 list of impaired waters largely because of phosphorus pollution.

DNR staff wrote in May in a memo to board members that statewide phosphorus standards are more restrictive than they need be to preserve Petenwell and Castle Rock lakes for recreational uses but too lax to protect Lake Wisconsin.

The department’s plan calls for raising the phosphorus limits on Petenwell Lake from 40 micrograms a liter to 53 micrograms a liter and raising the phosphorus limits on Castle Rock Lake from 40 micrograms a liter to 55 micrograms a liter. The memo said the higher phosphorus concentration typically found in those two lakes produces less algae than in other Wisconsin lakes.

The limit on Lake Wisconsin, meanwhile, would drop from 100 micrograms a liter to 47 micrograms a liter. The lake is essentially a wide spot in the Wisconsin River and doesn’t retain phosphorus for long, the memo said. Even so, the area responds to phosphorus loading like a lake.

The memo notes that the changes would affect most of the Wisconsin River basin north of Lake Wisconsin, a 9,000 square-mile swath of the state that includes 21 counties, 85 municipalities and nearly 110 individually permitted wastewater plants.

Most of those plants are already installing equipment capable of holding phosphorus levels below the limits. Even so, 36 treatment plants— 29 municipal plants and seven industrial plants — are likely to take a hit. Two dozen plants can expect to save a total of $180 million over the next 20 years. The remaining 12 will most likely spend about $16.5 million to come into compliance over the course of the next two decades, the memo estimated.

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