Dam failure threatens endangered mussels

MANAWA - The failure of the Manawa Dam on the Little Wolf River in 2024 damaged the habitat for a federally listed endangered species, according to Mayor Mike Frazier.

Frazier wrote in a letter to the U.S. Army Corps of Engineers last month that the snuffbox mussel has significant populations in the Little Wolf River.

Following the dam failure, sandbars formed immediately downstream, burying portions of the riverbed by more than two feet and altering habitat conditions relied on by the species, he said.

Snuffbox mussels are an endangered species declining throughout their range due to habitat modification and destruction, sedimentation and pollution, according to the U.S. Fish and Wildlife Service (USFWS). In Dec. 2024, USFWS proposed designating 4,000 miles of rivers and streams in 17 states including Wisconsin as “critical habitat” for snuffbox and three other endangered freshwater mussel species.

The dam failure occurred July 5, 2024, after Manawa received 5.7 inches of rain in about four hours, with most of the precipitation falling within a single hour. The storm caused widespread flooding and created an emergency at the 130-year-old dam.

Frazier said debris from the storm clogged the gates and the dam was overtopped. An earthen berm then failed, leading to the breach. The dam failure caused the 180-acre Manawa Millpond to drain completely.

The City of Manawa and Town of Little Wolf have since begun moving forward with plans to rebuild the dam without reinstating its hydroelectric component, which is estimated to cost about $8.4 million. The city and town are seeking outside state and federal funding assistance to help cover the reconstruction cost.

In a letter to Congressman Tony Wied, Frazier said the loss of the mill pond has affected the community’s economy, recreation and heritage.

“The restoration of the mill pond is vital,” he wrote.

Frazier said a modern dam designed with engineering consultants and the Wisconsin Department of Natural Resources is the only viable way to safely manage the Little Wolf River and preserve the reservoir’s ecosystem.