St. Cloud looks to restore old stormwater tunnel for bats

The entrance to an old storm sewer
A brick-and-mortar storm sewer built in the 1900s in St. Cloud will be restored to provide habitat for northern long-eared bats, as part of a project to stabilize a ravine and prevent stormwater runoff to the Mississippi River.
Courtesy of city of St. Cloud

A century-old brick stormwater tunnel in St. Cloud will be restored to provide critical habitat for bats facing population declines due to a deadly fungal disease.

The city received a $2.3 million hazard mitigation grant from the Federal Emergency Management Agency for the project. Its main goal is to stabilize a 40-foot-deep ravine that cuts through urban St. Cloud.

Excess stormwater from increasingly heavy rainfalls is wearing away at the ravine and carrying sediment to the Mississippi River, said Emma Larson, the city's assistant public utilities director.

"The erosion is just getting worse and worse,” Larson said. “If anybody's in the ravine, or the properties on either side, it's starting to become a safety concern."

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The project will build a new, rerouted storm sewer to replace the existing brick-and-mortar tunnel that was built in the 1920s. Previous studies by the Minnesota Department of Natural Resources and St. Cloud State University found northern long-eared bats using the tunnel for hibernation.

That species, like others in Minnesota, have faced precipitous population declines due to white-nose syndrome, a fungal disease that can be fatal.

However, in 2016, DNR researchers found evidence that the tunnel was flooding to the top, making it unsuitable for the hibernating mammals. The storm sewer project will allow the old tunnel to be restored as a home for bats.

The total project cost was estimated last year at $3.5 million. St. Cloud also received $825,000 for the project from the state’s Environment and Natural Resources Trust Fund, which receives proceeds from the state lottery.

Larson said design work on the project likely will begin this winter, with construction ideally starting next spring. No work can be done between October and April to avoid disturbing the bats, she said.