News Release

Zebra mussels confirmed in Rouchleau Mine Pit near Virginia

August 9, 2019


Water pumping temporarily on hold

The Minnesota Department of Natural Resources has confirmed zebra mussels in the Rouchleau Mine Pit near Virginia in St. Louis County. 

The historic Rouchleau Pit is near an active taconite mine and was being dewatered to facilitate future mining. Environmental staff from the mining company discovered zebra mussels during a routine inspection of the dewatering operation. Lower water levels revealed widespread living and dead zebra mussels in the shallow water near the pumping station in the pit.

The mining company stopped the pumping operation and took immediate steps to report the discovery. The DNR confirmed zebra mussels on rocks and debris in the mine pit.

The water from the pit was being pumped into a drainage ditch that flows into a shallow wetland known as Ramshaw Lake, which eventually flows into Long Lake Creek and the St. Louis River. Those nearby waters are not known to have zebra mussels. The St. Louis River eventually flows into Lake Superior, where zebra mussels were first confirmed in Minnesota in 1989.

The DNR will review all existing permits to take water from the Rouchleau Pit and connected waters and will meet with permit holders to determine the most appropriate of several potential measures to prevent the spread of zebra mussels. The DNR will conduct additional monitoring for zebra mussels in downstream and nearby waters.

The Rouchleau Pit is part of a larger pit complex known as the Missabe Mountain Pit Complex. The Missabe Mountain/Moose-Shaw/Rouchleau pits make up the Missabe Mountain Pit Complex. The pit complex is currently one contiguous body of water.

The DNR reminds boaters and anglers to follow Minnesota laws to prevent the spread of aquatic invasive species:

  • Clean watercraft and trailers of aquatic plants and prohibited invasive species.
  • Drain all water by removing drain plugs and keeping them out during transport.
  • Dispose of unwanted bait in the trash.

Some invasive species are small and difficult to see at the access. To remove or kill them, take one or more of the following precautions before moving to another waterbody:

  • Spray with high-pressure water.
  • Rinse with very hot water (120 degrees for at least two minutes or 140 degrees for at least 10 seconds).
  • Dry for at least five days.

Zebra mussels can compete with native species for food and habitat, cut the feet of swimmers, reduce the performance of boat motors, and cause expensive damage to water intake pipes.

People should contact an area DNR aquatic invasive species specialist if they think they have found zebra mussels or any other invasive species that has not already been confirmed in a lake.

More information is available at mndnr.gov/ais.