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Zebra mussels in Canisteo Mine Pit interrupt plan to lower water levels

Both the temporary and permanent fixes could see changes to prevent the spread of the invasive species.

Small community near mine pit cloudy day
The community of Bovey sits next to the Canisteo Mine Pit seen Aug. 24. Officials are looking for a solution to rising levels that could cause water to overflow over the edge of the pit.
Clint Austin / File / Duluth News Tribune
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BOVEY — The discovery of an invasive species in a series of abandoned mine pits on the Iron Range has disrupted plans to alleviate rising waters in the pits.

The Minnesota Department of Natural Resources on Sept. 12 confirmed zebra mussels were in the Canisteo Mine Pit complex near Bovey, corroborating an angler's earlier finding.

Water levels in the Canisteo Mine Pit have been going up since the 1980s. They could soon rise over the lowest wall of the pit.

The zebra mussels, which can cause expensive damage to water intake pipes and can reduce or block water flow into intake pipes, were discovered just over two weeks before the state agency was scheduled to begin pumping water out of the pits to ensure water doesn't overwhelm drainage tile between the pit and low-lying Bovey homes or crest over the lowest edge of the pit. The pumps would also lower the water level enough to put a permanent fix in once enough funding is secured.

Canisteo Mine Pit.jpg
Gary Meader / Duluth News Tribune

But ensuring the invasive species doesn't spread to new waters puts into question both the temporary pump plan and permanent fix, which would use gravity to take water from the pit under County Highway 61 into a wetland complex where it will flow naturally through the West Hill and Lind pits and finally the Prairie River.

Now, the agency is looking to add filters to the pumps said Mike Liljegren, the Minnesota Department of Natural Resources division of land and minerals assistant director.

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"With the discovery of zebra mussels in the Canisteo, the DNR is working to secure a filtration system that would allow us to comply with invasive species requirements by filtering the water prior to transferring the water out of the pit," Liljegren said in an email to the News Tribune. "The system will need to be tested before becoming fully operational."

The Department of Iron Range Resources and Rehabilitation in August gave the DNR $710,000 to begin pumping water out of the pit in October, but that's been delayed because of the zebra mussel discovery. The DNR does not have an updated cost for the pumping project.

ZebraMusselsWeb.jpg
A cluster of zebra mussels sits on a navigation buoy that was pulled from Lake Superior.
File / Duluth News Tribune

Water containing zebra mussel larvae, called veligers, has generally been filtered and/or treated to eliminate veligers before it can be used for drinking water or discharged to prevent the spread of invasive species in downstream receiving waters.

But if water temperature falls, they still might be able to pump without filters, Liljegren said.

"Water temperature is key (sustained at 53 degrees) to when the reproductive stage ends and the veligers drop out of the water column. We will monitor temperature and test for veligers before we begin any winter pumping," Liljegren said. "This will ensure that we can pump while still complying with the invasive species requirements."

The permanent fix is a culvert on the west end of the mine pit, near Mt. Itasca Winter Sports Center, installed at 1,305 feet to keep water levels from going any higher than that.

Canisteo Mine Pit water levels.jpg
Gary Meader / Duluth News Tribune

But that could also see some changes.

"We are evaluating our permanent outlet design to incorporate filtration or a winter-only pumping scenario," Liljegren said.

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Since mining — and dewatering — in the pit stopped in the 1980s, the Canisteo complex has been filing with water, pushing nearby groundwater higher and higher.

If a mining company were to stop mining in a pit today, its permit to mine would require it to carry out a reclamation plan for the future of its site, including control of pit water levels. But those weren't in effect then, and no one was on the hook for controlling the water levels.

That meant the basements of nearby Bovey homes were regularly flooding, damaging foundations.

There was a slight reprieve in the 2010s when scram mining company Magnetation had its Plant 4 pump water out of the pit for use in its operations in 2012, lowering water levels by more than 20 feet. But it filed for bankruptcy in 2015 and pumping stopped in 2016. ERP Iron Ore took over and pumped water briefly in 2017 and 2018 but it went bankrupt, too.

In 2011, the DNR built a drain tile system under Bovey’s First Avenue to carry groundwater away from homes in the low-lying areas of town and divert it to Trout Creek and Trout Lake.

But the drain tile is designed to work with water levels up to 1,318 feet. Any higher than that — without pumping, the pit would exceed that level next year — and the drain tiles could be inundated with water and become ineffective.

And if water levels reach 1,324 feet, it will begin flowing over the lowest part of the pit’s rim.

Small community near mine pit cloudy day
If water levels were allowed to rise in the Canisteo Mine Pit, this is the point where the water would overflow.
Clint Austin / File / Duluth News Tribune

Jimmy Lovrien covers energy, mining and the 8th Congressional District for the Duluth News Tribune. He can be reached at jlovrien@duluthnews.com or 218-723-5332.
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