Canisteo Mine Pit

Please stay off the ice at the Canisteo Mine Pit, Holman Lake, and the surrounding wetlands.

The Canisteo is undergoing pumping right now to lower its water level, and that is creating some serious ice safety issues.

The pumps are pushing water out of the Canisteo (and into the wetlands that lead into Holman Lake) at a maximum rate of 11,000 gallons a minute. This can cause gaps between the ice and the unfrozen water underneath — known as an "ice shelf" — and if you fall through it is nearly impossible to rescue yourself.

Watch this ice safety video to learn more about what is happening and why it is important to stay OFF the ice on the Canisteo, Holman Lake, and the nearby wetlands this winter.

Brief overview

The Canisteo Legacy Mine Pit (Canisteo) is a pit lake formed in a complex of numerous inactive iron ore mine pits in Itasca County, Minnesota. The Canisteo is located north of the cities of Coleraine, Bovey, and Taconite.

Traditional iron ore mining began in the Canisteo in 1907 and continued through 1980. Mineland Reclamation Rules for ferrous mining were adopted in 1980, requiring mining operations to plan for closure and reclamation. Between 1980 and 1986, mining in the Canisteo consisted exclusively of scram operations. Reclamation was only required for disturbances connected to scram mining operations and not water level management. Therefore, the Canisteo is considered a legacy mine pit and no company is responsible for managing water levels.

The DNR's role in managing water at a pre-1981 site like the Canisteo Legacy Mine Pit, similar to numerous other water challenges across the state, is to provide technical expertise for and regulatory oversight of any water appropriation or work in public waters in accordance with Minnesota Statute 103G.

As water levels rose within the Canisteo, the full extent of potential hydrologic impacts to surrounding communities was unknown. Recognizing the importance of a data record from which water level predictions can be made, the DNR began monitoring for pit water level and surrounding groundwater changes in 1990.

An engineered outlet structure is necessary to control the pit’s water levels in a way that doesn’t adversely affect surrounding communities. As of January 17, 2023, the Canisteo water level is within 13 feet of the natural overflow elevation. Without pumping, the DNR estimates water would rise at a slow rate, and the pit would naturally overtop by late 2023 or in 2024. If the pit water level were to reach the overtopping elevation, water runout would occur slowly with surface water flowing at the lowest elevations along the pit rim.

The DNR and Iron Range Resources & Rehabilitation have been and will continue working with local communities to identify a long-term solution and seek the legislative funding necessary for construction and operation of an engineered outflow.

 

Canisteo water level management

City of Bovey drain tile system

Map drain tile system in the city of Bovey

Click to enlarge

After iron ore mining and subsequent pit dewatering ended, the Canisteo began to fill with water from precipitation, surface water inflow, and groundwater inflow. The increasing pit water level resulted in concerns from nearby communities, including a rising water table within the city of Bovey. The DNR designed and conducted various studies to evaluate potential impacts from the rising pit water level.

The effects from the already high water table in city of Bovey were worsened by the rising water level in the Canisteo. Groundwater flowed from the pit lake through subsurface materials to the south toward the city. In 2011, the DNR designed and constructed a drain tile system along 1st street. The drain tile system diverts groundwater away from residential structures located within the city.

In 2012, the DNR issued a water appropriation permit to Magnetation LLC, a scram mining operation, authorizing the pumping of water from the Canisteo for mining operations. This pumping resulted in a decrease in the water level until Magnetation LLC filed for bankruptcy in 2015. Pumping ceased in 2016, resulting in a rising pit water level.

ERP Iron Ore LLC acquired Magnetation LLC assets and resumed intermittent pumping in 2017. Pumping again ceased in 2018 when ERP Iron Ore LLC entered bankruptcy, and the water level in the pit began rising again.

 

Water level monitoring

Water level elevations through January 2023

Graph of the Canisteo Mine Pit water level elevations since December 1989.

Click to enlarge

The DNR Lands and Minerals Division actively monitors the Canisteo water level and surrounding groundwater levels to understand the rate of pit water level increase and groundwater flow through the subsurface materials. Hydrologic information gathered near the pit informs assessment of the need for an engineered outlet structure to prevent future flooding and other impacts. The city of Bovey drain tile system is monitored for flow and system efficiency. The Canisteo water level trend shown above represents a combination of manual measurements (dashed line) and continuous logger measurements (solid line).

As of January 17, 2023, the Canisteo water level is approximately 1,311 feet, within 13 feet of the natural overflow elevation. There are two natural overflow locations at elevation 1324 feet along the pit rim, one of which is located north of the city of Bovey. Groundwater level monitoring indicates that groundwater outflow from the pit moves to the south. The current hydrologic conditions in nearby communities demonstrate the need to design and construct an engineered outlet for the Canisteo.

 

Winter contingency pumping

The DNR began contingency pumping at the Canisteo to keep water levels below 1,318 feet. Winter pumping ensures the drain tile system in the city of Bovey will continue to divert groundwater away from residential structures. The pumping system is located on the east side of the Canisteo and will draw the water from the pit at a maximum rate of 11,000 gallons per minute. The water is discharged to a wetland complex that flows into Holman Lake.

As water is pumping, water levels at the Canisteo will drop, creating a gap between winter ice cover and the unfrozen water surface, resulting in unsafe ice conditions across the entire pit. Water from the Canisteo will also flow into nearby wetlands and Holman Lake, potentially causing unsafe ice conditions on those waterbodies as well. The DNR strongly advises that all people and recreational vehicles stay off the Canisteo ice, the nearby wetlands, and Holman Lake all winter.

The DNR planned to begin pumping the Canisteo on Oct. 1 but deferred this when DNR invasive species specialists discovered zebra mussels in the pit water in September. To prevent the spread of invasive species downstream, the DNR must ensure that zebra mussel larvae, called veligers, are not present in the Canisteo before water is discharged into surrounding waterbodies. Veligers cannot survive in water temperatures below 53 degrees, so the DNR is pumping in the winter to prevent zebra mussel spread.

DNR experts use a combination of temperature monitoring and water sampling to ensure veligers are not present in the water column before pumping begins, and these studies also determine when pumping should stop before zebra mussel reproductive season begins again. Scientific evidence shows that the zebra mussel reproductive season ends, and live veligers are no longer present in the water column, when water temperatures are below 53 degrees in mid-December through early April.

 

Permanent engineered outlet planning

The $710,000 for contingency pumping at the Canisteo Pit is a short-term solution to prevent water from overtopping the pit until a permanent outlet solution is in place. A permanent solution will require legislative funding. The DNR is continuing work with State agencies, local units of government, and private entities to discuss and plan for the permanent engineered outlet project. A hired consultant is working to finalize the engineering and design, and update plans and specifications for bidding the project.

Once legislative funds are available, construction of the outlet structure is estimated to take one year to complete. If the Canisteo water level continues to rise at a slow rate similar to those in recent years, water may begin to naturally overflow by 2023-2024.

 

Contact

DNR Lands and Minerals Division
St. Paul, MN
651-259-5689