Canisteo Mine Pit

The DNR has paused construction on the water outlet project at the Canisteo Legacy Mine Pit in Itasca County. While preparing for the construction of the sand filtration system, contractors discovered that the construction area contains material that may impact the existing outlet design. Additional testing is underway to determine if changes to the current design of the outlet system are necessary. Outlet construction will resume once the DNR and contract engineers determine if the system’s design needs to be changed and a plan is in place. This webpage will be updated with new information as it becomes available.

Brief overview

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The Canisteo Mine Pit (Canisteo) is formed by a complex of inactive iron ore mine pits that have filled with water. Located in Itasca County, Minnesota, the Canisteo is 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. To address this, the DNR began monitoring for pit water level and surrounding groundwater changes in 1990 in order to create an important data record from which water level predictions could be made.

An engineered outlet structure is under construction. When it is complete in the summer of 2025, the outlet will control the pit’s water levels year-round to ensure the neighboring communities are not adversely affected. As of May 2025, the Canisteo water level is around 1305 feet, which is 19 feet below natural overflow. Without a permanent outlet, the DNR estimates water would rise at a slow rate, and the pit would naturally overtop. Any runout would be a trickle amount at the lowest elevation of the pit rim at 1,324 feet, which would not pose an imminent threat to public safety and would allow time for the DNR to address the issue.

The DNR and Iron Range Resources & Rehabilitation have been and will continue working with local communities to implement a long-term solution. Legislative funding is now available 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

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

The results of these studies indicated the effects from an 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 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 May 2025

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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 the 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 May 1, 2025, the Canisteo water level is around 1,305 feet, which is 19 feet below natural overflow. Two natural overflow locations at elevation 1,324 feet have been identified along the pit rim, one of which is located north of the city of Bovey. Groundwater level monitoring indicates 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.

The 2023 Minnesota Legislature approved $8.875 million in bonding funds to construct an outlet at Canisteo. The DNR has a contract in place, and construction of a permanent outlet structure is underway to manage Canisteo's water levels.

Water rises in the pit naturally due to rainfall, snow melt, and groundwater. The DNR will continue to manage water levels, if necessary, until the permanent outlet is constructed.

Permanent engineered outlet construction

Contingency pumping at the Canisteo was a short-term solution to manage water levels until a permanent outlet is constructed. In 2023, the Minnesota legislature approved $8.875 million dollars for the construction of an outlet at the Canisteo. Construction on the permanent water outlet structure is underway and is expected to be completed in August 2025.

Once the outlet is completed, water from the Canisteo will flow into the Prairie River. The permanent water outlet will provide year-round water level management, eliminating the need for seasonal pumping.

What is the Canisteo Mine Pit?

The Canisteo Legacy Mine Pit (Canisteo) is a mine pit formed in a complex of several inactive iron ore mine pits in Itasca County north of the cities of Coleraine, Bovey, and Taconite. Active mining operations, including pit dewatering, managed Canisteo water levels. However, mining has ceased, and no company currently manages Canisteo water levels. Over time, the Canisteo’s water levels continued to rise naturally from groundwater and precipitation.

How have Canisteo water levels been managed so far?

In 2022, the Iron Range Resources and Rehabilitation Board funded a contingency pumping project overseen by the DNR. Over two winter seasons, more than 4.7 billion gallons of water were pumped from the Canisteo into nearby Holman Lake and a wetland complex.

Winter pumping kept water levels below 1,318 feet, ensuring that the Bovey drain tile system continued diverting groundwater away from residential structures in Bovey. Seasonal pumping between 2022 and 2024 has controlled Canisteo water levels until an engineered outlet is permanently in place.

Why is the DNR constructing a water outlet at the Canisteo?

Water naturally rises in the pit due to rainfall, snowmelt, and groundwater. Now that no company is actively dewatering the pit for mining operations, the DNR Lands and Minerals Division is closely monitoring both the Canisteo water level and the surrounding groundwater levels. This monitoring provides valuable insight into how the pit water level increases over time. The information collected by DNR staff indicates that we need an engineered outlet structure.

Winter pumping has been a short-term solution to control the water levels at the Canisteo. Now that we’ve secured funding from the legislature, we are breaking ground on a state-of-the-art permanent water outlet. This will allow us to manage Canisteo water levels year-round and prevent water from overtopping the pit without relying on pumping.

Why is DNR pausing construction on the water outlet structure?

While preparing for the construction of the sand filtration system, the contractors discovered that the construction area contains material that may impact the existing outlet design. Additional testing is underway to determine if changes to the current design of the outlet system are necessary. Outlet construction will resume once the DNR and contract engineers determine if the system’s design needs to be changed and a plan is in place. The DNR website will be updated with new information as it becomes available.

How is the water outlet construction funded?

How will the water outlet function?

The outlet system is designed to work with gravity. This means that water from the Canisteo will flow out of the pit all on its own, without needing any pumps. It’s all about the height difference; the water moves because there's a higher point where it starts and a lower point where it will flow into the Prairie River.

We teamed up with contractors to create an outflow system with a sand filtration mechanism. So, when water from the Canisteo flows through the pipeline, it goes through several layers of sand with different grain sizes. This setup acts like a sieve, catching invasive organisms like zebra mussels along the way.

What construction work is happening now?

What about access or recreation near the construction site?

Mine pits are unique features created by mining and aren't natural lakes, which means they might be reopened for mining activities in the future. The future uses of the complex of inactive mine pits in the Canisteo area are still uncertain. If mining resumes here, keeping the site closed is best for private landowners and public safety.

While building the permanent water outlet, you might see contractors using the public roads to get to the Canisteo and nearby areas. If you’re outdoors, keep an eye out for construction equipment or crews in that area. And don’t forget — make sure to get permission from landowners if you’re thinking of exploring any nearby spots.

When will the permanent outlet be completed?

How will Canisteo water levels and temperatures be monitored after the outlet is completed?

Water levels at Canisteo Pit will continue to be monitored while crews are constructing the new water outlet structure. Once the permanent outlet is in place, Canisteo water levels, as well as those downstream at the West Hill and Lind Pits, will be monitored. To keep things safe, the flow route of the Canisteo will need to be monitored for any blockages, preventing possible flooding at culverts or outlet sites. Additionally, the Prairie River flow where the Canisteo outlet discharges will likely be monitored.

At Canisteo, water temperatures will be monitored to determine when to bypass the sand filtration system. During the winter months, when temperatures drop below 50 degrees, water from the Canisteo will not need to be filtered since immature zebra mussels, known as veligers, are usually absent from cold waters.

Biological sampling at Canisteo will ensure that the filtration system effectively filters zebra mussels when water temperatures rise above 50 degrees. This sampling will help determine when the sand filtration system can be bypassed each winter when temperatures fall below this important threshold.

Photos of the permanent outlet construction

The Canisteo Legacy Mine Pit (Canisteo) is a mine pit formed in a complex of several inactive iron ore mine pits including the Lind Pit and the West Hill Pit in Itasca County north of the cities of Coleraine, Bovey, and Taconite.
2025: Construction started this winter with tree removal and land clearing along the entire outlet path.
2025: Construction on the Canisteo Outlet began this winter, starting with moving a stockpile and clearing the land.
Old culverts have been replaced with new, properly sized culverts at the Lind Pit along the outlet route.
Construction crews have been ditching and installing culverts.
Starting in the west and progressing east through the wetland areas, construction crews have been ditching and installing culverts.
Once the outlet is completed, water from the Canisteo will flow into the Prairie River.
Once the outlet is completed, water from the Canisteo will flow into the Prairie River.
Aerial map showing the outlet point from the Canisteo Legacy Mine Pit through the Lind and West Hill Mine Pits and discharged into the Prairie River.

Resources

Contact

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