Please stay off the ice at the Canisteo Mine Pit, Holman Lake, or the surrounding wetlands.
The Canisteo is undergoing pumping right now to lower its water level, and that is expected to create some serious ice safety issues.
Water is being pumped from the Canisteo (and into the wetlands that lead into Holman Lake) up to a maximum rate of 18,000 gallons a minute. Once ice forms on the Canisteo, there is expected to be gaps between the ice and the unfrozen water underneath —known as an “ice shelf”— and if you fall through it’s nearly impossible to rescue yourself.
Watch this ice safety video to learn more about what's happening and why it's important to stay OFF the ice on the Canisteo as well as Holman Lake, and the nearby wetlands this winter.
Brief overview
The Canisteo Legacy Mine Pit (Canisteo) is formed by a complex of inactive iron ore mine pits that have filled with water. The Canisteo is located in Itasca County, Minnesota, 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 necessary to control the pit's water levels in a way that doesn't adversely affect surrounding communities. As of March 2024, the Canisteo water level is around 1,306 feet, which is 18 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 the Department of Iron Range Resources & Rehabilitation (DIRRR) 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
After iron ore mining and subsequent pit dewatering ended, the Canisteo began to fill with water from precipitation as well as 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 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
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 March 14, 2024, the Canisteo water level is around 1,306 feet, which is 18 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 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.
Looking ahead, the DNR is dedicated to continued monitoring, evaluation and implementation of a permanent outlet structure to manage Canisteo water levels. The Minnesota Legislature has appropriated funding for construction of the Canisteo outlet, so the next step is for DNR staff to bid out construction of the fully designed outlet project, which will include further dewatering of the pit.
Water rises in the pit naturally due to rainfall, snow melt and groundwater. The DNR will continue to manage water levels until the permanent outlet is constructed.
Winter contingency pumping
The DNR resumed seasonal pumping at the Canisteo Legacy Mine Pit (Canisteo) in Itasca County. Pumping this winter will keep water levels below 1,318 feet where the drain tile system continues to divert groundwater away from residential structures located in Bovey. Additionally, lowering water levels as much as possible is essential to preparing for construction and minimizing overall costs for the permanent outlet structure.
The pumping system is located on the east side of the Canisteo and will draw the water out from below the Canisteo's surface up to a maximum rate of 18,000 gallons per minute. The current pumping volume is occurring at a higher rate than last year in order to prepare for construction of the permanent outlet. The water will then be discharged to a wetland complex that flows into Holman Lake in Itasca County.
Once pumping begins, Canisteo water levels could drop rapidly, creating a gap between winter ice cover and the water's surface below, resulting in unsafe ice conditions across the entire pit. Water from the Canisteo will flow into the nearby wetlands and Holman Lake, which may also cause unsafe ice conditions on those water bodies. The DNR strongly advises that all people and recreational vehicles stay off the ice at the Canisteo, nearby wetlands and Holman Lake all winter.
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 water bodies. Water sampling has documented that zebra mussel's reproductive season ends during winter months when water temperatures are consistently below 53 degrees. When water temperatures are low, live veligers, which float in the water and can be moved by water currents, are not present in the water column. Therefore, confining pumping to the winter months avoids the need for additional filtration or treatment.
DNR experts use a combination of temperature monitoring and water sampling to ensure veligers are not present in the water column before pumping begins. This information also determines when pumping should stop before zebra mussel reproductive season resumes.
Permanent engineered outlet planning
Contingency pumping at the Canisteo is a short-term solution to manage water levels until a permanent outlet is constructed. The 2023 legislature approved $8.875 million dollars for construction of an outlet at the Canisteo, which is already completely designed, to provide permanent and year-round water level management, as well as the removal of invasive species.
The construction plans will go out for bid in the spring of 2024, and construction could potentially start later that year. The outlet is designed to be a natural gravity outflow system with built in sand filtration to prevent the transfer of zebra mussels to downstream waterbodies. Water from the Canisteo will ultimately flow into the Prairie River.
Additional dewatering is necessary to make room for construction of the outlet. Residents of Coleraine, Bovey and Taconite should be aware that ongoing dewatering and construction activities will impact recreation on or near Canisteo.
Contact
DNR Lands and Minerals Division
St. Paul, MN
651-259-5689