The Canisteo Mine Pit (CMP) is located north of the cities of Coleraine, Bovey, and Taconite in Itasca County, Minnesota. It is a pit lake formed in a complex of numerous inactive iron ore mine pits.
Mineral exploration began in the area around 1888. Iron ore mining began in the CMP in 1907 and operations continued through 1986. The Mineland Reclamation Rules for ferrous mining were adopted in 1980. These rules require mining operations to plan for closure and reclamation at the onset of mining. After the rules were adopted, from 1980 to 1986 mining consisted exclusively of scram operations, which used previously blasted rock from the pit bottom. Thus, reclamation was only required for disturbances as a result of the scram mining operations. After iron ore mining and subsequent pit dewatering stopped, the pits began to fill with water from precipitation, surface water inflow, and groundwater inflow. The CMP water level began to rise from an approximate pit bottom elevation of 1000 feet above mean sea level (msl) to an elevation of 1317.9 feet msl in July 2012.
Since the majority of the CMP is considered essentially an abandoned mine, there is no private party responsible for water management. The state assumed responsibility for water management and delegated it to the DNR. In 2008, the DNR was allocated funds to address the rising water level of the CMP, including the evaluation of the surficial groundwater flow from the CMP, pitwall instability, and the construction of a potential outlet.
Click to enlarge
As the CMP water level increased, the hydrologic connection between the water level of the CMP and the city of Bovey’s water table became evident. The effects from the already high water table in the western portion of Bovey were worsened by the rising water level in the CMP as water traveled through glacial sediment to the south. To decrease additional groundwater flow toward the city, in 2011 the DNR designed and constructed a drain tile system along 1st Avenue to divert groundwater to Trout Lake. The DNR is responsible for the continued maintenance of the drain tile system. Although designs were completed for the CMP outlet structure, construction was cancelled because of budgetary constraints and a potential for mining operations to use water from the CMP. The remainder of the allocated funds was returned to the State.
In 2012, Magnetation LLC (a subsidiary of Magnetation Inc.) was authorized to pump water from the CMP for mining operations, under a DNR permit. The water was used for two scram mining operations: one located west of the city of Coleraine, the other located south of the city of Taconite. As of August 2016, the CMP water level decreased approximately 20 feet during these operations.
Magnetation LLC filed for Chapter 11 bankruptcy on May 5, 2015. In October 2016, Magnetation LLC ceased pumping activities from the CMP for mining operations.
Should pumping not resume, the CMP will begin to naturally fill with water from precipitation, surface water inflow, and groundwater inflow. Historic data indicate that at the current water level it will take numerous years for the CMP to reach the highest recorded elevation of 1317.9 feet msl. The DNR is actively working with those controlling the Magnetation LLC assets to understand the future plans for the facilities and their role in the CMP water level management.
The DNR will update this status as more information is learned.
Click to enlarge
The DNR actively monitors the CMP water level and groundwater levels surrounding the CMP. The city of Bovey drain tile system is also monitored for flow and system efficiency.
DNR Division of Lands & Minerals
Saint Paul, MN