The St. James Mine Pit (St. James) is located north of the city of Aurora in St. Louis County, Minnesota. Natural iron ore was mined from the St. James and shipped between 1916 and 1963.
The Mineland Reclamation Rules for ferrous mining were adopted in 1980 and require mining operations to plan for closure and reclamation at the onset of mining. However, because mining in the St. James ceased prior to the Mineland Reclamation Rules, no company is responsible for reclamation of the site, which may include water level management.
Currently, the city of Aurora utilizes the pit water for the city’s municipal water supply. The city’s municipal water supply pump house (pump house) is located several feet above the current water level. The water level elevation was 1441.65 feet above mean sea level (msl) on January 30, 2019 with the pump house floor elevation at 1444.27 feet msl.
Water is supplied to the city by pumping from a large well located in the pump house. The well is directly connected to the pit through an underground pipe. Thus, water levels measured in the city’s well is approximately equivalent to the pit water level elevation.
St. James water level management
Though water from the St. James is used for the city of Aurora’s water supply, the demand is less than inflows to the pit resulting in rising water level. The pit receives water from precipitation, surface water inflow, and groundwater inflow. Rising water in the St. James has prompted the city to manage water levels to protect their pump house from flooding.
As the St. James continues to gain water, an engineered outlet and route may be needed in the future to prevent flooding. To enable informed discussion with state leaders and legislators, a number of state agencies are collaboratively working to gather data. The initial data gathering will be to collect water quantity and water quality information from the pit as well as potential nearby surface waters which may be receiving waters in various designed outlet scenarios.
Future work may include but is not limited to continuation of water level monitoring, bathymetric surveying, installation of groundwater wells, surveying of outlet route, and construction of a groundwater model.
Once a preferred outlet location and route are chosen, future phases would include engineering a design and then construction. Future data gathering, engineering design, and construction would need to be funded before these phases of the project could move forward.
Water Level Elevations through 1/30/2019
Water level monitoring
The DNR Division of Lands and Minerals installed equipment in the pump house well to measure water levels which will help inform the rate of water level increase. The downward trends in water level are from the water level maintenance pumping the city has undertaken. If the water level maintenance pumping were to be turned off the water level would continue to rise within the pit. The St. James water level trend shown represents a combination of manual measurements and continuous logger measurements.
DNR Division of Lands & Minerals
St. Paul, MN