State and City Respond to Sunset Mine Flooding
Immediate goal is to relieve pressure on bulkhead
By Denise Rivette
Montana Department of Environmental Quality (DEQ) along with the City of Red Lodge and their consultants are responding to the flooding of portions of Sunset Mine, a mine abandoned almost 100 years ago and located just east of Red Lodge Airport. The flooding is affecting nearby landowners and city infrastructure.
The above video shows water being drained from a house basement and the mine itself into the City sewer system. (Denise Rivette)
Water is entering into the basement of a property located at 221 Grant Street in central Red Lodge at an estimated rate of 100 gallons per minute. The problem was discovered during Independence Day festivities and is expected to have occurred on July 3. A City public works investigation indicated the gravity drain that previously carried spring water from within the workings of the mine to the city’s stormwater system has failed. According to the DEQ website, DEQ’s Montana Abandoned Mine Lands Program is responsible for the monitoring and reclamation of Montana’s abandoned coal and hard rock mines.
DEQ issued the following statement:
“The repairs to the gravity drain within the mine workings is a problem DEQ will solve. The department’s Abandoned Mine Lands Program has the ability to complete the work and is proud to support local governments in emergent issues such as this.
DEQ’s singular focus at the moment is to relieve the pressure within portions of the mine to avoid further damages. The department intends to collaborate with local leaders on finding long-term solutions to the problem once immediate concerns are addressed.
Dewatering pumps and gravity flow are currently helping drain the basement and garage of the home into a city sewer drain. The water will be redirected to the stormwater system once upgrades on that section are complete. Testing conducted at the property showed the floodwater’s pH (acidity level) was neutral, indicating spring water that does not pose a threat to human health.
In addition to the flooding of the Grant Street property, responding personnel are concerned that if water pressure continues to build behind the mine bulkhead adjacent to the property, it could result in failure presenting a safety concern.
DEQ, its consultant Olympus Technical Services, and the city of Red Lodge Public Works are prioritizing decreasing the bulkhead pressure to prevent further failure and structure damage. The current plan to address the rising groundwater levels is to excavate into the mine workings to install a temporary drain that will relieve pressure by dewatering the mine.
The city of Red Lodge is working with DEQ’s Abandoned Mine Lands Program to find the best solution to divert the excess water without overwhelming the city’s sewer or stormwater systems. This may include cautionary measures, such as sandbags, piping or other alternatives to handle the excess flow, and piezometers to monitor water levels.
Long-term solutions include the re-installation of a new mine drain connecting to the City’s improved stormwater system, the installation of monitoring wells, and expansion of the city’s stormwater infrastructure.
Please stay away from the area as crews work to solve the issue as quickly and safely as possible.