Butte Reduction Works Smelter Area
- Mining waste, tailings, contaminated soils, and slag will be disposed of at a repository outside of the Silver Bow Creek and Blacktail Creek corridors.
- Municipal waste, household waste, timbers, and other construction debris not suitable for re-use will be disposed of at an appropriately permitted facility.
- Any petroleum impacted soil in the excavation area will be properly addressed and removed by Atlantic Richfield Company.
- The reconstructed channel and floodplain of Silver Bow Creek will be sized to accommodate the water flow of a 100-year flood.
- A groundwater hydraulic gradient performance standard of 0.006 foot per foot (0.6%) gradient will be maintained (i.e., groundwater flows toward the capture system) to assess performance of the hydraulic capture system between the creek and the groundwater capture system.
- The BTL may be modified or expanded to provide sufficient capacity to treat additional groundwater captured from the Butte Reduction Works smelter area.
Remedial Construction Activities
The Butte Reduction Works was formerly used for copper, zinc, and manganese production and is currently used by Butte-Silver Bow County to produce asphalt and gravel used in road projects. Years ago, Silver Bow Creek ran through this site.
After the county’s asphalt and crushing operations are moved to another location, the remedy would remove tailings, slag, contaminated soils, and other waste from the southern portion of the site. This will create an average 275-foot-wide corridor to move Silver Bow Creek out of the slag canyon and into the new creek corridor. The land around the new creek will be revegetated. Groundwater controls will be installed to keep contaminated groundwater from discharging to the creek or leaving the site. The remedy will improve surface water quality in Silver Bow Creek and provide the public with an area for possible public recreational use. This site will complete a chain of projects that will provide a continuous link between the proposed remedy at Blacktail Creek and the remedy areas downstream in Silver Bow Creek.
Excavation & Disposal
Approximately 250,000 cubic yards of tailings, waste, contaminated soils and slag will be excavated from the southern portion of the Butte Reduction Works smelter area and hauled to an approved repository for disposal. The excavation footprint would be an average of 275 feet wide and approximately 1,400 feet long. The final depth and removal volume of the excavation will be determined during the design phase of the project.
Groundwater Capture & Treatment
A hydraulic control system will be constructed to capture all contaminated groundwater from discharging to Silver Bow Creek and from leaving the site. This contaminated groundwater will be transported to the Butte Treatment Lagoons (BTL). At the BTL, metal contaminants will be removed, and clean water will be discharged to Silver Bow Creek.
Reconstruct Silver Bow Creek
Following excavation work and installation of the groundwater capture system, Silver Bow Creek and the riparian floodplain will be reconstructed within the excavation footprint through the Butte Reduction Works smelter area. The realigned creek and riparian floodplain will be constructed south of the existing slag canyon and connect with Silver Bow Creek at Lower Area One. The stream and/or floodplain may be lined to enhance the effectiveness of the groundwater capture and treatment system.
End Land Use
The Butte Reduction Works smelter area will be reconstructed in a manner that enables future community use of the site. Atlantic Richfield Company, Butte-Silver Bow, EPA, and MDEQ will work with the residents of Butte to develop an end land use plan that is compatible with the proposed remedy.