Buffalo Gulch Area
- Wastes will be removed to the depth of the most recently observed 3-year maximum groundwater elevation.
- Mining waste, tailings, and contaminated soils 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.
- The stormwater detention/retention basin would be sized to capture a 10-year, 24-hour Type I Soil Conservation Service (SCS) design storm. This will allow for capture and treatment of 20 acre-feet (approximately 6.5 million gallons) of stormwater. Additional storage volume will be provided to support management of accumulated sediments.
Remedial Construction Activities
The remedy will remove tailings, wastes, and contaminated soils from an approximately 9-acre site located at the bottom of Buffalo Gulch and will construct a stormwater basin in the excavated area to reduce the amount of contaminated sediment and metals that reach Silver Bow Creek and improve the quality of water in the creek. The remedial activities will be performed by Atlantic Richfield Company and will include:
Excavation & Disposal
Approximately 30,000 cubic yards of tailings, wastes, and contaminated soils, including municipal wastes, will be excavated from the site and hauled to a repository. Some excavated materials, including uncontaminated soil (from previous reclamation activities) and small concrete, will be reused to complete reconstruction of the site.
A stormwater basin will be constructed to capture stormwater from the Buffalo Gulch drainage to improve water quality before it enters Silver Bow Creek. The stormwater basin is currently anticipated to be fully lined and will be designed to cover about 8 acres (about six football fields), which is a sufficient size to manage stormwater and accumulated sediments. Maintenance of the basin will include removal and disposal of captured sediments at a repository.
End Land Use
The Buffalo Gulch area will be reconstructed in a manner that enables future community use of the site and land around the stormwater basin. Although the basin is expected to occupy most 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 remedy.