Background
Background
The Silver Bow Creek/Butte Area site is in and around Butte, Montana, covers approximately 85 miles, and includes 26 miles of westward-flowing stream and streamside habitat downstream from Butte.
Mining activities occurred in Butte, Montana, and in surrounding areas for over 100 years. Underground mining was extensive in Butte and Walkerville. Silver milling, followed by the extensive operation of copper and zinc smelters and mills, generated a variety of wastes. By the late 1880s, Butte became one of the nation’s prominent copper mining centers. Mining crews disposed of wastes generated from mining, milling and smelting operations directly into Silver Bow Creek and Blacktail Creek and across the Butte Hill. These waste disposal practices contaminated soil, sediment, groundwater and surface water with arsenic and heavy metals, leaving the natural landscape largely devoid of vegetation and wildlife. Meanwhile, smelters and mills produced aerial emissions contaminated with arsenic and heavy metals.
In 1982, EPA proposed that Silver Bow Creek be added to the National Priority List (NPL), and it was listed as a Superfund site in 1983. Butte Area was added to the Silver Bow Creek site in 1987. The Site includes Silver Bow Creek, the Berkeley Pit and the underground mine workings of the historic Butte Mining District (Butte Hill), the urban centers of Butte and Walkerville, rural areas outside of Butte where mining took place, and the treatment/settling ponds at the Warm Springs Ponds.
Screening studies and risk assessments identified contaminants of concern (COCs) and quantified human health and environmental risks from these COCs in solid media (including tailings, waste, sediment, soils and indoor dust), surface water and groundwater.
To address and manage cleanup activities, the site is currently divided into seven active operable units (OUs);
- Streamside Tailings OU1,
- Butte Mine Flooding OU3,
- Rocker Timber Framing and Treating Plant OU7,
- Warm Springs Ponds OU4 and 12,
- Butte Priority Soils OU8 (BPSOU), and
- West Side Soils OU13.
Through operable unit (OU)-specific Remedial Investigation / Feasibility Studies (RI/FS), OU-specific action levels have been established for site COCs in decision documents (e.g., record of decision). Coordination of cleanup among all the OUs is managed by different Site Remedial Project Managers (RPMs), who manage and approve investigations, design plans for cleanups, oversee cleanup actions, and consult with state partners. Cleanup activities, operation and maintenance, sampling, and monitoring actions are ongoing.
What Has Been Done to Clean Up the Site?
EPA oversees the majority of cleanup activities in Butte. In other areas, the State of Montana is overseeing cleanup. Cleanup actions and activities so far on the site have included:
- Assessments of risk to quantify actual and potential human health risks due to potential exposure to tailings, waste rock, yard soils, indoor dust, attic dust, mercury vapor, surface water, and ground water.
- Removal of tailings, contaminated soils, and sediment, and placement of these materials in managed repositories.
- The establishment of vegetation, especially in the Blacktail and Silver Bow Creek Corridors.
- Construction of water treatment plants and treatment of contaminated water.
- Source area controls and capping of contaminated waste dumps and railroad beds.
- Revegetation and the establishment of vegetation with associated standards that allow for long term monitoring and maintenance to meet performance standards in the Butte Reclamation Evaluation System (BRES).
- Installation of storm water controls.
- Capture and treatment of ground water.
- Alternative water supply systems and controlled ground water areas for the community.
- Institutional controls, including controlled groundwater areas, excavation and dirt-moving ordinances, and stormwater management protocols.
- Implementation of the Residential Metals Abatement Program (RMAP) that provides comprehensive assessment and remediation of lead, arsenic, and mercury in residential yards, interior dust, paint, and pipes.
- Medical monitoring to test residents for blood lead and urine arsenic.
- Removal actions to address immediate threats to human health and the environment.
- Ongoing community education and engagement, including community meetings, implementing the site-specific environmental plan, attending design workshop updates with Butte-Silver Bow County.
Cleanup plans include further removal of lead- and arsenic-contaminated soil and attic dust in homes and yards; removal of contaminated soil, sediment and tailings from around Butte; placement of contaminated materials in repositories; management of remaining wastes left in place; institutional controls; long-term operation and maintenance; stormwater management; treatment of contaminated surface and groundwater; and long-term environmental monitoring.
View narrative summaries and other related documents in the Records Collection.