Superfund Information Systems: Site Profile

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The Silver Bow Creek/Butte Area site is in and around Butte, Montana, and includes 26 miles of stream and streamside habitat downstream from Butte. Since the late 1800s, mining wastes have been dumped into areas in and around Butte, as well as into streams and wetlands near mining operations, and smelters and mills produced aerial emissions contaminated with arsenic and heavy metals. These activities contaminated soil, groundwater and surface water with heavy metals.

In 1982, EPA proposed the 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. From 1988 to 2005, EPA completed several removal actions to clean up areas around former smelter sites, mine waste dumps, railroad beds, stream banks and channels, and residential yards in Butte and Walkerville to address immediate human health and environmental risks.

Removal and cleanup actions have been completed to address immediate threats to human health and the environment in Butte. Additional cleanup activities, operation and maintenance, sampling, and monitoring actions are ongoing.

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What Has Been Done to Clean Up the Site?

On May 17, 2018, the U.S. Department of Justice and the Atlantic Richfield Company filed a motion to formally request a modification of the confidentiality order. On May 22, 2018, Judge Haddon of the United States District Court for the District of Montana U.S. v. Atlantic Richfield Company et al., the Superfund lawsuit related to the Clark Fork Basin Superfund sites, ordered the modification of the confidentiality order for the Butte Priority Soils operable unit of the Silver Bow Creek/Butte Area Superfund site.

As part of the conceptual agreement reached for the final clean up the Butte Priority Soils Operable Unit (BPSOU) the parties also agreed to file a motion with the Court to modify the confidentially order to allow for public disclosure of information related to the discussion of proposed cleanup activities at the site. The parties agreed that this action was warranted so that the community could be more engaged earlier in this process.

The order resulting from the motion and issued by the Court will allow for the release of major terms of the conceptual agreement that was reached to cleanup BPSOU. It will also provide opportunities for public review and comment of this information and proposed remedy changes before a formal decision is made to modify existing remedies and implement the future work. Future cleanup actions include:

  • The Blacktail Berm, Northside Tailings, and Diggings East tailings, waste, and contaminated soils removals will be performed.
  • Butte Reduction Works (BRW) tailings, waste, sediments and contaminated soils removals to be performed under remedy to provide for a clean floodplain, and the Silver Bow Creek relocation to be reconstructed through BRW corridor.
  • Removal of sediments and floodplain waste along Blacktail Creek from Grove Gulch through the confluence with upper Silver Bow Creek will occur.
  • Parrot Tailings to be removed under State Restoration.
  • Construction of additional stormwater basins and sedimentation bays.
  • Groundwater capture near the visitor’s center and slag canyon to further protect surface water quality.
  • Community visioning and participation to develop end land use options through the corridor.
  • Additional reclamation of mining impacted sites in BPSOU.

View the narrative summaries and other related documents on the proposed future cleanup actions »

Implementation of these provisions of the remedy and the State’s restoration plan will provide a comprehensive cleanup and will conclude over three decades of major removal and remedy cleanup actions projects in the BPSOU.

Over the past 20 years, several cleanup actions have been completed, including removal actions, to address immediate threats to human health and the environment.

Contaminated soil has been removed from waste dumps, residential areas, railroad beds and rail yards. In addition, rail yards and residential properties have been reclaimed, a waste dump has been capped and protected, and cement channels and sedimentation ponds have been put in throughout Butte to address storm water contamination. Contamination has been removed from stream sides and channels and local area groundwater has been treated.

The cleanup plan includes 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; treatment of contaminated surface and groundwater; and long-term environmental monitoring.

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What Is the Current Site Status?

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The Butte Priority Soils operable unit (BPSOU) Record of Decision (ROD) identifies in-stream performance standards for surface water within the BPSOU. EPA and MDEQ have determined that it is necessary to waive and replace certain state surface water standards that prove to be technically impracticable to achieve at BPSOU. Any state aquatic life standard that is waived would be replaced with a federal surface water criterion promulgated under the Clean Water Act for the protection of aquatic life.

A draft Technical Impracticability (TI) Evaluation (PDF) (3,038 pp, 92.5 MB) has been prepared that addresses the issues in more detail.

The draft TI evaluation and the forthcoming proposed plan for a ROD Amendment will be subject to public input and comment before final decisions are made by the agencies. A 60-day public comment period will be announced upon release of the proposed plan, where the public will have several opportunities to provide formal public comment. Current plans anticipate the proposed plan will be released in the spring of 2019. That time frame is subject to revision as EPA and MDEQ go through an internal review process for the proposed plan for a ROD Amendment.

To better address cleanup, the site is currently divided into seven active operable units (OU).

Streamside Tailings OU1 consists of about 26 linear miles of Silver Bow Creek and deposited tailings along the Creek. The boundary begins at the upstream end just outside of the Butte city limits and continues until Silver Bow Creek enters the Warm Springs Ponds. Remedial activities have addressed exposure pathways that could result in unacceptable risks.

Butte Mine Flooding OU3 is the Berkeley Pit and contaminated groundwater in the flooded underground mine workings below the city of Butte and Walkerville. The boundaries are the Continental Divide to the east, Silver Bow Creek to the south, Missoula Gulch to the west, and the Yankee Doodle Tailings Pond and upper Silver Bow Creek to the north.

Rocker Timber Framing and Treating Plant OU7 covers about 16 acres and includes the contaminated groundwater resulting from site operations under and near the land surface. It is located south of U.S. Interstate 15/90 near Rocker, Montana, about 3 miles west of Butte, in Silver Bow County. The community of Rocker is just north of Silver Bow Creek.

Warm Springs Ponds OU4 & 12 is in southwestern Montana at the lower end of Silver Bow Creek approximately 27 miles downstream of Butte. This 2,600-acre area consists of a series of three sediment settling ponds. OU 4 includes the portion that actively treats the entire flow of Silver Bow Creek prior to its confluence with Warm Springs Creek that forms the start of the Clark Fork River. OU 12 is the portion that is not part of the active treatment of Silver Bow Creek Water.

OU8, Butte Priority Soils OU8 (BPSOU): – includes impacted soils, mine wastes, and contaminated attic dust located within portions of the city of Butte, along with mining-impacted alluvial groundwater and surface water associated with the historic and current Silver Bow Creek floodplain within the City of Butte.

In 2011, EPA issued a unilateral administrative order to implement most aspects of the 2006 Record of Decision.

OU13, West Side Soils: includes the mining-impacted areas in and around the city of Butte that are not included in the BPSOU or the permitted active mining area. A comprehensive investigation to characterize the nature and extent of contamination will start in 2018.

Over the timeline of Superfund cleanup in Butte, EPA has completed four five-year reviews to determine how the remedy is working and if it remains protective of human health and the environment. The last Five-Year Review was completed in 2016.

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Sampling and Monitoring

Comprehensive sampling and monitoring actions are ongoing at the site.

The 2008 to 2013 Surface Water Characterization Report (406 pp, 71.4 MB) presents a summary and interpretation of surface water quality data collected at the Butte Priority Soils Operable Unit.

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Emergency Response and Removal

Eleven time‐critical removal actions and expedited response (Non‐Time Critical Response) actions were conducted from 1987 through 2005 to address immediate and significant human health and environmental risks at BPSOU. One removal action, the Lower Area One tailings removal, was a large scale removal of wastes within the Silver Bow Creek floodplain at the site of two former smelters and resulted in substantial improvement to Silver Bow Creek water quality and a reconstructed floodplain.

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Enforcement Information

In 2011, EPA issued a unilateral administrative order (UAO) to implement parts of the 2006 Butte Priority Soils Record of Decision for the portions of the cleanup where there was agreement between EPA and the State of Montana.

In January 2018, EPA, the U.S. Department of Justice, Montana DEQ, Butte Silver Bow, and the Atlantic Richfield Company reached a conceptual agreement to address future cleanup work at the site. EPA will be working with all parties to develop a proposed plan to amend the existing Record of Decision. The proposed plan will be made available for a 60-day public comment period.

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