Region 8

Silver Bow Creek / Butte Area

Silver Bow Creek/Butte Area site location map Site Type: Final NPL
City: Butte
County: Silver Bow/Deer Lodge
ZIP Code: 59701
EPA ID: MTD980502777
SSID: 0822
Congressional District: At Large

What's New?

Updated July 2014

EPA, in consultation with the Montana Department of Environmental Quality, has approved the Butte Priority Soils Operable Unit Public Health Study, Phase 1 Report. The report includes the response summary for comments received in Appendix B.

The 2002 Consent Decree for the Butte Mine Flooding Operable Unit (BMFOU) requires that the Settling Defendants submit quarterly reports. To achieve compliance, the Settling Defendants conduct remedial action activities under the seven components identified in the Statement of Work attached to the Consent Decree. The quarterly reports are a great resource for up to date information about the:

  • Monitoring Program
  • Horseshoe Bend Water Treatment Plant
  • West Camp System
  • Waterfowl Mitigation
  • Slope Stability

For more information about the BMFOU and the Berkeley Pit, visit the PitWatch website.

Bulletin #19 – Butte Priority Soils OU Remediation, July 11, 2013

EPA has issued an Explanation of Significant Differences (ESD) to the 2006 Record of Decision (ROD) for the Butte Priority Soils Operable Unit (BPSOU). An ESD is a type of ROD modification that documents and explains significant changes in the remedial approach at the site. The significant changes in the 2011 ESD do not fundamentally alter the overall approach of the BPSOU remedy. The ESD is posted in Site Documents below. It may also be viewed in hard copy at the information repositories listed below.

Five-Year Review Completed

The third five-year review report for the Silver Bow Creek/Butte Area Superfund Site was signed on June 27, 2011. You may view the report in the Site Documents section below. Hard copies of the report can be viewed at three EPA information repositories: the EPA Butte Office at 400 North Main Street, Room 339; the CTEC Office at 27 West Park Street; and the EPA Helena Office at 10 West 15th Street, Suite 3200.

Consent Decree

Consent decree negotiations are ongoing between the potentially responsible parties and the government. Because of the confidential nature of negotiations, the various government staff members working on the Silver Bow Creek/Butte Area site may not discuss the topics being negotiated. You may still call government staff but please understand that there may be topics that are off limits until the CD negotiations conclude. Please also feel free to contact your community technical assistance group TAG for information on how you can get involved.

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Site Description

The boundary of the Silver Bow Creek/Butte Area site begins above Butte, near the Continental Divide, and extends westward along Silver Bow Creek to and including the Warm Springs Ponds (a treatment area). The site covers about 26 miles of stream and streamside habitat. Silver Bow Creek was used as a conduit for mining, smelting, industrial and municipal wastes for more than a hundred years. Vast mine tailings deposits are found along the creek. These deposits contain elevated levels of metals and have been dispersed over the entire flood plain. The site also includes the cities of Butte and Walkerville, as well as the Berkeley Pit and the interconnected mine workings.

Map of the Superfund site boundary, March 2007

The Silver Bow Creek/Butte Area site is one of four contamination areas, jointly known as the Clark Fork Basin Sites. Others are Milltown Reservoir Sediments, Anaconda Company Smelter, and Montana Pole & Treating Plant. All are on EPA's National Priorities List.

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Site Risks

More than 100 years of mining have resulted in the development of over 500 underground mines (with roughly 3,000 miles of underground workings) and four open pit mines, including the Berkeley Pit with its ancillary tailings ponds, waste dumps and acid leach pads. Operation of silver mills and copper and zinc concentrators/smelters in Butte resulted in the production of a variety of mill and smelter wastes, including particulates (aerial emissions and tailings). The long period of mining in Butte left the landscape littered with un-vegetated or sparsely vegetated mine wastes, often containing hazardous concentrations of metals and arsenic. These wastes represent significant sources of environmental contamination to Silver Bow Creek and posed human health and risks to the environment.

Groundwater, surface water and soils are contaminated with arsenic and other heavy metals, including copper, zinc, cadmium and lead. Silver Bow Creek and the Clark Fork River contain metals from the cities of Butte to Milltown. The tailings, dispersed along the creek and river, severely limit aquatic life forms and have caused fish kills in the river. Potential health threats include direct contact with and ingestion of contaminated soil, surface water, groundwater or inhaling contaminated air.

Butte-Silver Bow County currently has a very successful Residential Metals and Abatement Program. The county's abatement program removes both mining-related and non-mining-related sources of lead (such as lead-based paint and piping) from residential properties where children live. The county has implemented the program since 1995 and there has been a significant drop in blood lead levels in the community. See the Residential Metals and Abatement Plan in Site Documents below or at the site information repositories. For more information on this program, call Eric Hassler at the Butte-Silver Bow County Health Department at 406-497-5042.

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Cleanup Progress

EPA has completed several removal actions and is now focusing on cleanup of the rest of the Butte Priority Soils Operable Unit through long-term remedial response actions.The long-term response actions are documented in a 2006 Record of Decision, which is posted in Site Documents and available in hard copy at the information repositories.

Removal Actions

1988 - Walkerville (north of Butte): Stabilization of 300,000 cubic yards of lead-contaminated soil from mine waste dumps. Earthen basements (four) and residential yards (23) were cleaned up.
1989 - Timber Butte: Some 40,000 cubic yards of contaminated soil were moved to a temporary on-site repository. Two residential yards were cleaned up.
1990 - 1991 Priority Soils: Waste dumps containing about 100,000 cubic yards of soil were either capped or removed. A railroad bed and seven residential yards were also reclaimed.
1991 - Colorado Smelter: Approximately 40,000 cubic yards were moved to an on-site disposal area.
1992 - Anselmo Mine Yard/Late Acquisition Silver Hill: contaminated soils were removed.
1994 - Walkerville: Several waste dumps were either removed or capped.
1994 - Residential/Source Areas: Residential yards and waste rock dumps located throughout Butte and Walkerville have been/are being addressed.
1996 - Stormwater: Construction of cement channels and sedimentation ponds throughout the Butte hill to address stormwater contamination.
1999 - Railroad: Removal of contaminated soil on numerous railroad beds and rail yards throughout the Butte hills.
2000/2001 - Walkerville Residential Area: This action addressed 46 residential properties throughout the community of Walkerville.

Long-Term Remedial Response

Warm Springs Ponds
The three man-made Warm Springs Treatment Ponds cover 2,500 acres at the confluence of four main tributaries of the upper Clark Fork River. From 1990 through 1995, three separate Superfund response actions were carried out by the ponds' owner and system operator, the Atlantic Richfield Company, with oversight by EPA.

Tailings were removed from the Mill-Willor Bypass and consolidated behind armored, reinforced berms. The lime treatment plant and hydraulic structures were upgraded. Large areas of exposed tailings were capped or flooded. Waterfowl ponds and wetlands were constructed throughout the pond and bypass system.

Water quality and biological health of the upper Clark Fork River improved within the first few years after the three response actions were constructed and operational. Over the past 15 years, the treatment system's capabilities for removing toxic levels of heavy metals from Silver Bow Creek have become increasingly effective. The effects of heavy metals are minimized by physical settling of sediments within the two large treatment ponds, Ponds 3 and 2. Metals change from a dissolved to a particulate phase when the pH of the water is raised to an optimum level between 9.2 and 9.4. This is accomplished by adding lime at the point where Silver Bow Creek enters the treatment system slightly upstream of Pond 3, or by the natural bloom of algae in the ponds.

The Warm Springs Ponds' outgoing flows meet water quality criteria for trout and sensitive invertebrates 99 percent of the time. Immediately upon exiting the pond system, outflows combine with Mill and Willow creeks and, within one-half mile, Warm Springs Creek (all creeks generally have good to excellent water quality). The confluence of these creeks forms the upper Clark Fork River.

Although metals are effectively removed, arsenic responds differently. Fortunately, aquatic organisms are not highly affected by the moderate levels of arsenic present. Arsenic concentrations do exceed drinking water standards, both above and below the pond system; however, humans are not exposed because the affected streams are not sources of drinking water.

Biological monitoring within the past three to four years suggests that increasing levels of ammonia may be largely responsible for reduced biological health of fish and aquatic organisms in the stream reaches immediately below the ponds. Good to excellent biological health was observed for several years after completion of the treatment; more recently it has become "slightly impaired." EPA, MDEQ and Atlantic Richfield Company have undertaken additional studies designed to better understand nutrient cycling due to the influence of upstream nutrient inputs and other factors. Whenever ponds, reservoirs or lakes can no longer cycle, or metabolize nitrate or phosphate that enters them, they undergo a process termed eutrophication. This process leads to excessive plant buildup and the release of ammonia.

Warm Springs Ponds OU, Annual Summary Graphs and Tables for 2010 (in Site Documents below) presents tables and figures that compare incoming and outgoing concentrations of key metals, arsenic, suspended sediments, pH, etc. against criteria for protection of aquatic life.

Butte Priority Soils
The Butte Priority Soils Operable Unit was divided into two phases. Phase I, an expedited Response Action, addressed source areas by removing waste dumps, railroad beds or other related mine wastes. Response actions that are part of Phase I continue. Phase II is the final remedial process to address the remaining environmental and human health issues associated with all the media including soil, groundwater and surface water. Phase II culminated in a Record of Decision in September 2006, which is posted in Site Documents or can be viewed in hard copy at the site information repositories.

West Camp/Travona Shaft Area
In 1989, rising mine waters were addressed by a pumping and piping system, sending the waters to the Metro Plant and preventing basement flooding and discharges of contaminated groundwater to the alluvial aquifer and Silver Bow Creek.

Berkeley Pit
EPA and the state are concerned about rising contaminated mine water in the pit because the water may eventually migrate into the shallow aquifer and Silver Bow Creek. Clean up plans include: 1) Permanent control of surface inflow into the pit; 2) Maintenance of the water level in the Berkeley Pit system; 3) Continued control of the West Camp/Travona System; 4) An extensive compliance monitoring program; and 5) Institutional controls.

Rocker Timber Framing and Treating Plant
In 1995, EPA, working with MDEQ, selected the remedy to address human health risks from potential exposure to contaminated soils and groundwater. Cleanup occurred in 1997. EPA is in close communication with the Rocker Water Board and the Butte Silver Bow County Health Department.

Streamside Tailings
In November 1995, EPA and the MDEQ selected a remedy for the Streamside Tailings area. An Explanation of Significant Differences (ESD) adjusted the remedy to some extent. The remedy removes much of the waste along the creek and treats other waste in place. Construction began in fall 1999 and is progressing well in Sub-Area 1 in the upper portion of SBC.

Lower Area One
EPA conducted an Expedited Response Action for this area. In 1992, EPA removed manganese stockpiles, and in 1993-1997 removed mine tailings (Colorado and Butte Reduction). A groundwater collection and treatment system has been installed. Studies are underway to see if additional cleanup is necessary.

Final capture and treatment of contaminated groundwater is planned, and the final cleanup decisions are part of the Butte Priority Soils Record of Decision.

Environmental Progress

Numerous completed cleanup actions at the Silver Bow Creek/Butte Area site have reduced human exposure to metals and other health threats. However, EPA has determined that high concentrations of metal in soils and drainage from the smelter still pose risks that will be addressed in future cleanup actions.

Activities for 2011 include:

1. Construction completion for:
    – Granite Mountain Memorial Interpretive Area.
    – Syndicate Pit.
    – Remaining source areas.
    – Lower Area One.

2. Continue stormwater monitoring program.

3. Continue groundwater monitoring program:
    – Installation of additional groundwater monitoring wells near Metro Storm Drain and Lower Area One.

Future Activities

4. Evaluation of the Metro Storm Drain and treatment lagoons at Lower Area One.

5. Implementation of Best Management Practices (BMPs) for stormwater.

6. Implementation of the Butte Reclamation Evaluation System.

7. Consent Decree negotiations or Administrative Order is served by EPA.

8. Continued implementation of the Residential Metals Abatement Program.

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Five-Year Reviews

EPA or the lead agency conducts five-year reviews following the start of a Superfund cleanup when contamination is left on the site. These reviews are repeated every five years. We use these reviews to determine:

  • How the remedy is working
  • If the remedy remains protective of human health and the environment

EPA has completed the third five-year review of the Silver Bow Creek/Butte Area site. The report is posted in Site Documents below or available in hard copy at three information repositories: the EPA Butte Office at 400 North Main Street, Room 339; the CTEC Office at 27 West Park Street; and the EPA Helena Office at 10 West 15th Street, Suite 3200.

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Site Documents

Note: best way to open a very large file: right-click and save it to a folder.

You will need Adobe Reader to view some of the files on this page. See EPA’s About PDF page to learn more.

Monthly Progress Reports – Butte Priority Soils Operable Unit

Atlantic Richfield

Butte-Silver Bow County

BNSF/Union Pacific

Quarterly Progress Reports – Butte Mine Flooding Operable Unit

Settling Defendants' Quarterly Reports


Bulletin #18 – Residential Metals Program Outreach, April 2, 2012

Bulletin #17 – West Camp Pump Station & Hydrodynamic Devices, February 13, 2012

Bulletin #16 – 2011 Winter Updates, November 28, 2011

Bulletin #15 – Summer Summary 2011, September 21, 2011

Bulletin #14 – 2011 Unilateral Administrative Order (UAO) & Work Plan, August 10, 2011

Bulletin #13 – 2010 Residential Metals Abatement Program Activities, April 6, 2011

Bulletin #12 - Community Engagement & EPA's New Office, February 23, 2011

Bulletin #11 - CTEC and TAG, January 26, 2011

Technical Documents

Note: the five-year review is broken up into volumes by Operable Unit. The following volumes and all appendices are located on our publicly accessible FTP site:

Warm Springs Ponds Operable Unit, Annual Summary Graphs and Tables for 2010, March 31, 2011

Group 1 Settling Defendants' Institutional Control Plan, March 2010

Decision Documents

Explanation of Significant Differences to the 2006 Butte Priority Soils Operable Unit Record of Decision, July 2011

Butte Priority Soils Operable Unit Record of Decision, September 2006

Past Records of Decision for this site

Other Documents

Butte Priority Soils Operable Unit, Public Health Study Phase 1 Report, July 2014

Butte Priority Soils Operable Unit, Public Health Study Remedial Design Work Plan, Phase 1 Study, May 2013

2012 Data Summary: Butte Mine Flooding Operable Unit, March 2013

Community Involvement Plan: Butte Priority Soils Operable Unit, February 2013

2010 Ground Water Data Analysis Report, February 1, 2012

Residential Metals Abatement Plan, April 2010

Summary of EPA’s Record of Decision for Cleanup of the Butte Priority Soils, September 2006

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Sara Sparks
Remedial Project Manager
U.S. Environmental Protection Agency, Region 8
Butte Office
400 North Main Street, Room 339
Butte, MT 59701

Kristine Edwards
Remedial Project Manager for Warm Springs Ponds
U.S. Environmental Protection Agency, Region 8
Helena Office
Federal Building
10 West 15th Street, Suite 3200
Helena, MT 59626

Nikia Greene

Remedial Project Manager for Rocker and Mine Flooding
U.S. Environmental Protection Agency, Region 8
Helena Office
Federal Building
10 West 15th Street, Suite 3200
Helena, MT 59626

Montana DEQ

Joe Griffin
State Project Officer
Montana Department of Environmental Quality
P.O. Box 200901
Helena, MT 59620-0901

Daryl Reed
State Project Officer for Warm Springs Ponds, Rocker and Mine Flooding
Montana Department of Environmental Quality
P.O. Box 200901
Helena, MT 59620-0901

Joel Chavez
State Project Officer for Streamside Tailings
Montana Department of Environmental Quality
P.O. Box 200901
Helena, MT 59620-0901

Site Information Repositories:

EPA Butte Office

400 North Main Street, Room 339
Butte, MT 59701

EPA Superfund Records Center
Montana Office
10 West 15th Street, Suite 3200
Helena, MT 59626
866-457-2690 (toll free)
Hours: M-F, 8:00 a.m.-4:30 p.m.

Community Groups

Citizens Technical Environmental Committee (CTEC)
Dr. John W. Ray, President
Janice Hogan, TAG Administrator
27 West Park Street
P.O. Box 0593
Butte, MT 59703-0593

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The following links exit the site Exit

PitWatch (Berkeley Pit Public Education Committee)

Citizens Technical Environmental Committee (CTEC)

Atlantic Richfield's Butte Cleanup Data Site

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