About Us



Gold is discovered in Butte; a mining camp is formed.



1860s – 1890s

Silver production expanded and then declined when the silver market collapsed.



1870s – Current

Copper is mined in Butte.



1875 – 1955

Large-scale underground mining in Butte.



1870s – 1945

This period constituted the “heyday” of milling and smelting in Butte. Silver milling boomed first, from the 1870s through about 1893. Large-scale copper smelting started around 1880, reached its peak in the 1890s, and ended in 1924. Zinc milling started small in 1905, and expanded greatly prior to and during the World War I era, closing out by 1930. Manganese was processed from 1928 through the end of World War II in 1945.




The Anaconda Copper Mining Company (ACMC) incorporated.




ACMC changed its name to The Anaconda Company; open pit mining began in the Berkeley Pit (adjacent to the BPSOU).




The majority of The Anaconda Company’s global assets, in Chile and Mexico, were seized by foreign governments and nationalized.




Atlantic Richfield Company purchased The Anaconda Company.




Smelting operations in Anaconda closed.




The Anaconda Company merged with Atlantic Richfield.




Atlantic Richfield Company suspended its mining activity in Butte and offers its Butte mining business for sale. EPA placed Silver Bow Creek Site and associated areas on its national priority list of sites for investigation and remediation under the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA).




The Butte mining business was purchased by Dennis Washington and Montana Resources Inc.




Mining operations resumed in the Continental Pit (formerly known as the East Berkeley Pit) under new mine ownership.




The Silver Bow Creek Site was modified by EPA to include the Butte area, and the site is renamed “Silver Bow Creek/Butte Area NPL Site.” EPA begins conducting and ordering responsible parties to conduct strategic removals and expedited response actions to reduce potential exposure to mining waste.




Atlantic Richfield removes ~300,000 cubic yards of mine waste under the Walkerville Time Critical Removal Action (TCRA).




Atlantic Richfield completes the Timber Butte TCRA, addressing 40,000 cubic yards of contaminated soil.




Remedial investigation and feasibility study investigations begin in the 1990s. Thirty waste dumps are addressed by Atlantic Richfield under the Butte Priority Soils TCRA, resulting in removal or remediation of 100,000 cubic yards of waste.




Atlantic Richfield removes and consolidates ~40,000 cubic yards of impacted materials under the Colorado Smelter TCRA. The Lower Area One Expedited Response Action (ERA) is initiated by Atlantic Richfield, eventually removing over 1 million cubic yards of accessible mine waste and tailings along Silver Bow Creek.

A consent order with EPA is signed by Atlantic Richfield and other potentially responsible parties (PRPs) to conduct a Remedial Investigation/Feasibility Study (RI/FS).




Walkerville TCRA II is completed by Atlantic Richfield, addressing 12 additional waste dumps. The Butte Priority Soils ERA for Residential Soils/Source areas begins, leading to ongoing metal abatement for contaminated residential yards and attics under what is now referred to as the Residential Metals Abatement Program (RMAP).




Atlantic Richfield begins work under the Stormwater TCRA to control stormwater flow, minimize erosion, and reduce transport of contaminated sediment to Silver Bow Creek. Work included reclamation of the Alice Mine dump, reclaiming ~ 2,000,000 cubic yards of contaminated soil and waste rock.




Phase I of the BPSOU Remedial Investigation and Feasibility Study (RI/FS) is completed. Atlantic Richfield enters into agreements with the U.S. EPA, State of Montana and other trustees on certain natural resource damages and remediation claims relating to Clark Fork River Basin sites.




The Court approves settlements among Atlantic Richfield, the State, and the U.S. to resolve: some claims for natural resource damages and restoration activities in portions of the Clark Fork Basin, claims for remediation of most of Silver Bow Creek, and past costs incurred during litigation. Further information can be found on the Administrative and Judicial Proceedings webpage.




Atlantic Richfield opens the Copper Mountain Sports and Recreation Complex to the public.




Phase II of the BPSOU RI/FS is completed.




Atlantic Richfield begins construction of the Metro Storm Drain (MSD) subdrain system, now referred to as “upper Silver Bow Creek,” that captures contaminated groundwater beneath the upper Silver Bow Creek corridor for treatment at the Butte Treatment Lagoons system




The remainder of the BPSOU RI/FS is completed. EPA releases proposed plan for remediation in the Butte and Walkerville areas.




U.S. EPA issues a Record of Decision (ROD) containing the selected, final remedy for BPSOU. Butte-Silver Bow County (BSB) and Atlantic Richfield reach an agreement that provides funding to BSB to complete certain portions of the remedy. The Butte Historic Landmark District is expanded. Design and construction of the final BPSOU remedy begin. The Butte lead abatement program is re-named the “Residential Metals Abatement Program,” building on the multi-pathway program initiated by U.S. EPA with funding from Atlantic Richfield in 1994, in cooperation with Montana DEQ and Butte-Silver Bow County.

Butte Reclamation Evaluation Program begins.




Upgrades of the subgrade vault pumping system and control building of the MSD subdrain system are completed by Atlantic Richfield.

The State, the U.S., and Atlantic Richfield reach a final settlement for remediation of the upper Clark Fork River site and settle all remaining State claims for natural resource damages and restoration costs for Butte Area One, the Smelter Hill Uplands, and the upper Clark Fork River.




Atlantic Richfield begins cleanup and redevelopment construction of Mountain Con Mine Yard.




Atlantic Richfield completes the Granite Mountain Memorial and begins Silver Bow Creek stream bank and floodplain removal near the confluence with Blacktail Creek.

Atlantic Richfield expands groundwater capture system of Lower Area One during the Butte Reduction Works Open Area Excavation project.

EPA reports that the majority of capping is complete.




EPA issues a BPSOU Unilateral Administrative Order to Atlantic Richfield and Butte-Silver Bow, with additional remedy analyses and requirements that are needed to complete the 2006 BPSOU ROD remedy. Atlantic Richfield begins to upgrade the Butte Treatment Lagoons and West Camp Pump Station, modernizing the groundwater collection and treatment system at Lower Area One.




Atlantic Richfield opens Foreman’s Park and recreation area at the Mountain Con Mine Yard and completes a one-mile extension of Mine Yard and Butte Hill Trail system.




Atlantic Richfield begins the Lower Area One Surface Enhancements to improve vegetative cover throughout Lower Area One.




Atlantic Richfield completes demolition and reclamation of the former Wetland Demonstration Area, covering approximately eight acres in the center of Butte.




Atlantic Richfield begins reclamation and preservation of the historic Lexington Hoist House and Mine Yard.




EPA releases potential concepts for modifications to the 2006 BPSOU ROD remedy for public review and comment. Details can be found on the Completing the remedy page of this website.




April 11—EPA publishes an amended proposed remedy plan for BPSOU, for public review and comment. The comment period closed on July 11, 2019.




February 4—US EPA releases an amended Record of Decision for the Butte Priority Soils Operable Unit and portions of the Butte Area site.

February 13—US EPA, the State of Montana, the consolidated City and County government of Butte-Silver Bow (BSB) and Atlantic Richfield Company announce a proposed partial Consent Decree for the Butte Priority Soils site.

BPSOU Resources

News & Updates

Design Investigation Along the Upper Silver Bow Creek Trail

Atlantic Richfield Company is conducting a design investigation along the upper Silver Bow Creek trail, adjacent to Harrison Avenue and the Butte Civic Center. The purpose of the investigation is to collect geotechnical data that will be used to support the design of...

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Summer 2024 Park Clean Up Notice of Temporary Closures

The Residential Metals Abatement Program (RMAP) will continue cleaning up parks and play areas throughout Butte during the summer of 2024. This work will result in temporary park closures. We thank you for your understanding and cooperation while we complete this...

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EPA Responses to Dr. John Ray’s Emails

On April 3, 2024, EPA posted responses to emails received from Dr. John Ray on February 20th and 29th, and March 1st and 6th, 2024. EPA compiled all emails and corresponding responses into one document and can be found here:...

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