OSWER/OSRTI 

Washington, DC 20460 

NATIONAL PRIORITIES LIST (NPL)

***Proposed Site*** March 2010 

ACM SMELTER AND REFINERY Cascade County, Montana 

 Site Location: 

The site is a former metals refinery adjacent to the unincorporated community of Black Eagle along the Missouri River 

in Cascade County, Montana. The City of Great Falls is located across the Missouri River from the site. 

 Site History: 

The Boston & Montana Consolidated Copper and Silver Mining Company began construction of the first smelter at 

the 427-acre metals refinery site in 1892. Primary products from activities at the site were copper, zinc, arsenic, and 

cadmium. Operations began in 1893 when ore from mines in Butte, Montana was concentrated, smelted, and refined. 

Electrolytic and furnace refineries also operated at the site. The property was acquired by Anaconda Copper Mining 

Company in 1910. Smelting and refining activities continued at the facility until the early 1970s. The property again 

changed hands in 1977 when these holdings were purchased by Atlantic Richfield Company (ARCo). The plant began 

closure in 1973. ARCo has conducted minor cleanup of the former facility, but the site has never been under an 

approved cleanup program with EPA or the state. A recycling facility and golf course currently remain on site. 

 Site Contamination/Contaminants: 

The plant stack was designed to eject lead, arsenic, and other metals in emissions. As a regular practice, tailings, 

smelter wastes, slag, and flue dust were dumped into the Missouri River until 1915, when most wastes were deposited 

on-site. The state estimated 27.5 to 31 million tons of slag and tailings were dumped directly into the River. 

Contaminants associated with these sources included antimony, arsenic, cadmium, chromium, cobalt, copper, iron, 

lead, manganese, mercury, nickel, selenium, silver, and zinc. 

 Potential Impacts on Surrounding Community/Environment: 

In 2007 and 2008, EPA soil studies of residential yards in Black Eagle found approximately 45% of the sampled yards 

had elevated levels of lead and/or arsenic. Stack deposition from the smelter between 1893 and 1972 is most likely 

responsible for yard contamination. Residents reported that some of their housing was constructed using materials 

from the Site. In 2004, the Missouri River was found to be contaminated from dumping and site run-off. These wastes 

are wide spread and have been identified in the River at Ft Benton, 34 miles downstream from the site. The Missouri 

River is a fishery for area residents. 

 Response Activities (to date): 

There have been no response activities to date. 

 Need for NPL Listing: 

ARCo has conducted minor cleanup at the site. Montana referred the site to EPA in 2002. More recently, Cascade 

County sent a letter to Montana expressing their support for listing. Other federal cleanup programs were evaluated, 

but are not viable because of the complexity of the site and the need for enforcement mechanisms. EPA received a 

letter of support for placing this site on the NPL from the Governor. 

[The description of the Site (release) is based on information available at the time the Site was evaluated with the HRS. The description may change 

as additional information is gathered on the sources and extent of contamination.] 

For more information about the hazardous substances identified in this narrative summary, including general information regarding the effects of exposure to these 

substances on human health, please see the Agency for Toxic Substances and Disease Registry (ATSDR) ToxFAQs. ATSDR ToxFAQs can be found on the Internet 

at http://www.atsdr.cdc.gov/toxfaq.html or by telephone at 1-888-42-ATSDR or 1-888-422-8737.