OSWER/OSRTI

Washington, DC 20460

NATIONAL PRIORITIES LIST (NPL)

[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.

***Final Site*** March 2011

ACM SMELTER AND REFINERY Cascade County, Montana

Cascade County

 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 limited 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 a portion of the site.

 Site Contamination/Contaminants:

The plant stack was designed to emit 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, after which 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 runoff. These wastes are widespread and 

have been identified in the river at Fort 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:

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.