Superfund Site: EAGLE MINE, MINTURN, CO
Superfund Site Profile
The Site – A Short Description: The Eagle Mine Superfund site is located in the Rocky Mountains, approximately 8,000 feet above sea level, bordered to the south and west by the White River National Forest. The roughly 235 acre site sits one mile south of the town of Minturn in Eagle County, Colorado. The Eagle River and a number of its tributaries flow through the site, which is an area heavily impacted by heavy metal contamination as a result of past mining activities. The site includes an estimated 70 miles of underground mine tunnels; underground mill workings; the abandoned company town of Gilman; and various mine waste features such as former roaster pile areas; waste rock piles; tailings piles; a tailings slurry line and trestle, and the Belden Mill and load out area. Contaminants include of arsenic, cadmium, copper, lead and zinc in the soils, structures, surface water, sediments, and groundwater across the site.
EPA divided the Eagle Mine Superfund site into three Operable Units (OUs). Operable Unit 1 was established to control the transport of heavy metals from the principal sources of mine waste (such as the Eagle Mine itself and various tailings and roaster piles) that were impacting the Eagle River. OU2 was established to evaluate health risks at Maloit Park Wetlands, the Minturn Middle School and the abandoned company town of Gilman. Because the wetlands have been remediated and the school proved not to be a risk, OU2 today focuses on contaminated soils at Gilman only. OU3 (also referred to as the North Property) was established in the early 2000s to mirror the boundaries of a private residential development proposed for the area at that time.
The History – A Century of Mining: Miners began mining for gold and silver in the Battle Mountain area between the towns of Minturn and Red Cliff as early as the 1880s. In 1912, the Empire Zinc Company, later a subsidiary of New Jersey Zinc Company, began consolidating individual mining claims into what is now known as the Eagle Mine. In 1929, a mill was constructed underground within the mine workings and the tailings were slurried through a pipeline/trestle system to a location downstream, known as the Old Tailings Pile. In the mid-1940s, the Old Tailings Pile reached capacity. Tailings were then deposited across the Eagle River from the Old Tailings Pile in an area known as Rex Flats. In 1942, the pipeline was extended to a location near Cross Creek using an elevated wooden trestle to cross Rex Flats, and the New Tailings Pile (now known as the Consolidated Tailings Pile) was constructed. The New Tailings Pile also included a 1.5-acre water retention pond known as the Historic Pond. Tailings were again deposited in Rex Flats in the 1950s.
Did You Know? The Eagle Mine became one of the largest zinc mines in the United States, contributing significantly to the nation’s zinc supply during WWII. During its lifetime, the Eagle Mine produced more than 12 million tons of ore.
In December 1977, then-owner Gulf + Western Industries, Inc. closed the mill and most mining activities ceased. Some copper and silver production continued until the mine workings were allowed to flood and the mine closed in 1984. Remaining workers vacated the company town of Gilman immediately after the mine closed. Portions of the site were bought and sold numerous times in years that followed. EPA and the state of Colorado identified CBS Operations, Inc. (CBS) as the party responsible for the cleanup of the site. CBS had acquired Viacom International, Inc., the successor in interest to New Jersey Zinc Company.
TOPICS IN FOCUS
New Cleanup Effort for Operable Unit 1 – Sitewide Contamination: A new cleanup effort for sitewide contamination, referred to as Operable Unit 1 (OU1), is necessary because in 2009, the Colorado Water Quality Control Commission revised its water quality standards for the Eagle River as it flows through the Eagle Mine Superfund site. To comply, the transport of metals from various sources on the site to the Eagle River and to groundwater must be further reduced. (See more information in What is the current site status?)
New Cleanup Effort for Operable Unit 3 – The North Property: A new cleanup effort at a portion of the Eagle Mine Superfund site referred to as the North Property, or Operable Unit 3 (OU3), is necessary to allow a portion of the site to be reclassified for a potential residential future use. Cleanup efforts to date at the Eagle Mine Superfund site were not intended to allow for residential use of the property, which requires a more thorough cleanup scenario. EPA and the state are currently working with the property owner to make sure that all necessary investigation and cleanup steps occur to prepare the property for residential redevelopment. (See more information in Redevelopment Activity.)