Superfund Information Systems: Site Profile

Superfund Site:

NELSON TUNNEL/COMMODORE WASTE ROCK
Creede, CO

Cleanup Activities

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Background

The Nelson Tunnel/Commodore Waste Rock Pile Superfund site is located about one mile north of Creede, Mineral County, Colorado. At the abandoned hard rock mine site, the Nelson Tunnel discharges acid mine drainage directly into West Willow Creek. The site also includes a formerly unstable waste rock pile that is part of the Commodore Mine. These features contribute contaminants to surface water.

South of the site, West Willow Creek joins East Willow Creek to form Willow Creek. Willow Creek is a tributary of the Rio Grande River, a state-designated Gold Medal fishery. Historically, mining of silver, lead, and zinc provided economic benefits to the area in and around the Creede mining district.

Site Map (PDF) (1 pg, 3 MB, About PDF)

The site was added to the National Priorities List (Superfund) in September 2008. In 2008 and 2009, EPA conducted a removal action to stabilize the Commodore Rock Pile.

In 2011, EPA completed the site’s remedial investigation, which assessed the nature and extent of contamination. The site’s feasibility study is underway. The study will explore appropriate cleanup options.

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What Is Being Done to Clean Up the Site?

In 2008 and 2009, EPA conduced a Removal Action to stabilize the Commodore Rock Pile and reduce contamination entering West Willow Creek.

Health risk to people is through ingesting waste rock, soil or surface water, or by inhaling contaminated dust. In the short term, exposure pathways that could result in unacceptable risks are being controlled by restricting site access.

Investigations to support the feasibility study have been ongoing to determine an appropriate remedy for the Nelson Tunnel drainage. The Nelson Tunnel discharge is not a drinking water source.

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What Is the Current Site Status?

In 2011, EPA completed the site’s remedial investigation, which assessed the nature and extent of contamination. The site’s feasibility study is underway. The study will explore appropriate cleanup options.

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EPA’s Involvement at the Site

Surrounding Nelson Tunnel is the waste rock pile from the Commodore Mine, which is composed of waste rock from hard rock mining that accumulated over the mining years. The waste rock contains elevated levels of arsenic, cadmium, lead, manganese and zinc. In 2005, a high water event caused catastrophic failure of the pile. As a result, the Commodore Waste Rock Pile became highly unstable and partially collapsed into West Willow Creek.

In 2008 and 2009, EPA conducted a Removal Action to stabilize the Commodore Waste Rock Pile and to address immediate threats to human health and the environment. The Removal Action included reconfiguration of the waste pile and establishing a new channel for West Willow Creek. The pile was re-graded to create stable slopes that allow rain water and snow melt to flow toward the creek. The creek channel includes energy-dissipating structures to slow water flow through this steep canyon. Rock armoring of the channel protects the stability of waste rock pile by preventing the creek flow from undercutting the pile.

Characterization of the watershed identified the Nelson Tunnel adit drainage as the largest source of cadmium, lead and zinc in the Willow Creek watershed. West Willow Creek runs through the site carrying contamination into Willow Creek and the Rio Grande River which is four miles below the site. In 2011, EPA completed the site’s remedial investigation, which assessed the nature and extent of contamination. The site’s feasibility study is underway. The following activities have been conducted to explore appropriate cleanup options for the Nelson Tunnel.

  • Hydro-geologic investigations were conducted to determine if a hydraulic control remedy could mitigate the discharge from the Nelson Tunnel. This included the following:
    • An isotope analysis of water in the tunnel and other groundwater wells to understand the age, source and movement of groundwater in the area. This indicated that the water entering the Nelson Tunnel workings is largely old groundwater with only a smaller component of infiltrating precipitation water.
    • A detailed geologic investigation to evaluate the faults and fractures that may serve as a conduit for water entering the mine workings. The objective was to determine if drilling a deep well up-gradient of the Nelson Tunnel and Commodore Mine workings may allow water to be pumped before it becomes contaminated in the mineralized mine workings. The ability to accurately intersect clean water at a very deep location in this area has significant uncertainty and very high cost, therefore attempting to install a deep well has been determined to not be cost effective.
  • A mining company has explored reopening the nearby Bulldog Mine. Historical information indicates that when the Bulldog Mine was dewatered and operating in the 1980’s, the water flowrate from the Nelson Tunnel was reduced by an order of magnitude. If the Bulldog Mine were to reopen, it is anticipated that future remedy options would be significantly different because of the lower rate of Nelson Tunnel discharge.
  • Seasonal (quarterly) sampling of surface water in the Willow Creek watershed. Sampling objectives have included:
    • Identifying the impact of the Nelson Tunnel and the Commodore Waste Rock pile compared to other loading sources outside of the Superfund boundary,
    • Evaluating high and low flow (seasonal) water quality conditions in comparison to the State Water Quality Standards,
    • Obtaining baseline conditions to compare with conditions after a future remedy is completed.
  • Monitoring wells were installed in the fall of 2013 in the Commodore Waste Rock Pile, to investigate possible metal loading coming from the waste rock pile to the surface water. Another well was installed near the confluence of East and West Willow Creeks to distinguish downstream conditions. These locations are sampled quarterly along with the surface water sampling.

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Sampling and Monitoring

EPA is conducting seasonal (quarterly) sampling of surface water in the Willow Creek watershed. Sampling objectives have included (1) identifying the impact of the Nelson Tunnel and the Commodore Waste Rock pile compared to other loading sources outside of the Superfund boundary, (2) evaluating high and low flow (seasonal) water quality conditions in comparison to the State Water Quality Standards, (3) obtaining baseline conditions to compare with conditions after a future remedy is completed.

Monitoring wells were installed in the fall of 2013 in the Commodore Waste Rock Pile, to investigate possible metal loading coming from the waste rock pile to the surface water. Another well was installed near the confluence of East and West Willow Creeks to distinguish downstream conditions. These locations are sampled quarterly along with the surface water sampling.

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Emergency Response and Removal

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