Superfund Information Systems: Site Profile

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What Are the Risks at the Site?

All Superfund sites include an evaluation of potential threats to human health. This does not necessarily mean that exposures are occurring. While the community of Silverton is not included in the Superfund site, people do use the mining district for recreation. EPA collected data to evaluate possible exposures for a variety of recreational uses—ATV use, camping, hiking, guiding, fishing as well as traditional practices.

Mining operations have greatly disturbed the land, adding to existing highly mineralized conditions in many areas of the site. Mineralized waste rock exposed to air and water causes acidic conditions to mobilize the release of heavy metals to the surrounding environment. These heavy metals have found their way into the Animas River and its tributaries and have traveled farther downstream.

Evidence from the 2015 Draft Baseline Ecological Risk Assessment (BERA) indicates that:

  • The benthic invertebrate (small organisms that live in or on the bottom sediments of rivers and streams) community is impaired in most sections of the Animas River, Cement Creek and Mineral Creek. Effects are less severe further down the Animas River but are apparent to Bakers Bridge.
  • Water in the Animas River from Arrastra Creek to approximately Cement Creek is likely toxic to all trout species, with the exception of brook trout. Brook trout living in this reach, however, are likely stressed much of the year.
  • Metals concentrations in the Animas River below Mineral Creek have eliminated virtually all fish down to Elk Creek and all cutthroat and rainbow trout down to Cascade Creek, where only a small community of brook and brown trout exists. Results also predict fish populations are likely impaired down to at least Bakers Bridge.
  • It is unlikely that birdlife or mammal populations are experiencing significant negative effects from metals in the Animas River.

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Contaminant Information

View a full list of contaminants of concern for this site.

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Performance Measures

EPA uses performance measures to track environmental results at Superfund sites. If you have any questions or concerns about the measures at this site, please contact the site team members listed under Site Contacts.

Read more about Superfund Remedial Performance Measures.

Status at this
Superfund Site
What does this mean?
Human Exposure Under Control No Yes means assessments indicate that across the entire site:
  1. There are currently no unacceptable human exposure pathways; and
  2. EPA has determined the site is under control for human exposure.

No means an unsafe level of contamination has been detected at the site and a reasonable expectation exists that people could be exposed.

Insufficient data means that, due to uncertainty regarding exposures, one cannot draw conclusions as to whether human exposures are controlled, typically because:
  1. Response to the contamination has not begun; or
  2. The response has begun, but it has not yet generated information sufficiently reliable to evaluate whether there are currently any unacceptable human exposure pathways at the site.
Groundwater Migration Under Control No

Yes means EPA reviewed all information on known and reasonably expected groundwater contamination. EPA concluded the migration of contaminated groundwater is stabilized and there is no unacceptable discharge to surface water. EPA will conduct monitoring to confirm that affected groundwater remains in the original area of contamination.

No means EPA has reviewed all information on known and reasonably expected groundwater contamination, and the migration of contaminated groundwater is not stabilized.

Insufficient data means that due to uncertainty regarding contaminated groundwater migration, EPA cannot draw conclusions as to whether the migration of contaminated groundwater is stabilized.

Construction Complete No

Yes means the physical construction of the cleanup is complete for the entire site.

No means either physical construction is not complete or actions are still needed to address contamination.

Sitewide Ready for Anticipated Use No Yes means:
  1. All cleanup goals affecting current and reasonably anticipated future land uses of the entire site have been achieved, so there are no unacceptable risks;
  2. All required land-use restrictions or other controls have been put in place; and
  3. The site has achieved Construction Complete status.

No means that one or more of these three criteria have not been met. However, a site listed as no may still have redevelopment occurring on portions of the site and may be eligible for additional redevelopment.

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