Region 8

Upper Tenmile Creek Mining Area

Upper Tenmile Creek Mining Area site location map Site Type: Final NPL
City: Near Helena
County: Lewis and Clark
Street Address: Rimini Road
ZIP Code: 59601
EPA ID: MTSFN7578012
SSID: 081Y
Congressional District: At Large

What's New?

Updated July 2014

  • Efforts over the winter months were made to have all re-vegetation matters associated with the Lee Mountain Staging Area completed.
  • In the spring of 2014, EPA completed a government-agency-to-government-agency transfer of ownership of the 48,000-gallon former Community Wastewater Treatment Tank located on U.S. Forest Service managed property just North of Rimini. Currently, Baxendale Fire Department is pursuing a Special Use Permit from the Forest Service to utilize the tank and property.
  • Prioritized construction plans were established for 2014 and 2015: the National Extension mine waste site (south/southeast of Chessman Reservoir) and Bunker Hill mine waste site group (south of Rimini) are to undergo remediation and reclamation. This work will be in a phased approach with logging and grubbing, construction of temporary haul roads (as necessary) and stockpile areas as well as stockpiling of mine waste being conducted in 2014. The primary effort in 2015 will be the transport of excavated/stockpiled mine waste to Luttrell Repository. Note: the majority of truck traffic and heavy equipment operation will be outside of the Rimini community.
  • Remediation of a residential property located in the Landmark Subdivision will be conducted in 2014 with the removal and transport of contaminated material slated for 2015.
  • Reclamation of areas located near Luttrell Repository and the Basin Creek Mine are scheduled.
  • Source Adit Control/Acid Mine Drainage investigations will be conducted to support Remedial Design from the Red Water Mine discharge to the Susie Mine discharge.

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Site Description

The Upper Tenmile Creek Mining Area site is located in the Rimini Mining District, southwest of Helena, Montana. It consists of numerous abandoned and inactive hard-rock mine sites that produced gold, lead, zinc and copper. Mining began in the district before 1870 and continued through the 1920s. Little mining has been performed there since the early 1930s.

EPA added the Upper Tenmile Creek Mining Area to the Superfund National Priorities List on October 22, 1999, due to mining waste problems in the 53-square-mile watershed. The small historic mining community of Rimini is located within the Superfund site boundaries.

The site includes the drainage basin of Tenmile Creek upstream of the Helena water treatment plant and includes tributaries that supply water to the plant's five intake pipelines. EPA identified 150 individual mine sites within the watershed boundary, of which 70 have been prioritized for cleanup. Many of these mine features are above the five City of Helena drinking water intakes, which supply about 50 percent of the city's water.

The watershed has many stakeholders, including landowners, local communities, local and state government, special interest groups and several federal agencies, including EPA. Collaboration among the stakeholders is necessary to achieve a cleanup that will be expedient, efficient and long-lasting.

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Site Risk

Media Affected Contaminants Source of Contamination
groundwater, stream, soils arsenic, cadmium, copper, lead, zinc historic mining activities

Contaminants of concern are heavy metals, primarily arsenic, cadmium, copper, lead and zinc. Arsenic, cadmium and lead pose risk to human health while copper and zinc are toxic to fish.

EPA staff is coordinating with other state and federal agencies by addressing Clean Water Act problems related to mining wastes in the watershed that have been identified by the state. Tenmile Creek is the state's top priority for a Total Maximum Daily Load (TMDL) allocation.

EPA focused the Upper Tenmile risk assessments on development of risk-based preliminary remediation goals (PRGs) for the entire site. These are chemical-specific concentrations for various media, such as groundwater, that are protective for human health and the environment. Potential exposures to contaminants of concern in soil, groundwater, surface water, sediment, interior dust, airborne particulates and fish were evaluated. Based on land uses at the time of the risk assessment and potential future land uses as determined by observed trends and consultation with Lewis and Clark county officials, EPA considered the primary populations of concern to be residents, recreational visitors and workers.

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Cleanup Progress

The Upper Tenmile site is being cleaned up using a collaborative, watershed approach. To date, EPA has been unable to identify a potentially responsible party, so the cleanup on private land is being 90 percent paid for with federal funds and 10 percent with state funds. Cooperating agencies have combined resources to expedite a watershed cleanup. The U.S. Forest Service has taken the lead role in cleaning up wastes on federal property within the Superfund site boundary (Beatrice, Justice and Armstrong mines). Where individual mines involve both federal and private lands (Upper Valley Forge mine), cleanup expenses are shared by EPA and the Forest Service, with the State of Montana paying 10 percent. EPA and the Forest Service also share construction and maintenance costs of a joint mine-waste repository. Throughout the cleanup, EPA continues to work closely with the Forest Service, state and local community.

July 2014 – Luttrell Repository with temporary cover
2013 Response action at the Little-Lilly side of the Little-Lilly Lee Mountain Mining Complex

During the 2012 and 2013 construction seasons, significant progress was made at the Upper Tenmile site. Site progress over the past few years:

  • In 2012, 8,000 cubic yards of mine waste were excavated from primarily from the Lee Mountain portion of the Lee Mountain/Little-Lilly Mine Complex and all excavated mine waste material were transported to Luttrell Repository. Excavated areas were backfilled with appropriate select material and re-vegetation/reclamation conducted.
  • In 2013, 11,000 cubic yards of mine waste were excavated from the Little-Lilly portion of the Lee Mountain / Little-Lilly Mine Complex and all excavated mine waste material were transported to Luttrell Repository. Backfilling and re-vegetation/reclamation of the excavated material was conducted. Arsenic levels removed from this area ranged as high as 186,000 parts per million (ppm) which is significantly higher than the highest level range typically encountered on Superfund Sites, 70,000 – 100,000 ppm.
  • In addition, 1,000 cubic yards were excavated from the Lee Mountain Staging Area and the area was backfilled and reclamation began with final re-vegetation efforts being conducted in 2014.

During construction, every effort was made to facilitate the flow of truck traffic from the remediation sites to the repository, as well as coordinating large equipment working on the various projects. U.S. Forest Service roads were closed during the week and all traffic was controlled by flag personnel.

The total volume excavated and placed in Luttrell Repository from the Upper Tenmile Mining District Superfund Site to date is 354,000 cubic yards.

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Community Involvement

Community involvement plays an important role in the Superfund process. EPA uses a number of different tools and resources to promote effective, on-going, meaningful community involvement. The goals of the Superfund community involvement program are to:

  • Keep communities affected by sites informed throughout the cleanup process.
  • Provide opportunities for communities to comment and offer their input about site cleanup plans.
  • Facilitate the resolution of community issues tied to a site.

EPA's Superfund response action at the Upper Tenmile Creek Mining Area site has provided information via public meetings, the administrative record file for the site, and announcements published in local newspapers. EPA participates in monthly meetings of the Upper Tenmile Watershed Committee and routinely discusses the cleanup plans with area residents and property owners. These meetings are open to the public and often times have representation from the local residents.

In addition, during the field season, EPA distributes periodic construction updates via fact sheets and maintains a project office in Rimini, where residents are welcome to stop by with questions. Tours and briefings are offered to local officials.

Community participants representing Rimini Community, Inc. declined to continue the Technical Assistance Grant (TAG) in 2013. To date, approximately 87 percent of the residences identified as needing response action have completed remediation. Institutional Controls will need to be established, with cooperation of MDEQ and Lewis & Clark County, to address any of those properties which were not remediated due to legal/access issues.

EPA's Community Involvement Plan for the site is available in Site Documents below.

Should you have further Community Involvement needs, please contact Kathy Ericksen, Superfund Community Involvement Support for the EPA Montana Office.

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EPA places a high priority on land reuse as part of its Superfund response program mission. The agency tries to select cleanup options that encourage and support future use of a site. EPA uses two fundamental methods to facilitate reuse of Superfund sites:

  • Exploring future uses before the cleanup remedy is implemented, an approach that gives the agency the best chance of designing cleanup remedies to support the likely future use of a site.
  • Working with landowners and communities to remove barriers not considered necessary for the protection of human health or the environment at those sites where remedies are already in place.

One option for reuse is the siting of clean and renewable energy projects on contaminated (or formerly contaminated) lands. As part of this effort, EPA is evaluating the potential for energy projects on these properties and working with landowners and communities to identify ways to remove barriers to such projects.

Many properties in Rimini and in the Landmark Subdivision are already in continued use as residential properties.

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Land Use Controls and Other Institutional Controls

Land use controls are the most common type of institutional control (IC). ICs are administrative or legal controls that help reduce the likelihood for human exposure to contamination. ICs can also help protect the integrity of the remedy. Examples of ICs are:

  • Zoning ordinances.
  • Environmental covenants.
  • Deed notices.
  • Well-drilling restrictions.
  • Building permits.
  • Informational advisories.

EPA awaits availability of Lewis and Clark County representatives so as to address ICs, including discussions of a groundwater control area within the boundary of the Upper Tenmile Watershed.

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Five-Year Reviews

EPA or the lead agency conducts five-year reviews following the start of a Superfund cleanup when contamination is left on the site. These reviews are repeated every five years. We use these reviews to determine:

  • How the remedy is working.
  • If the remedy remains protective of human health and the environment.

The first five-year review of the Upper Tenmile site was completed in 2008; the report is available in Site Documents below or at the EPA office in Helena. The second five-year review was scheduled for completion in 2013 and is unavailable for posting at this time due to delays in the review process. The third five-year review will remain scheduled for 2018.

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Site Documents

You will need Adobe Reader to view some of the files on this page. See EPA’s About PDF page to learn more.

Best way to open a very large file: right-click and save it to a folder.

Update to the Five-Year Review, January 2011

First Five-Year Review Report (PDF), July 2008 (61 pp, 2.1 MB)

Amendment to the 2002 Record of Decision (PDF) (ROD Amendment), September 2008 (215 pp, 40 MB)
Note: if you cannot open the above file, go to the Upper Tenmile public FTP folder.

ROD Amendment Fact Sheet, September 2008

Community Involvement Plan, July 2008

EPA Cleanup Update July 31, 2008

EPA Cleanup Update September 30, 2007

Proposed Plan to Amend the 2002 Record of Decision (ROD), October 2007

Upper Tenmile Creek Mining Area Fact Sheet, January 2007

Record of Decision (PDF), June 28, 2002 (361 pp, 2 MB)

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Tillman McAdams
Remedial Project Manager (for OU1)
U.S. Environmental Protection Agency
Region 8, Montana Office
Federal Building
10 West 15th Street, Suite 3200
Helena, MT 59626
866-457-2690 (toll free)

Kathy Ericksen
Community Involvement Support
U.S. Environmental Protection Agency
Region 8, Montana Office
Federal Building
10 West 15th Street, Suite 3200
Helena, MT 59626
866-457-2690 (toll free)


Richard Sloan
Project Officer
Montana Department of Environmental Quality
1100 North Last Chance Gulch
P.O. Box 200901
Helena, MT 59620-0901
800-246-8198 (toll free in-state only)

Site Information Repository:

EPA Superfund Records Center
Montana Office
10 West 15th Street, Suite 3200
Helena, MT 59626
866-457-2690 (toll free)
Hours: M-F, 8:00 a.m.-4:30 p.m.

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Photo/Video Gallery

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The following links exit the site Exit

Montana Department of Environmental Quality, Remediation Division

Lewis and Clark County, Montana

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