Region 8

Gilt Edge Mine

entrance sign
Entrance sign of the Gilt Edge mine site
Gilt Edge Mine site location map Site Type: Final NPL
City: Lead
County: Lawrence
Street Address: 4 miles SE of Lead
Zip Code: 57754
EPA ID: SDD987673985
SSID: 087T
Site Aliases: Brohm Mining Corp.
Congressional District: At Large

What's New?

Updated July 2012

The second five-year review for the Gilt Edge Mine is complete. The report is available in Site Documents below.

The Ruby Gulch Repository is associated with Operable Unit 3 at the Gilt Edge Mine Superfund Site. Surface water diversion ditches transport water around and away from the repository and reduce infiltration and subsequent acid rock drainage. EPA, in consultation with the South Dakota Department of Environment and Natural Resources (DENR), decided to minimize the leakage from the drainage diversion ditches by drilling and pressure grouting the stretches which have been shown to be highly fractured and leaking surface water into the ground.

ARRA logo

In 2009, the Gilt Edge site received $3.5 million in American Recovery and Reinvestment Act (ARRA) funds to implement the ditch grouting and lining work. In 2009, approximately 1,000 linear feet of the ditches were cleaned of rock, riprap, and other loose debris, drilled to an average depth of 20 feet, and pressure grouted which involves injecting concrete to seal joints, cracks and fractures. In 2010 and 2011, drilling and pressure grouting continued and some ditches were also lined with an impermeable geomembrane to aid in reducing infiltration. Approximately 3,200 linear feet of ditch were grouted and approximately 660 linear feet of ditch were lined with geomembrane to reduce or eliminate surface water infiltration into the Ruby Repository. These activities are anticipated to reduce the potential for mobilization of residual heavy metal constituents from the waste rock to surface water.

EPA is currently offering a Technical Assistance Grant (TAG), which it hopes to award to an interested community group. A TAG provides money for activities that help the community participate in decision making at eligible Superfund sites. Grant recipients can contract with independent technical advisors to interpret technical information about the site. For more information, contact Robin Coursen, Technical Assistance Grant representative.

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Site Description

The site is located about 6.5 miles east of Lead at the headwaters of the cold-water fisheries and municipal water supplies of the northern Black Hills in South Dakota. The 360-acre primary mine disturbance area encompasses a former open pit and a cyanide heap-leach gold mine. In the late 1990s the mine operator, Brohm Mining Company (BMC), became insolvent. In doing so, they left 150 million gallons of acidic heavy-metal-laden water in three open pits, as well as millions of cubic yards of acid-generating waste rock that requires clean up and long-term treatment.

Mining operations for gold, copper and tungsten were conducted in this small mining district starting in 1876. About a century ago, a series of small mines began dumping metals-laden mill tailing into Strawberry Creek and Bear Butte Creeks. By 1986, when BMC began conducting larger-scale open-pit mining, off-site waters were already contaminated.

When BMC faced financial problems and informed the State that it could not continue site controls, the governor of South Dakota requested that EPA Region 8 propose the site for the Superfund National Priorities List (NPL). EPA proposed the site on May 11, 2000 and announced the site's final NPL designation in the Federal Register on December 1, 2000. The NPL is a list of sites with environmental contamination, commonly referred to as Superfund sites.

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Site Risk

Sulfide waste rock and exposed ore zones (which generate leachates to surface and ground water) contain heavy metals, including arsenic, cadmium, chromium, copper, lead, nickel, silver and zinc. Elevated nitrates and sulfates are also present in heap leach residues. Copper, cadmium and zinc appear to be the metals contaminating the habitats of Strawberry and Bear Butte Creeks. While controlled through the use of a water treatment plant, the site presents no immediate threat to human health. If left uncontrolled, the large volumes of contaminated waters could threaten the well-water supplies of downstream users, including the city of Sturgis.

Media Affected Contaminants Source of Contamination
surface water, liquid waste, leachate, solid waste arsenic, cadmium, chromium, copper, lead, nickel, silver, zinc, nitrates, and sulfates mining activities and associated heap leach

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Cleanup Progress

The site is divided into three Operable Units: OU1, OU2 and OU3. In 2001, EPA developed interim cleanup plans for OU2 and OU3. Cleanup plans for OU1 were also developed and are presented in the Record of Decision for OU1, signed in September 2008. Public input was incorporated into all of the site cleanup plans.

OU1 addresses the surface contamination for the entire 258 acres of the site. EPA finalized the final Remedial Investigation (RI) report for OU1 in early 2008. The RI report details the nature and extent of the residual mining contamination in the groundwater, surface water, waste rock, and soils at the site.

EPA issued a Feasibility Study (FS) report in the spring of 2008. The FS report analyzed various remedial alternatives that could be used to reduce the amount of acid rock drainage that is generated at the site and to remove or contain contaminated fill materials. The primary objective of all of the alternatives described in the FS report, including the alternative ultimately selected in the ROD, was to reduce the amount of acid rock drainage that is generated on site in order to protect human health and the environment.

EPA issued a proposed plan for public comment in the spring of 2008. This proposed plan presented all of the alternatives offered in the FS and described in detail EPA's preferred alternative. In September 2008, EPA issued a ROD for the OU1 at the site, identifying EPA's final cleanup decision.

A primary goal of the OU1 cleanup will be to clean up and contain mine wastes at the site. This will reduce the amount of contaminated water that is generated on the site and treated in the water treatment plant.

OU2 includes the management and treatment of the acid rock drainage that threatens surface water in the area. Discharge of acid rock drainage water without treatment poses a risk to human health and the environment, particularly to surface water quality in Strawberry Creek and Bear Butte Creek. In 2001, after receiving public input on its plans, EPA implemented an interim remedy for OU2 that converted the existing water treatment plant to a lime, high-density sludge system. This provided a cheaper and more efficient means of treating the water onsite. The water treatment plant continuously treats acid rock drainage water that is collected at various facilities around the site. As of July 2007, there were approximately 180 million gallons of acid rock drainage water in storage. Several water diversion structures have been constructed to keep uncontaminated water from entering the treatment plant conveyance system.

The final remedial decision for OU2 will provide for the study, design, and implementation of a water treatment system that produces water in compliance with water quality standards. EPA will issue the final decision, taking public input into consideration, after the OU1 Record of Decision is implemented, and the resulting new site conditions are investigated. It is estimated that once the OU1 remedy is implemented, there will be less water onsite to treat, and the chemistry of this water will be different than the current conditions.

OU3 addresses acid rock drainage coming from the Ruby Gulch Waste Rock Repository. The Ruby Gulch Waste Rock Repository is a large acid rock drainage source on the Gilt Edge Mine site. Acid rock drainage generated from the sulfide-bearing wastes within the dump, if not reduced and contained, posed a major threat of contamination and release into the Ruby Gulch drainage and Bear Butte Creek. Beginning in 2001, EPA addressed this threat by reducing the volume of contaminated materials exposed, reducing water infiltration that produced large quantities of acid rock drainage, and containing waste materials. EPA constructed a cap for the Ruby Gulch Waste Rock Repository, which included a monitoring system. drainage systems, a synthetic liner and a clean soil cover. At the completion of that work in 2003, EPA began ongoing performance monitoring and operations and maintenance activities at the site.

In 2004 it was noted that outflows from the “Ruby Toe” were higher than anticipated. Tests performed on the diversion ditches indicated that many of the diversion ditches were leaking. Efforts are currently underway to repair the leaking diversion ditches to further reduce run-on from entering the water treatment system.

The remedial action at OU3 will be completed when the final eight acres adjacent to the water treatment plant are capped. This will occur during implementation of the OU1 remedy.

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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.

The agency hosted public meetings and public comment periods to gather input on the proposed plans for cleanup for OU2 and OU3 in 2000 and 2001. EPA mailed a site update to community stakeholders in 2002 and continuously updates its website in order to provide information to the public.

In the spring of 2008, EPA issued the Remedial Investigation report for OU1. EPA announced the availability of this report in local newspapers, held meetings with individual stakeholders, and hosted site tours at this time.

In May 2008, EPA issued a proposed plan for cleanup for OU1 and mailed the plan to community members and agency representatives. EPA held a public comment period on the proposed plan and notified the public of its availability in local papers and in e-mails. EPA hosted a public meeting to take comments from the public on the plan, met with stakeholders to hear their views, and again hosted site tours. The final ROD for OU1 includes public comments received on the proposed plan and our responses to those comments.

In January 2012, EPA and DENR staff completed community interviews with residents and local officials of Lead, Deadwood, Sturgis and Spearfish to update the community involvement plan. The updated plan is available in Site Documents below.

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Reuse

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. We use 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.
meteorological tower
Meteorological tower recently erected at Gilt
Edge will help to confirm that the site is a
viable source of wind energy.

EPA and the DENR convened a number of public meetings in 2005 to gather input on the potential future use potential for the site. The final report summarizing these meetings and public comment received is called the Community Involvement Plan: Final Report Initial Review of Potential Future Land Reuse.

One option for reuse is locating 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.

EPA, in consultation with engineers from Department of Energy's National Renewable Energy Lab (NREL), is evaluating whether Gilt Edge Mine site could be reused as a location for generating renewable energy. Regional wind maps indicate that the wind resource is very good (class 6 or 7). That fact, coupled with the existing electrical transmission lines, makes Gilt Edge a promising candidate site for a commercial wind farm. NREL believes that such a project could generate 40 to 50 megawatts of power, providing enough energy to meet the electricity needs of 16,000 to 20,000 average South Dakota homes. In May of 2010, EPA and NREL erected a 55-meter meteorological tower at the site to measure wind speeds for 16 to 18 months in an effort to confirm that the wind resource is as good as the regional maps indicate.

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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.

Land use controls at the site will be used to minimize risks posed to human receptors from unaddressed contaminant sources and also to ensure that engineered elements of the remedy (such as covers) are not damaged. They will prevent the unacceptable uses of groundwater that pose human or ecological risk, limit residential and off-road motorized vehicle rider uses, and allow only low intensity recreational site users and commercial workers. The land use controls will consist of a combination of both institutional controls (which may include community awareness programs and land-use restrictions) and engineered controls (which may include posted warnings and fencing).

ICs will be developed during the remedial action phase to address risks posed to human receptors from unaddressed contaminant sources.

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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 second five-year review for Gilt Edge Mine was completed in June 2012. The report is available in Site Documents below.

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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.Note: the larger documents below are located on the publicly accessible Gilt Edge FTP site. Best way to open a very large file: right-click and save it to a folder.

Please contact John Dalton for a copy of these documents.

Operable Unit 1

Community Involvement Plan, updated April 2012

Gilt Edge Mine Superfund Site Settlement With Property Owners, February 2011

Gilt Edge OU1 Record of Decision Volume I: Text, September 29, 2008

Gilt Edge OU1 Feasibility Study: Text, Tables and Figures (PDF), May 2008 (216 pp, 30 MB)

Gilt Edge OU1 Feasibility Study: Appendix A-H, May 2008 (PDF, 387 pp, 7MB)

Remedial Investigation Report, February 1, 2008

Remedial Investigation Report: Figures and Tables (PDF), February 1, 2008 (371 pp, 120 MB)

Gilt Edge OU1 Remedial Investigation Fact Sheet, February 2008

Community Involvement Plan: Initial Review of Potential Future Land Reuse, April 29, 2005

Baseline Ecological and Human Health Risk Assessments, November 2003

Operable Unit 2

Five-Year Review Report for Operable Units 2 and 3, June 2012

Update to the Five-Year Review – OUs 2 and 3, December 2010

Lime-HDS Water Treatment Plant Construction, February 2002–September 2003

Gilt Edge OU2 Interim Record of Decision, November 2001

Gilt Edge OU2 Early Action Interim Record of Decision, April 2001

Operable Unit 3

Five-Year Review Report for Operable Units 2 and 3, June 2012

Update to the Five-Year Review – OUs 2 and 3, December 2010

Ruby Gulch Waste-Rock Repository Construction, July 2001–June 2003

Gilt Edge OU3 Interim Record of Decision (PDF), August 30, 2001 (67 pp, 860 K)

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Contacts

EPA

Joy Jenkins
Remedial Project Manager
U.S. Environmental Protection Agency, Region 8
1595 Wynkoop Street (EPR-SR)
Denver, CO 80202-1129
303-312-6873
jenkins.joy@epa.gov

John Dalton
Community Involvement Coordinator
U.S. Environmental Protection Agency, Region 8
1595 Wynkoop Street (OC)
Denver, CO 80202-1129
303-312-6633
800-227-8917 ext. 312-6633 (toll free Region 8 only)
dalton.john@epa.gov

Robin Coursen
Technical Assistance Grant Representative
U.S. Environmental Protection Agency, Region 8
1595 Wynkoop Street (EPR-SR)
Denver, CO 80202-1129
303-312-6695
800-227-8917 ext. 312-6695 (toll free Region 8 only)
coursen.robin@epa.gov

DENR

Mark Lawrensen
Groundwater Quality Program
South Dakota Department of Environment and
Natural Resources
Joe Foss Building
523 East Capitol
Pierre, SD 57501-3181
605-773-3296
mark.lawrensen@.state.sd.us

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Photo/Video Gallery

Click on a thumbnail below to view the full size image.

Aerial view of the Gilt Edge Mine site
Dakota Maid Pit at the Gilt Edge Mine site
Dakota Maid Pit at the Gilt Edge Mine site
Sludge pond at the Gilt Edge Mine site
Water treatment plant at the Gilt Edge Mine site

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Links

Gilt Edge Mine Site at the South Dakota Department of Environment & Natural Resources Exit

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