Midnite Mine Superfund Site Moves Closer to Cleanup Design | Region 10 | US EPA

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Midnite Mine Superfund Site Moves Closer to Cleanup Design

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Design elements being discussed

Planning for the cleanup of Midnite Mine has been in the works for several years. Dawn and Newmont (the mining companies involved with Midnite Mine) have been gathering information and will submit a preliminary design to EPA by the end of the year.

Coming up with a detailed design for the cleanup is complicated. The design must factor in steep conditions, two deep open pits, and a lot of waste rock that must be moved. As waste rock is being placed into the pits, a process that will take years, the pits can no longer be used to store water. Since contaminated water must not leave the site, even during winter rains and spring snowmelt, the water must be stored and treated to meet permit limits, and waste from the water treatment process must be properly disposed.

This year, we have held a number of project meetings to work through challenges related to the design. These include questions about construction materials, how to phase the work, where construction materials, water storage, buildings, and equipment will be located, what safety and environmental controls will be needed during construction, and other related topics. The meetings were attended by EPA, the mining companies’ design team and Tribal experts, and they were open to the public.

No final decisions on the questions below have been made, and the design will go through several reviews, each time at a greater level of detail. The designers are beginning to piece together a preliminary design that EPA thinks will meet the cleanup goals, will protect workers, the environment, cultural resources, and the community during construction, is acceptable to the Tribe, and will be effective over the long-term. The preliminary design will be available for review in December.

Here is a summary of a few of the topics we’ve covered at these meetings.

Impacts to Workers and the Environment

  • What's the best way to protect workers from rockfall and slides when work is happening in the pits?
    • Work areas will be limited, and a safety berm at the base of the pit walls will be used to catch material and protect workers, but is it also necessary to "scale" the pit walls to remove loose material?
  • How will environmental impacts of the cleanup be avoided?
    • We are looking at ways to use local resources and workers, minimize trips (as examples: providing a bus for workers and keeping construction equipment on site), use efficient practices and low-sulfur diesel or biofuels where possible.

Construction Design

  • How can the design ensure that the cleanup is successful over the long-term?
    • The design must include construction quality control, backup systems, careful operation and maintenance, monitoring, and contingency plans.
  • What material should be used for the drain layer on the bottom of the open pits?
    • We need to use coarse material that won't break down or increase acid drainage over the long term.
  • How can we keep particles carried by rain and snowmelt from clogging the pit drain layer?
    • Can the pit walls be modified to direct water away from the drain layer?
  • What will the final covered area contours be?
    • The contours will depend on how much material goes into each pit and will be designed to prevent erosion and support revegetation.
  • What's the best layout for access and work areas during construction and over the long-term?
    • We are looking at placing a staging area on the west side of the site. An old road west of the mine may be upgraded for use during construction. This will allow contaminated mine access and haul roads to be cleaned up.

Construction Materials and Timing

  • Which waste rock pile will be moved into which pits?
    • We need to ensure that the material containing the most uranium is well below the surface, but that the material most likely to cause acid drainage is above where water could saturate it.
  • Which pit would be filled and covered first?
    • Pit 4, higher on the hill, would likely be filled first. Pit 3 could continue to store water while some areas are cleared of mine waste. This will reduce the amount of contaminated water that must be stored and treated.
  • Where will water be obtained to control dust during construction?
    • We are considering using water from the treatment system for dust control. If this is not an option, we would need to use off-site sources. Water rights are required for any source.
  • Where will material (dirt, soil, organic amendments) be obtained for pit covers after backfilling?
    • There are two primary options being considered: one next to the mine and one near Ford. The ID team is reviewing the mining company proposal. To help plants grow, organic material may have to be added to the soil. The Tribe recently suggested using organic material from three lakes on the reservation that are filling in with tule mats. Before dredging, further review of the benefits, impacts, costs, process and requirements would be needed.

Water Management, Treatment and Storage

  • As the open pits are filled, where will water be stored?
    • One pit can hold water while the other is being filled. Filling the second pit will take a few years, though, and water must be contained. A temporary pond could be built in an area where waste rock is to be removed.
  • Where will the new water treatment system be built?
    • A proposed location on the west side of the site is being discussed with the Tribe.
  • Can the water treatment system be modified to reduce the cost of managing the treatment sludge?
    • The water treatment system produces waste that must be taken to a radioactive waste facility. Changing the system to remove uranium first would produce much smaller volumes of radioactive waste. The rest of the waste would not be radioactive waste. Testing is being done to help with design of the modification.
  • What's the best way to remove water from the drain layer?
    • Sumps, pumps and vertical or angled wells will be designed to capture water in the sump, allow water levels to fluctuate within the sump only, and ensure that the wells will work during and after backfilling the pits.
  • How can we ensure that clean water stays clean and contaminated water is captured for treatment?
    • Moving waste and filling the pits will cause the landscape to change during construction. Surface water controls will be monitored and updated often.
  • How will treated water be discharged?
    • EPA plans to update the current permit to meet the Tribe’s water quality standards. This will follow the normal permit process, with public comment on a draft permit. Instead of discharging treated water on site, where it flows to Blue Creek, treated water will be piped to the Spokane River and discharged there.
    • The designers are considering an underground pipe to and along the Blue Creek road. The pipe would continue to the middle of the Spokane River channel, where the water is deepest. We are working with the Cultural Preservation and various agencies to best locate and design the pipe. The pipe design and installation must protect cultural resources and the environment, prevent erosion and boating hazards when the lake water level is low, and protect and monitor the pipe itself.

Some places for community input

We would like your input on certain topics that may affect the community. EPA and Newmont plan to display information about the preliminary design in November and will be available to answer questions and listen to your concerns or suggestions. Look for news about where the informational displays will be in the next Rawhide and posted announcements.

Here are some topics we’d like to hear from you on:

  • Are there times of year or times of day when construction at the site could be a problem for the community or the local environment?
  • Are there sections of road on the reservation where you have concerns about traffic safety? What routes, timing, lighting, speed limits, vehicle markings, etc, could address these concerns?
  • How should EPA inform and engage the community about site activities during the expected 7 to 10 year construction project on the reservation?
  • After construction, how can the community help prevent damage to the completed cleanup, which would expose contaminated materials?
  • What kinds of information and activities will help the community understand and have confidence in the cleanup? Site visits? Photos or videos on a website? Rawhide Facebook?
  • Some Blue Creek sediments may need cleanup too, once work is completed at the mine site. Are the new signs clear? Are people following the health recommendations given by ATSDR that were published in the Rawhide in the past?

EPA contacts

  • Project Manager - Elly Hale (hale.ellie@epa.gov), (206) 553-1215

Spokane Tribe contacts

  • Superfund Coordinator - Randy Connolly (connolly@spokanetribe.com), (509) 626-4425. Randy has been helping gather input from the Tribe--including the IRMP, Cultural Preservation, the Tribal Business Council and community members.
  • Director, Department of Natural Resources - BJ Kieffer (bjk@spokanetribe.com), (509) 626-4427

Mining Company Representative

  • Newmont Representative - Bill Lyle (bill.lyle@newmont.com)

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