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Closing the Buckhorn Mine

Crown/Kinross has indicated that the Buckhorn Mine will operate through 2016, closing active mining operations at the end of this year. The closure of the mine is a planned event; it is well established in the pre-mining planning documents that the mine was only anticipated to engage in active mining operations for 7.5 years.  Even so, Crown/Kinross and the Department of Ecology (Ecology) are struggling to keep the closure on schedule and ensure that the closure and reclamation of the mine site are conducted in a way that returns the site to its pre-mining condition.

After mining is complete, a mine reclamation phase begins. It will involve re-grading of the mine site, removal of the mine facilities, and re-vegetation, followed by two-years of post-reclamation monitoring. Hydrologic reclamation will continue until water quality is maintained at pre-mining levels for ten years. Reclamation of the Buckhorn Mine is complicated by various factors, one being that the treatment plant, which may have to operate for many years, cannot be removed at the end of mining. This is troubling because the treatment facility is thought to be built on contaminated construction fill, which must be removed because it is leaching contaminants into ground and surface water. This perplexing dichotomy has yet to be addressed.

The mine facilities are thought to be built on top of contaminated construction fill, which complicates reclamation. The fill must be removed because it is leaching contaminants into ground and surface water. However, the treatment facilities will be needed in order to treat the water in the years to come.

Another factor not anticipated in the planning process is that the mine has been unable to contain and control mine contamination to within the permitted boundary. Reclamation of the hydrologic system will likely be arduous and time consuming.

During the mine planning period, closure was expressed as the period of time from the end of reclamation until the water treatment system is no longer required. The time estimated for the closure period was thought to be comparable with the time it would take for the Gold Bowl section of the mine workings to flood. At this point, it is not clear how long the treatment system will have to operate, to bring the water quality back to what it was before mining, but it could be for a very long time.

Water quality and groundwater levels will be used to define the post-closure period; as a result, the actual timeframe for this period is fluid. At some point, the water level in the mine will reach equilibrium. Long-term water quality may be affected by seepage of poor-quality water from the Damaged Rock Zone located above the water table once the hydrologic system has reached equilibrium. The planning documents indicate that Ecology wants a 10-year monitoring period to see any water quality impacts in down-gradient groundwater monitoring wells.
The National Pollution Discharge Elimination System (NPDES) permit requires various mine-related plans be updated to reflect current conditions and also sets forth a framework and timeline for the reclamation plan.  According to the permit, 90 days before closure, Crown/Kinross is required to submit a mine closure plan. To ensure agency input, 30 days prior to the submittal of the mine closure plan, the permit requires a scoping meeting take place. This meeting allows Ecology to provide comments on what specific components should be included in the plan, and would have started the process on August 1st. Despite the company’s statement that the mine will close at the end of this year, this four-month process was not promptly initiated, and many of the mine’s NPDES-required plans have not been updated.