On August 16, 2016, the Department of Ecology (Ecology) held a scoping meeting required by the Buckhorn Mine discharge permit for its reclamation and closure. The Department of Natural Resources is responsible for geologic/surface reclamation and Ecology will administer the hydrologic reclamation. The mining company presented an overview of the general categories that will be covered in the plan, but omitted specific details contained in their 2014 plan for reclamation water management. The company went so far as to define scoping as being limited to input on the general categories, and claimed that specific input on the details of the plan was not part of scoping. OHA had a much different approach, stating that the details are extremely important, and highlighted information from the company’s 2014 plan that was not part of the 2006 plan. Environmental review was conducted on the 2006 plan, but many aspects of Crown/Kinross 2014 plan – if approved by Ecology – could have significant unintended environmental consequences that have not been previously considered. OHA’s initial recommendations for reclamation and closure scoping include:
- The closure plan should include a strategy for bringing all ground and surface water inside and outside of the capture zone into permit compliance and maintaining it for ten years.
- The plan to add a hydraulic barrier between the Gold Bowl and Southwest zone workings should be examined in more detail, and should include an analysis of potential unintended consequences, including potential for a blowout and the creation of mine water seeps.
- Annual drawdown of the Gold Bowl zone will promote the formation of acid mine drainage and should be avoided.
- The lack of shotcreting* of ore headings and portions of the damaged rock zone (DRZ) should be taken into account when estimating the time for water to attain permit limits. Adding DRZ areas to the 3D visualization tool would help identify additional areas requiring shotcrete.
- The mine water treatment plant should continue operating until the entire mine site meets permit limits. A thorough characterization study of the construction fill under the treatment plant and surge pond should be conducted and submitted to Ecology. If the need for removal of the construction fill is demonstrated and the treatment facility is moved, the closure plan should show that comparable treatment capacity and effectiveness would be installed.
- The primary objective of the reclamation and closure plan should be to reach permit limits as soon as possible, rather than as soon as practicable.
- Discrepancies in the reclamation and closure plan, including, for example, inundation of the Gold Bowl zone and annual water level drawdown, need to be addressed and resolved in the water management reclamation and closure plan.
- The estimated time to meet permit limits should include predictions for sulfate, not only nitrate, and should consider seasonal maximum concentrations rather than only average values. Initial higher concentrations created by flushing sulfide oxidation products should also be evaluated in terms of treatment requirements and the time to attain permit limits.
- Material under the potentially acid generating rock liner should be tested for leaching potential, removal of the liner should be included as part of site reclamation, and measures needed to reduce leaching potential should be evaluated.
*Shotcrete is a sealing substance used to make a material “passive,” or less influenced by environmental factors such as water and air, to help prevent acid mine drainage.