May 18, 2018, North Bay, ON, Canada – Craig Hall, specialist geotechnical engineer based in Knight Piésold’s North Bay office, delivered a talk during the mine closure session of the Montana Tech Mine Design, Operations & Closure Conference. Montana Tech of the University of Montana hosted the conference, which celebrated its 26th year as the last educational conference of its kind in the northwest USA, on May 6-10, at the Fairmont Hot Springs Resort in Montana.

Craig provided conference attendees an overview of the proposed closure enhancement for the Nye Tailings Impoundment at the Stillwater Mine site with the presentation entitled “Tailings Impoundment Closure Enhancement.” The presentation focused on the characterization of low strength tailings within the impoundment, the anticipated behavior of the tailings as the tailings consolidate, capping of the impoundment with waste rock, and additional waste rock placement over the tailings impoundment closure cap.

The placement of additional waste rock over the tailings impoundment will promote further consolidation, densification, and dewatering of the tailings to achieve dense, non-flowable tailings. This will result in a low consequence dam safety classification for a hypothetical post-closure dam breach and allow additional waste rock to be integrated into the post-closure landform, which will reduce the need for additional site disturbance.