HECLA GREENS CREEK FILTERED TAILINGS DISPOSAL
Mary-Jane Piggott, Klohn Crippen Berger Ltd.; Aaron Marsh, Hecla Greens Creek Mining Company; Sturgis George, Hecla Mining Company; Margaret Smith, Klohn Crippen Berger
The Hecla Greens Creek polymetallic mine in Alaska has the longest serving surface filtered tailings disposal facility in the mining industry. Continued exploration success resulted in the Life of Mine (LOM) extending for ten years beyond the capacity of the existing tailings disposal facility. The three-year design effort and following four-year construction period expanded the tailings disposal facility to meet the longer LOM plan. This paper discusses major technical, commercial, and organizational challenges that were successfully addressed during the design and construction effort required to support uninterupted mining operations. The expansion was constructed adjacent to and within the active tailings disposal facility. The construction was sequenced such that the expansion could received tailings before construction completion. this sequencing required collaboration between the operations and project teams to manage logistical and physical separation between tailings storage areas and construction areas that could not be used for tailings disposal. Technical challenges of note included: imported material selection, procurement, geochemistry, and temporary storage; native material geochemistry, removal, and storage; variability of the foundation conditions; and planning for closure. Commercial and organizational challenges and opportunities included: contractual changes; use of the Engineer of Record for design and construction; management of the design modifications during construction; and coordination between the project management team and the operations team. The seven-year design and construction effort is a measurable success on many fronts. Integrating multiple contractors into the mine’s safety culture resulted in permanent improvement in contractor safety performance. Tailings were placed as planned two years before the facility was complete. The cost and schedule were both within the approved project criteria. The principal project participants are currently engaged in the planning for the next tailings expansion with goals of replicating the successes and of carrying forward those items identified lessons-learned as discussed in this paper.
filtered tailings; design; construction; operations