Abstract
In the mine backfill industry, the typical replacement ratio, a number that measures the ratio between the mass of the ore mined and the mass of tailings placed underground, is approximately 50%. In other words, approximately half of the tailings cannot be returned underground. The remainder of the tailings not returned underground are most commonly stored on the surface within a tailings management facility (TMF). NexGen Energy has proposed an innovative solution for its Rook I Project (the “Project”) which would enable placing 100% of the process waste solids underground. Through constructing purpose-built underground chambers, the replacement ratio can be further increased beyond the traditional limits. This method also requires designing a backfill system that can reliably handle all streams of waste solids from the process plant regardless of the particle size and mineralogy. Utilizing a systematic set of material experimentations and engineering studies, multiple paste backfill mixes have been designed in consideration of the geotechnical and geochemical requirements for supporting mining operations, ground stability and permanent storage. This paper discusses the considerations, the approach, and the lessons learned from advancing a Project with zero process waste on surface.