Casino Project: Interactive Design of A Large Tailings Dam to Achieve Mine Waste Management Objectives

Author: Sanne Brinkman, Graham Greenaway, P.Eng.
Conference: CDA Annual Conference 2014
Date: October 4-9, 2014

The Casino Project is a proposed copper-gold-molybdenum mine in the southwest Yukon. The deposit will be mined using open pit methods with a nominal mill throughput of approximately 125,000 tonnes per day of ore over a 22 year operating life. The climate at the project site is characterised by long, cold, dry winters and short, warm, wet summers. Permafrost is discontinuous over the Tailings Management Facility embankment area.

A waste and water management plan has been developed that considers geotechnical and geochemical characteristics of the various waste materials produced over the operating life of the mine. Waste rock and tailings will be selectively placed to provide subaqueous disposal of potentially acid generating materials, mitigate metal leaching potential and ensure long-term water quality and geotechnical performance objectives are achieved. The waste management strategy and dam design are being optimised during successive design stages as a better understanding of the geotechnical conditions and geochemical characteristics of the waste materials is obtained. The mine waste materials will be placed in a valley impoundment and constrained by a zoned embankment dam. The embankment will be constructed in stages using the centreline method, reaching a maximum height of over 280 metres at the end of mining operations. Mine tailings will be de-pyritized and cycloned to provide suitable sand fill for construction of the embankment shell zones. Design considerations include integration of the mine production schedule with construction of the Tailings Management Facility embankment and placement of waste rock, the impact of the cold climate on dam construction and facility operations, the impact of discontinuous permafrost foundation conditions on dam stability and integrity, and the effect of high confining stresses on the strength and permeability characteristics of the embankment construction materials.