USE OF GRANULAR COVERS FOR TAILINGS IMPOUNDMENT CLOSURE

摘要

Homestake Canada Inc. has used granular covers for the tailings impoundment closure at its Nickel Plate and Snip Mines. The most recent being the Snip Mine in northwest British Columbia, which ceased operation in June 1999 and completed site reclamation by October 1999. This paper will review the design criteria, key issues and construction activities of the final impoundment configuration to ensure long term security of the tailings and steps taken to mitigate potential of ARD being generated. Although some of the tailings were classified as potentially acid generating during the early stages of operations, later tests indicated non-acid generating tailings. The Nickel Plate tailings impoundment cover consists of approximately 600 mm of random rockfill covered with 600 mm of till moderately compacted over the beached tailings surface. The Snip tailings impoundment cover consists of approximately 500 mm of random rock fill covered with 150 mm of topsoil. Saturation of the tailings is maintained by local runoff entering the tailings impoundment and the saturation level is maintained by a spillway at the interface between the tailings and the granular cover. Some leveling in the beach area of the tailings was needed to provide a very gently sloping tailings surface to promote runoff and to maintain the tailings in a. saturated condition. Extensive use of geo-textile was used, and was effective, to facilitate placement of the cover over wetter areas of the tailings impoundment. The paper discusses the design steps for the closure scenario including analysis for long term stability, the approval process, and construction activities to achieve a closure and reclamation even in weather limited construction period.