British Columbia Mine Reclamation Symposium

Managing for closure at the Myra Falls Operation : the design of a soil cover system for long term ecological and physical stability O'Kane, Mike; Mchaina, David Mhina; Stoicescu, Jeffrey; Januszewski, Steve; Haug, Moir D.; Bews, Brenda E.


Westmin's Myra Falls Operations has the one single largest environmental problem facing the mining industry today. The tailings and waste rock materials are acid generating. A review of existing literature indicates that there are a number of technologies that can be used and developed for the prevention and control of acid generation in sulphidic mine tailings and waste rock. The majority of the ARD control technologies are centered around the curtailment of oxygen and water to the waste material. The most promising technology for Westmin's Myra Falls Operations is engineered soil covers. An initial cover design evaluation using local till materials indicated that the materials were not suitable for the proposed application. However, the soils were modified with a selection of amendments and the laboratory results showed significant improvements. The results suggest that local till materials amended with either flyash or bentonite can be used in soil cover construction. Westmin intends to conduct field trials to evaluate the performance of a short list of soil cover variations to determine the final cover system design as a result of the encouraging laboratory and soil-atmosphere modelling results. This paper summarizes the results of the laboratory characterization of the potential cover and waste materials and presents the soil-atmosphere numerical modelling used to design the field test plots. Construction aspects, instrumentation, vegetation, two-dimensional flow and in general the scope of the project will be briefly discussed. The successful use of local till material ameliorated with a fine grained material will provide a positive impact to the mining industry. This application to the design of soil cover systems is a novel approach which offers an economic alternative for decommissioning smaller waste rock piles and tailings management facilities.

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