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The Minago Project, owned by Victory Nickel, is located in the north-central part of the Province of
Manitoba, Canada. The site is perennially flooded and is covered with peat (muskeg), which overlies a
variable thickness of hard and then soft clay underlain by dolomite bedrock. The site climate is characterised
by warm wet summers, and cold and dry winters.
The project, which is completed to the feasibility level design, will comprise of an open pit mine producing
nickel ore, frac sand, dolomite, granitic rock, and ultramafic waste rock. The leachates from the dolomite
and the granitic rock units are not expected to raise any environmental concerns with respect to acid rock
drainage and metal leaching (ard/ml). however, ultramafic units are considered as potentially acid
generating and metal leaching (PAG/ML). During initial studies of on-land disposal, three separate waste
rock dumps for the ultramafic, granite and dolomite waste rock were considered. The ultramafic waste rock
dump included a perimeter effluent collection system and post closure treatment in-perpetuity. This was not
acceptable to the company and as such a new approach was required.
The key objective of subsequent approach was to mitigate environmental risks related to the disposal of
PAG/ML ultramafic waste rock. To meet this objective, a tailings and waste rock management facility
(TWRMF) was developed to encapsulate the PAG/ML ultramafic waste rock with tailings in a single
repository using a novel concurrent disposal approach.
A review of published precedents for co-disposal of waste rock and tailings was carried out. Although a
number of studies including laboratory/field-scale tests have been described in the literature, the results of
the review confirmed a lack of direct precedent for efficient long-term co-disposal applicable to the Minago
site-specific conditions. The development of the TWRMF disposal scheme draws upon selected components
of precedents from the authors’ experience. It is supported by analyses required to confirm technical
feasibility. There will be an emphasis on optimisation during detailed design and operational planning.
Mitigation of environmental risks will be achieved by minimising ARD/ML potential by partially submerging
the waste rock during operation, ultimately achieving full submergence of a combined waste rock and
tailings mass, and controlling seepage to tolerable limits in the long-term. Field trials and a comprehensive
instrumentation and monitoring program are planned. This paper focuses mainly on the environmental
issues involved and the selected disposal scheme.
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