Capstone Resources Minto Mine

Since 2007, Capstone Resources Minto mine has made a number of modifications to deal with unanticipated extreme precipitation events and permafrost degradation Minto mine was planned in the early 1990’s when a changing climate was not a major consideration. Minto is the largest operating mine in the Yukon, and in 2013 will be the only one operating on a year round basis. Planned in the 1990’s and opened in 2007, the mine is located in the discontinuous permafrost zone 240 km north of Whitehorse close to the Yukon River in the Traditional Territory of the Selkirk First Nation. Initially it was expected that the Minto venture would yield 371 million pounds of copper over an anticipated life-span of eight years. The mine has expanded several times since inception, and recent discoveries are expected to extend mine life beyond 2020. Climate related problems including flooding and permafrost degradation have beset the mine ever since it opened, and the nature of these problems and the manner in which Capstone has responded illustrate both the way in which a changing climate is manifest and the challenges faced by a mine responding and adapting as problems arise. The Selkirk First Nation, located down-stream from the mine has a strong vested interest in the maintenance of the region’s environmental integrity and is a major player in ensuring that negative externalities from the mine-site are minimized.

Understanding and Assessing Impacts

Rainfall and run-off events in 2008 and 2009 forced the company to ask for amendments to its water license to release untreated water into the Yukon River system. In 2008 heavy rains resulted in flooding and the mine’s water treatment plant was overwhelmed resulting in the release of some 350,000 cubic meters of untreated water into the Yukon River, and the effluent content (.05 mg per litre) was higher than Yukon license standard of .01 mg per litre. Ironically the water storage pond had been designed to assure water availability throughout the year, given an expectation of occasional seasonal summer drought. The 2008 rainfall also washed out a four kilometre section of the mine haul road to Minto Landing, linking into the Klondike Highway. In 2009 the problem of excess water on the mine-site, this time attributed to unusually heavy spring melt, was exacerbated because the wall of as storage pit was partially collapsing because of permafrost melt, and 750000 CM of water were discharged into the Yukon River system.

Identifying Actions

There is considerable evidence that the water management issue reflects failure to realistically consider climate trends during mine design, and following the floods of 2008\2009 Capstone’s management acknowledged that climate projections when the mine was designed failed to accommodate the possibility of climate change. Following the flood the company gave some consideration to allowing water to accumulate on the mine-site and processing and releasing it in timed stages. However it was recognised that this would have compounded the problem because winter snowfall and spring freshets would merely add to the water volume and consequently Minto made releases into the Yukon system in excess of levels specified in its water license. Longer term responses included digging ditches to manage on site water, development a of a new water management plan based on more recent hydrological data, and in 2010, construction of a new water treatment plant designed to treat 4000 cubic meters of water a day. Movement of the dry-stack is acknowledged to be a problem. Dry-stack storage was designed to solve one climate induced problem but resulted in another, and while this response could perhaps be viewed as maladaptive it’s illustrative of the capacity of a changing climate to translate into multiple stressors and the difficulty of identifying appropriate responses. The initial response is to monitor the situation and build an abutment to try and stabilize the stack. In the longer term the company is working jointly with the Selkirk First Nation to develop a strategy for addressing the issue.


Capstone purchased the Minto Mine from Sherwood Resources in 2007, and has made a number of modifications to deal with unanticipated extreme precipitation events and permafrost degradation. Capstone has modified operations or expanded a number of times since inception, and with each stage has been preceded by an environmental review and submission of a closure\remediation plan. The possibility of climate change plays an increasingly rigorous role in the planning and assessment process, and climate projections using down-scaled modelling produced by Scenarios Network for Alaska Planning (SNAP) are incorporated into the design process for the latest phase of mine expansion (November 2013). In this stage operations are to be moved underground, which may benefit closure and remediation because detritus will remain underground and not exposed to weathering.

Minto Summary of Climate Related Events and Responses

Minto Summary of Climate Related Events and Responses

Minto Summary of Climate Related Events and Responses

Outcomes and Monitoring Progress

There are relevant lessons for the mining industry from Minto’s experiences. These include the company’s clear acknowledgement of climate change as an issue, the re-visiting of climate projections as a basis for an engineering response to hydrological problems, investment in the range of responses to climate generated stresses over the past six years, the increasing partnership with the Selkirk First Nation in identifying and addressing potential environmental externalities affecting their Traditional Territory, and incorporation of long-term climate projections based on assumptions about warming in planning and remediation. Minto’s response to unanticipated climate related events can best be characterised as necessity driven adaptive management. While this reflects management versatility, the mine’s economic viability and marketing of ores in five year advance contracts gave it the capacity to bear the costs of responding and adapting as problems arose. A more economically marginal venture would perhaps be incapable of the same responses.