Victoria Gold’s Eagle Gold Project

Victoria Gold is responding to climate-related hazards to its mine site, such as permafrost degradation and shorter winter seasons, with a range of adaptive strategies, making it the first mine in the Yukon planned to anticipate events associated with a changing climate through its entire life cycle. Victoria Gold’s “Eagle Gold Project” is located in the Mayo Mining District of Central Yukon Territory, a region characterized by rugged mountainous terrain and harsh winters that has been intermittently mined for more than a century. It is estimated that there are 95 million tonnes of ore on the site, potentially yielding 2.3 million ounces of gold, and that the mine will have a lifespan of approximately nine years. The mine site is already experiencing a range of climate change-related impacts. For instance, permafrost degradation is affecting operations and the location of mine infrastructure. Increased freshets and summer precipitation is making river crossings vulnerable, which affects transportation to and from the mine site. And temperature variability on site is affecting site design and location of spoil-heap. Victoria Gold is responding to current and anticipated climate change impacts with a range of adaptive strategies, specific to each climate-related event. Examples include, relocating some infrastructure to minimize exposure to climate risks; monitoring of surface and sub-surface conditions throughout site; and using local geography to utilize different thermal regimes in siting spoil and waste heaps respectively.

Understanding and Assessing Impacts

Historically the major challenge facing mining in the Mayo region has been winter climate events, with extreme cold and snow and ice conditions and considerable seasonal variations in the hydrological regime affecting both mine-site conditions and transport. Winter temperatures average some -20 C and the area is underlain by discontinuous permafrost. Elevation, aspect, and seasonal weather extremes give rise to significant variations in local conditions. Local hydrology varies markedly through the year. Spring brings snowmelt, freshets, and consequent high water, while summer may be characterized by near drought conditions and low streamflow. Adapting to such extreme conditions has always been a fact of life for mining in this part of the Yukon, and historic adaptations included engineering to ensure mine and infrastructure were robust to withstand extreme winter and post-winter events, and to manage hydrological fluctuations. Operations were tailored to “the rhythm of the land”, with mines closed in winter and materials stock-piled in anticipation of transport disruptions or equipment failures. Mine planning was based on expectations of an extreme but more or less predictable annual climatic cycle and the notion that the future would be very much like the past. Winter climate conditions that historically impacted mining in the Mayo region remain the dominant hazard for contemporary operations. Snow accumulation and extreme cold adversely affect both equipment and transportation, and traditional responses in addressing these hazards come into play including infrastructure design and stockpiling of resources.

There is evidence that annual mean temperatures are increasing, and the Scenarios Network for Alaska and Arctic Planning (SNAP) has documented consistent increases in both temperature and precipitation in the Mayo Region over the past thirty years), and freeze-thaw characteristics are changing, with earlier ice break up and increased water flow swelling regional creeks and rivers and increased flooding. Discontinuous permafrost is present throughout the region, and because there is a long history of mining in the area it is known from both experience and science that permafrost underlying Victoria Gold’s mine-site is quite warm, and probably warmer than in the past, potentially giving rise to liquefaction risk.

Identifying Actions

Victoria Gold is responding to the region’s known hazards, and to uncertainties about future
climate trends. While there are indications that the local climate is changing, absence of good quality long-term climate data, and problems inherent in downscaling climate models in complex terrain make prognosis about future trends somewhat tenuous. While it may be accepted that local conditions are changing, for mine-planners and project managers gauging the appropriate response is difficult, especially when mines have a relatively short operating life. Answering the question “how much change to plan for through the operating life of the mine?” is fraught with difficulty and the answer has to be translated into hard business decisions, such as how much to invest in engineering responses to events that have not yet been experienced. In a broader temporal context because Victoria Gold is a new mine, it has full life-cycle-planning that incorporates expectations about climate change. The company pro-actively incorporated future climate considerations into operational design, and filed a remediation plan including climate modeling to identify probable conditions in post-closure environment.

Victoria Gold’s endeavors to reduce uncertainty are reflected in planning for the Casino mine, which included an assessment of future climate trends (next 40 years) (completed by Knight Piesold Consulting). The assessment examined past climate trends in the Yukon and utilized downscaled models to assess whether historical data can represent conditions that may prevail through the life of the mine. The report’s substantive conclusion was that there is considerable uncertainty about predictions of climate trends in the Yukon and that “potential changes be considered in climatic and hydrologic assessments, where appropriate”.

Implementation

The following is a list of Climate-Related Events and Adaptation Actions in Response:

  1. Permafrost on site – Permafrost in the vicinity of the mine-site is discontinuous, but is very warm (0-1C range) and indications are that it is warmer than in the past. Detailed monitoring and modification of site design to ensure stability of infrastructure and mine components.
  2. Variable temperatures associated with site topography – Site layout reflects microclimate variations
    and siting of spoil heap to take advantage of temperature differentiation.
  3. Extreme cold and snow accumulation – Building design (e.g. roof pitches) so that snow loading is not a problem. The spoil heap will be operative only two hundred and fifty days of the year because of snow accumulation.
  4. Hydrology and flooding – Freshets have always been problematic in this region, but over the last few years the incidence of floods has been increasing, and there is expectation that this trend will continue as winter thaw characteristics change. In recognition that the spring drainage regime may be changing site engineering is designed to accommodate 100-500 year events. Older culverts bridges and access roads from previous operations in the area are being replaced or upgraded. Essentially the precautionary principle is being applied, with over-engineering and building for high capacity events reflecting both the sense that the landscape is changing and compensating for the paucity of reliable climate data.
Victoria Gold Summary of Climate Related Events and Responses

Victoria Gold Summary of Climate Related Events and Responses

Outcomes and Monitoring Progress

While there is some evidence that climate in the region is changing there is considerable uncertainty about future conditions and trends because of the paucity of good quality standardized long-term data. Meteorological stations in this part of the Yukon are relatively few, widely distributed, lie in a variety of topographical contexts, and have varied recording histories. Victoria Gold is keenly aware of these data deficiencies, and consequently accessed climate model data and forecasting to assist in site planning. Climate modeling reduces uncertainty to some extent, but local topographic conditions and the paucity of long term local base-line data place limitations on the reliability of climate projections. Adaptation to this uncertainty takes two dominant forms. Intensive mine site monitoring to detail permafrost and hydrological conditions, and site planning and engineering to create plant and infrastructure robust enough to accommodate anticipated extreme events.