Placer mining has over a one hundred year history in the Yukon Territory. The majority of placer mining has taken place in the zone of discontinuous permafrost. Within the discontinuous permafrost zone, vegetated valley flats and north-facing slopes generally are underlain with permafrost. The permafrost thickness is highly variable and may reach depths of 60 meters. The active layer covering the permafrost also varies greatly in thickness. To access gold bearing gravels, the removal of extensive quantities of overburden is usually required. Once this insulative cover is removed, the thermal equilibrium of the permafrost is disrupted and thawing occurs. This affects the stability of soils and vegetation and slope failure may occur. The extent that exposed permafrost melts depends partly on the amount and form of ice content. As melting progresses, the potential for mass movement of soil increases. Melting permafrost usually results in a wetter environment than was initially present, which further affects the natural revegetation process. Bioengineering is the use of living plant materials to perform engineering functions such as erosion control and stabilization of steep slopes. Although bioengineering methods are now commonly used in the stabilization of steep problem slopes in more moderate climates (Polster, 1997), experimentation with these techniques in areas underlain with permafrost is still required. Advantages of using bioengineering systems are that they can be installed without machine access (which in permafrost areas would disturb the site even more), they strengthen with age, and they are less expensive than traditional hard engineering practices.

With assistance from the Yukon Oil and Gas Branch, EDI Environmental Dynamics Inc. developed and submitted a proposal to the Mining and Petroleum Environmental Research Group (MPERG) to conduct a study of vegetation regeneration on linear developments subject to wildfires, specifically on and in the vicinity of the winter access road leading to test well site K- 58, beginning in the first post-fire growing season. The study site was located in sub-arctic, black spruce (Picea mariana) dominated forest in a zone of continuous permafrost in the area of Eagle Plains, YT. The study examined vegetation composition and abundance, as well as soil and permafrost conditions, in four types of linear disturbances, including: 1) burned 30+ year old seismic lines; 2) a burned one-year-old winter road; 3) the same burned one-year-old winter road constructed on an existing, 30+ year old seismic line, and; 4) unburned 30+ year old seismic lines. A total of 73 (200m2) paired vegetation plots were completed within each of the above linear disturbances and adjacent forests. Overall, the vegetation was highly uniform among all types of linear disturbances and undisturbed sites in the study area. Differences in species composition and abundance were most pronounced between the burned and unburned sites, with a greater number of species present and higher vegetation cover in unburned sites. Of the three types of linear disturbances sampled, the combined disturbance of the burned one year old winter road constructed on a 30+ year old seismic line demonstrated the most notable differences in vegetation composition and abundance in comparison with the adjacent forest. In contrast, species composition and abundance in the burned winter road and burned 30+ year old seismic line were more similar to that in adjacent, burned forests. No trends in soil moisture were detected among the various disturbance types. Depth to permafrost was slightly lower in all three linear disturbances, but this difference was not significant. Depth of organic soil was significantly lower in the combined disturbance of the burned one year old winter road constructed on a 30+ year old seismic line, and was significantly higher in the burned winter road, when compared to adjacent, burned forests. Moss depth was significantly higher in unburned than burned sites. In the first post-fire year, this recent burn appears to be the dominant factor affecting vegetation composition and abundance in the study area. Re-vegetation is occurring rapidly on linear disturbances, with the dominant vascular plant species in the unburned, undisturbed forest regenerating across all disturbance types. Because the study was completed in the first post-fire growing season, it was not possible to assess regeneration of black spruce, an important structural species that is not reported to begin to regenerate until several years after a burn. Similarly, it was also not possible to assess lichen re-establishment, an important element of vegetation succession in black spruce forest that also re-establishes later than the first post-fire growing season. Continued monitoring will be required to understand the longer term response of vegetation to fire in linear disturbances.

Reclamation testing was carried out on 3 mineral exploration sites in Yukon: an alpine site at the Red Ridge property in the Whitehorse area, and 2 subalpine sites, a boreal forest site at the Nucleus property in the Carmacks area, and a site in moist permafrost at the Hawk propeerty int he Dawson City area.

Considerable research has been carried out into the reclamation and revegetation of disturbed lands in the Yukon, including operating and abandoned mines, and mineral exploration sites in the Yukon. Reclamation efforts on tailings have focused on methods to establish an initial vegetative cover on disturbed areas. Guidelines have been established by Kennedy (1993) and Hill et al. (1996) for the optimum mixtures of fertilizer and seeds (both agronomic and native varieties)¿. ¿.A relatively new and unique method of tailings processing and disposal that is being used at a few mines around the world is called dry stacking. This method of tailings disposal has the potential to provide many benefits to mining companies and affords numerous environment advantages that slurry deposits do not¿. ¿.The purpose of this proposed project was to research current practices in other jurisdictions and to examine the best approaches for encouraging vegetative establishment on dry stack tailings in norhtern environments, particularly for potential mine sites in the Yukon.

Yukon’s northern oil and gas basins remained unglaciated during the Pleistocene. The absence of coarse aggregate material generated by glaciation, coupled with continuous permafrost, has required expensive programs of crushing and hauling bedrock for road and infrastructure development. This study examines fluvial deposits associated with the late-Pleistocene Eagle River meltwater channel as potential sources of aggregate for regional development. In particular, it applies a process-depositional model of meltwater channel development to understand the distribution and potential quality of aggregate resources in the area. We identify three zones with meltwater channel development: (i) an upper erosional zone (~ 50 km) of scoured bedrock associated with initial development of the channel; (ii) a middle zone (~ 35 km) of coarse deposition on high terraces associated with initial channel incision; and (iii) a lower zone (~ 75 km) dominated by fine lacustrine and deltaic deposits that likely overlie coarse fluvial deposits with up to 30 m of clay, silt and sand.

The Dempster Highway, Canada’s most northern highway, is an all-weather gravel road through a landscape that remains mostly wilderness. From its southern starting point (Km 0) east of Dawson City, Yukon, the highway crosses the Arctic Circle (latitude 66°33’ North) at Km 405. It passes from Yukon into Northwest Territories at Km 465, and terminates in Inuvik at approximately Km 717.5. The road also summits the continental divide between the Pacific and Arctic oceans (Km 82) and traverses two mountain ranges (Ogilvie and Richardson mountains) of the Canadian Cordillera. It is a spectacular multi-day journey, so take some time to enjoy it!

The effects of permafrost degradation in Yukon have serious negative implications for the structural integrity of vertical infrastructure. This is especially pertinent for critical buildings such as hospitals, schools, etc., in small communities that are situated on top of warm, ice-rich permafrost. Projections of mean annual air temperature over the next few decades, based on regional climatic models, indicate that air temperature will rise, hastening the thaw of permafrost. The combination of rising of air temperatures and buildings situated on warm permafrost has prompted this investigation into the vulnerability of Yukon Government vertical infrastructure. The application of DC resistivity and ground penetrating radar in conjunction with borehole drilling indicates that in Dawson there is warm ice-rich permafrost beneath the Palace Grand Theatre; the Old Territorial Administration building is underlain by primarily unfrozen sediment; and permafrost under the St. Andrew’s Church is characterized by high variability. A deep active layer was observed at Ross River School and geophysical surveys indicate that warm water drainage from the roof is contributing to the thaw of the underlying permafrost.

Permafrost is integral to the landscape of the Yukon, and influences hydrology and ecology, and impacts infrastructure. Accelerated permafrost thaw due to climate change poses significant challenges, particularly for the Alaska Highway, a vital transportation route. This study investigates how thawing permafrost may relate to ground instability, resulting in cracks and deformations along the highway. Thermal infrared imaging, and light detection and ranging (lidar) mounted on remotely piloted aircraft systems (RPAS), along with ground surveys, were completed at three localities along the Alaska Highway between the White River and the community of Beaver Creek, Yukon. Through these surveys, temperature variations and topographic changes were examined. At many locations, the damage is characterized by a 1 to 2 m-wide subsidence feature running longitudinally along the middle of the highway. Associated with these zones of subsidence are potholes, as well as longitudinal and transverse cracks. In places, the system of cracks extends to the edge and shoulder of the highway, suggesting that the cracks and deformation are currently active features.

Alaska Division of Geological & Geophysical Surveys (DGGS) has conducted 1:63,360-scale geologic mapping of the Sagavanirktok B-1 Quadrangle (640 square km�equivalent to four 7.5 minute quadrangles). This mapping project reinterprets micropaleontologic correlations for 17 Sagavanirktok Quadrangle wells, and reprocesses data from the one publicly-available seismic line. Surface geologic mapping, subsurface-to-surface stratigraphic age control, and seismic framework are required to reliably decipher the complex geology of this key area of the Brooks Range. Outcrops within the Sagavanirktok B-1 Quadrangle are the closest surface expressions of Prudhoe Bay source and reservoir rocks. This study yields critical petroleum-related information from these surface exposures, and how they relate to the area subsurface stratigraphy.

The Yukon is experiencing impacts of climate change, marked by elevated annual air temperatures, alterations in precipitation patterns and increased wildfire activity. These changes can lead to permafrost degradation, impacting highways and community Infrastructure. In July 2017, a wildfire burned a slope in permafrost terrain above the Dempster Highway in the Yukon. In the years following the wildfire, two types of permafrost-related landslides have been observed on the slope. Active layer detachment activity was highest in the first year after the landslide, possibly influenced by warm temperatures and rainfall events. Retrogressive thaw flow slides formed in 2019 in areas of ice-rich permafrost and are still active in 2023. Deposition of sediment and influx of water has resulted in flooding near the highway, further degrading the permafrost in the valley bottom. This study characterizes the landslide timing and morphology following a wildfire on permafrost terrain, and investigates potential triggers and controls.