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.

Placer mining occurs extensively in parts of the Yukon, denuding riparian zones and lining valley bottoms with mine tailings. Revegetation of tailings was examined at two placer mines near Mayo to determine the influence of environmental variables on the speed and direction of the natural process. Vegetation species density and frequency on various substrates were compared with: age, slope and aspect of the site, and pH, particle size distribution, moisture content and organic content of the soill. In central Yukon, tailings are first colonized by ruderal (weedy pioneer) species such as fireweed and members of the Compositae (dandelion) family. These are replaced by willow-dominated communities after nine years. Willow communities support many species characteristic of the adjacent undistrubed black spruce forest, suggesting that the placer succession is similar to that of riverbank environments in interior Alaska. Revegetation of the tailings proceeds at the same rate for the first twelve years as does that following natural disturbance. Of the environmental factors examined, only age and slope were, statistically, associated with rate of revegetation. Both the percent cover and the number of species at a site were inversely associated with slope, suggesting that reduction of slope angle enhances vegetation regeneration.

In July 2009 we re-visited the re-vegetation experiments, which had been set up on tailings in the period 2003-2006. The three experimental sites are at Mount Skukum, United Keno and Wellgreen. The experiments consisted of either seeding the tailings with various populations of the tufted hair grass and/ or with stratified (cold temperature treated) seed of the shrub soapberry, or making transplants of the same two species. The treatments included the addition of compost from the City of Whitehorse, addition of fertilizer as 7:7:7 pellets, addition of organic matter as sheep manure, peat or woody debris from on site and, in the case of Wellgreen, a lime addition to overcome the strong acidity. The results are striking and illustrated in the Plates 1-15. Data of performance and flowering success are shown in the Tables, as are chemical analytical data in the Figures and Tables. Plots set up in 2003 provide a nucleus for effective re-vegetation, having survived for 6 years. The success of the seedings and transplants at Mount Skukum and United Keno was good, while that at Wellgreen was very poor. Wellgreen has suffered flooding with washing out of plots and washing out of the neutralizing lime. Nevertheless, in compost additions plots at Wellgreen, set up in 2005 and 2006, a small amount of re-vegetation and survival has occurred, especially in the wetter areas near the tailings pond.

Fieldwork was completed in July/August, 2001 in northern Yukon. Fieldwork included investigating results from the stream sediment geochemical survey commissioned to the GSC in the summer of 2000. This survey had been designed to complete the geochemical coverage over the Eagle Plains ecoregion, cover the transition zone between neighboring ecoregions and fill a gap in RGS coverage between pre-existing surveys. The 2001 fieldwork was designed to investigate the most significant RGS anomalies, prospect for mineral occurrences, sample the stratigraphy to determine background metal content, document the geological environment and collect information with the objective of adding to the understanding of the mineral potential of the area.

The revegetation of northern tailings sites presents many challenges. By using plants, which are naturally adapted to both the tailings environment and northern climatic conditions, fewer amendments and intervention will be required. In 2003, vegetation growing on and off the tailings and soil at three Yukon Territory, Canada, mine sites (United Keno Hill, Mount Skukum, and Wellgreen) was assessed and soil samples were collected. Through Canonical Correspondence Analysis (CCA), a statistical program that assesses relationships between plant species and environmental variables, I found that these plant communities are largely governed by a chemical-nutrient gradient (heavy metals and nutrients) and a ground cover gradient (bare and exposed conditions compared with full ground cover). The native grass Deschampsia caespitosa L. Beauv. was found colonizing all three tailings sites and its presence was associated with low nutrients, high heavy metal levels, and exposed ground, but it was also a habitat generalist. Five Yukon populations of D. caespitosa, originating from mine and uncontaminated sites were tested hydroponically for their tolerance to elevated Ni, Zn, and Cd concentrations. Intrinsic multiple metal tolerance occurred in all populations. In revegetation field trials in the Yukon, I planted seeds and transplants of 7 populations of D. caespitosa under different treatments: i) untreated, ii) compost, iii) fertilizer, and iv) combined (compost and fertilizer). At all sites, during the two years of data collection, local and non-local populations, including those from non-contaminated sites were able to establish, grow, and reproduce, even in unamended tailings and despite successive hot and dry summers. D. caespitosa also acted as a nurse crop, facilitating invasion of plants from adjacent habitats. The short term results suggest that the inclusion of Deschampsia caespitosa as a nurse crop for the revegetation of these northern mine tailings sites will be beneficial.

Revegetation projects in Yukon typically involve reclamation and erosion control of disturbed areas from mining and road construction related activities. The general purpose of the revegetation is to restore or stabilize these disturbed areas. However, because of Yukon’s harsh climate, lack of precipitation, and higher latitude, the success rate of various revegetation efforts is variable. Revegetation techniques used with success in more southern locations are not guaranteed to work here and little is available in terms of comparative evaluations of their use in Yukon. This report provides a summary and an evaluation of various revegetation and erosion control projects completed mostly in the past 15 years. It describes their successes and failures in an attempt to provide a guide for future restoration work and to help improve success (Section 3). Section 4 of the report provides an overall review summary to capture the essence of the various techniques. We end the report with a short list of recommendations for future work in Section 5 and acknowledgements in Section 6. Summaries of monitoring information from each site reviewed are presented in Appendix A.

There have recently been many changes in the way mining exploration projects operate, including new technologies, new exploration targets and new environmental regulations. Following recent amendments, to the Yukon Quartz and Placer Mining Acts, a significant new piece of legislation came into effect in December, 1999. The Yukon Quartz Mining Land Use Regulations, administered by the Department of Indian Affairs and Northern Development, now requires the reclamation of disturbed land on mining claims. But what happens at these reclaimed sites several years after the work is finished? Is there more than one way to successfully reclaim such land? How do local conditions affect the regrowth of plants on these sites and how much preparation of the reclaimed surface is needed? This report may not provide answers to all these questions, but it presents data collected at several Yukon sites, each with different ages and having had different reclamation treatments. From these observations, patterns on the success or failure of revegetation programs emerge and provide information on the rate and extent of natural revegetation at reclaimed mining trenches. Several types of reclamation sites were looked at in several different areas of Yukon, both above and below the treeline. Three of these were exploration trenches that were backfilled and revegetated as part of an experimental reclamation program in 1995. These reclaimed exploration sites included the Red Ridge trench, near Annie Lake in the Whitehorse area, the Nucleus trench, west of Carmacks and the Hawk trench near Dawson City. Each of these reclaimed trenches were revegetated with different seed and fertilizer mixes. This report summarizes how these sites looked in 1999, four years after the reclamation work was done. At Division Mountain, west of Braeburn, several coal trenches and drill pads were reclaimed by a mineral exploration company between 1995 and 1997. These sites were also looked at in 1999 in order to measure the success of the revegetation program. The last place visited in 1999 was Jason Knoll near Macmillan Pass where a number of exploration trenches and drill pads were reclaimed in the early 1980s. This site provides a look at the longer-term success rate of a revegetation program near the treeline. Refilled and contoured trenches, with rough and loose surfaces seem to revegetate well. The replacement of original soil is most important and makes the most significant contribution to the revegetation process, particularly at high elevation sites or sites in extreme climatic conditions. The replacement of tree debris significantly improves habitat conditions for small mammals by decreasing access and visibility for predators.

In the Yukon, the goal of most reclamation programs is to return disturbed lands as close to their original wildlands state as is feasible. The revegetation process, an integral component of reclamation, can be manipulated in ways to reflect this ultimate land use objective. The report reviews past Yukon reclamation practices and looks at how natural successional processes can be encouraged on lands disturbed by mining and mineral exploration practices. By examining the factors that affect the successional patterns of revegetation on disturbed sites, and by noting the composition of plant communities that colonize these areas, the most appropriate pioneering shrub species can be selected for assisted revegetation programs. The species selected for revegetation must reflect each site's ecological variables, as well as the nature of the mining-related disturbances. The reclamation potential of Yukon native shrub species is discussed in this report, along with techniques for assisted revegetation, including the collection of plant materials and propagation methods. The reclamation capabilities of 23 locally occurring shrub species is appended to this report. This information has been extracted primarily from vegetation experimentation in Alaska and northern Alberta. In order to determine whether these native shrubs are viable as species for reclamation work in the local environment, seeding and planting trials are recommended at Yukon mine and mineral exploration sites.

This project was undertaken to evaluate the potential to economically recover additional metal values from the 4.6 million tons of Keno Hill flotation tailings which grades 3-4 oz/t silver, 0.8% lead and 0.9% zinc. The study determined that the higher grade portion of the tailing, containing some 1.0 million tons at 5.35 oz/t Ag, responds well to cyanide heap leaching with a silver recovery of 50-60%. The testing data suggests that heap leaching is economically feasible at the current silver price of $US5.50/ounce and a currency exchange rate of 1.35 in favour of the US dollar. The response to gravity and flotation concentration was poor.