Whitehorse Copper Mine, within the city limits of Whitehorse, produced about 10 million tons of fine-grained calc-silicate tailings before its closure in 1982. The tailings, now desiccated, do not support plants although some areas have been undisturbed for more than 20 years. Barren tailings have high pH and electrical conductivity (E.C.) but are otherwise non-toxic.
The minimum requirements for sustainable plant growth are under study in a pilot project in which freely available compost from various sources was mixed with the uppermost tailings as a proto-soil. Six plots were initially treated with one dose of chemical fertilizer, regularly irrigated and protected from wind. Planted Yukon native grasses germinated and both transplanted trees and seeds in the compost survived. Grass growth was measured after 2 growing seasons and is directly related to the quantity and quality of the compost tilled into the upper 10 centimetres of the tailings. Soil texture, moisture retention and organic nutrients improved. Similar abandoned sites could benefit from the addition of readily available compost and the use of locally propagated seeds and native plants.
