Reclamation and Vegetation of Surface Mined Areas in the Athabasca Tar Sands

One of the major environmental problems which arises with surface mining of the oil sands in the Fort McMurray-Fort MacKay area of Alberta is the permanent loss of the natural vegetation and the drastic change in the soils that supported it. It has been estimated that with a production target of one million barrels of crude oil per day approximately two thousand acres of land will have to be cleared every year. Most of the disturbed areas eventually must be vegetated again; these include the overburden piles and the tailings sand. In vegetating such areas several problems such as salinity, oil, low fertility, erosion and unfavorable soil reaction have to be contended with. There has been some success in the general vegetation program on the Great Canadian Oil Sands Ltd. lease, but the problems listed above still have to be studied and solutions for them found. Surface mining of the Alberta oil sands requires the clearing of natural vegetation from thousands of acres of land. Under other circumstances these cleared areas should present few problems for revegetation programs, but major problems arise in mined areas and in areas where mine wastes are deposited. The wastes include tailings sand, overburden materials (which may contain oil-bearing materials and may present salinity and alkalinity problems), and coke and sulfur (by-products of the upgrading process which could damage vegetated areas through wind-blown dust deposits). A likely problem in the future is the damage that would be caused over wide areas to the soil and vegetation by the sulfur dioxide emissions from the processing plants. The only operating plant in the area, Great Canadian Oil Sands Ltd. (GCOS), has embarked on a program to vegetate the tailings pond dike, whose outer shell consists of tailings sand, and also the overburden piles. Investigations carried out over a one-year period examined some of the materials at hand and techniques available for solving some of the existing known problems in vegetating the mine wastes. A number of plant species, both cultivated and native, were grown in growth chambers on the waste materials to determine the performance of the species under different salinity, soil reaction, fertility, soil mix, and oil conditions. A second major study, a field trial on an already vegetated area on the GCOS tailings pond dike, was conducted to determine responses of the already established vegetative cover to different fertility levels, and to determine the fate of added fertilizer nutrients. The materials used in preparing various "soil mixes" were characterized chemically and biologically.