Waste management schemes of potash mines in Saskatchewan

Abstract

Saskatchewan's potash industry, when operating at capacity, produces 28 × 106 t of salt tailings and 11 × 106 m3 of concentrated brine per year. As a result, in excess of 250 × 106 t of tailings and lesser amounts of brine are stored on the ground surface in waste disposal basins consisting of a system of ponds and dykes. While the substantial quantities of solid waste represent an enormous task for eventual decommissioning, it is the seepage of brine into the surrounding soil and groundwater that is presently of most concern. Four general models are proposed to illustrate the role of hydrogeology in the selection of techniques for containment of potash wastes. This paper reviews waste management schemes in the Saskatchewan potash industry over the past 27 years and presents observations and qualitative evaluations of waste disposal practice of four mines that are representative of the proposed hydrological models. The four case histories identify problems that are common to all mines. The importance of design, operation, and proper monitoring programs is emphasized. The study found that a combination of different seepage barriers have been reasonably successful in preventing serious brine contamination. Shortcomings, where they exist, have been caused largely by unsatisfactory design and construction practices. These inadequacies are of concern to the industry and government regulatory agencies, but they have not yet seriously impeded orderly potash waste disposal. Key words: waste management, potash tailings, brine disposal, brine containment, seepage barriers, seepage control, refining practices, brine ponds.