Placement of solid wastes in dissolved caverns in salt is increasingly being viewed as an environmentally secure technology for low-toxicity wastes such as foundry sands (heavy metals), contaminated soil and other granular solid waste streams. Costs of salt cavern disposal probably eliminates their use for large volumes of non-toxic wastes, but permanent entombment of toxic materials in salt caverns is economically competitive to other alternative disposal or storage approaches. Salt caverns in Alberta and Saskatchewan at depths of 1,200-1,500 m are being used for disposal of non-toxic materials (non-hazardous oilfield wastes) and for storage of natural gas and liquids (propane, glycol, etc.). Low to medium toxicity oilfield wastes can be economically and securely placed in salt solution caverns using an engineered slurry approach. Effective cavern disposal requires a design and monitoring strategy to optimize cavern utilization and to demonstrate environmental security for waste containment.
This article is conceptual in nature; however, its conclusions and observations are based firmly on extensive laboratory, field, and modeling experience in salt rocks, applied to caverns and to underground mines.
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