Acidic drainage resulting from the oxidation of sulphide minerals is the single largest environmental problem facing the Canadian mining industry today. Sulphide oxidation, which generally occurs at shallow depths above the water table, can result in the production of highly acidic pore water containing elevated levels of many heavy metals and other deleterious constituents. It is generally agreed that the production of acid is controlled by the availability of the oxygen at the sulphide surface. In tailings the primary mode of oxygen transport is diffusion through porous spaces. An impermeable cover can eliminate or significantly alleviate the problems related to the acid mine wastes.

The Alberta Research Council (ARC) proposed to use its newly-developed super absorbent polymer (SAP) for the abatement of acid mine drainage. SAP is a patented product and is made of polyacrylamide-modified clay. When fully hydrated, one gram of SAP can adsorb more than 650 grams of fresh water and increases its volume significantly during the process. This very property of SAP could be very useful in the area of acid tailing abatement.

Preliminary tests with the SAP/sands mixture show a significant potential for SAP application in acid mine tailing abatement. Addition of 1 wt% of SAP into a medium sand can lower its hydraulic conductivity by four orders of magnitude. Moisture retention capability can also be increased significantly. The use of SAP in a bottom liner of a tailings pond is not a viable option because the poisoning effect of multi-valent cations on the SAP. However, a SAP-bearing cover should be an effective hydraulic barrier. Essentially, the cover would be an impermeable barrier and would retain its water saturation. If used in 0.2 wt% concentration, the cost of SAP will be about 1/20 of the total cost for the construction of the cover. The cost for this material may be offset by the savings on the transportation of another barrier material and construction of the cover.