Compatibility of Containment Systems with Mine Waste Liquids.

Background/Need:
Great interest has arisen in metallic mining at various locations in Wisconsin. Significant concern has developed regarding the potential for environmental impacts of mining, particularly the pollution of groundwater. This concern has arisen due to the poor environmental track record of most mining companies.

Mining’s greatest threat to groundwater is pollution from drainage of mine tailings. Tailings are the residue remaining after benefication of the ore. Drainage from tailings may consist of process water present at the time of disposal or acidic water caused by percolate passing through tailings undergoing oxidation. Acidic mine drainage pollution is characterized by a low pH and elevated concentrations of heavy metals affecting both surface and groundwaters.

One method to prevent groundwater contamination is to place tailings in an engineered waste containment facility designed using the principles employed for modern municipal and industrial landfills. Design of an engineered containment system consists of reducing the leakage to a negligible amount so that the only important contaminant transport mechanism is molecular diffusion. Recent studies sponsored by USEPA have shown that modern landfill liners do perform as intended and have very low leakage rates typically less than 30 L/ha-d (1 mm/yr). However, mine tailings are very different than municipal waste and stabilized hazardous waste placed in industrial landfills. Thus the lining systems used for municipal and industrial waste may perform differently when they are exposed to mine drainage. In fact, an extensive review of literature has revealed no case studies regarding the environmental performance of engineered containment facilities for tailings. Therefore, efficiency of the lining systems used for mine waste containment must be assessed in order to make responsible decisions regarding mine waste management.

Objectives:
The main objective of this study is to assess the compatibility of lining system materials and mine waste liquids, with the intent of determining if materials used for lining systems will function as intended when they are exposed to mine waste liquids. The second objective is to predict the lifetime of lining system materials by extrapolating the experimental behavior to site-specific conditions.