ACID MINE DRAINAGE FROM ABANDONED MINE SITES: PROBLEMATIC AND RECLAMATION APPROACHES

摘要

One of the most serious environmental issues related to the mining industry in Canada and elsewhere, is the pollution from abandoned mine waste disposal sites. The wastes containing sulphide minerals can oxidize and generate contaminants in the water drainage, a phenomenon called acid mine drainage (AMD). Different techniques are available to control the production of AMD. However, these techniques were mainly developed for the closure of operating sites, and are not as efficient for abandoned mine sites that were left exposed to natural conditions for years. The main differences between an operating and abandoned mine waste disposal site are the quality of the interstitial water, the presence of well implemented acidophilic bacteria, and the quality of the retaining infrastructures. To avoid contamination of surrounding ecosystems, it is necessary to take into consideration these particularities at the reclamation stage. The experience at the Lorraine mine site shows a slight improvement of the water quality in the waste disposal site 10 years after reclamation even if the oxygen barrier is working as expected. The addition of a passive treatment system to treat the contaminated pore water that will eventually flow out of the site is then a critical component of the reclamation at any abandoned AMD mine waste disposal site.