| Popis: |
The Louvicourt sulphide deposit, located 20 km east of Val-d’Or, Quebec, was discovered in 1989. Production of copper and zinc concentrates was initiated in 1994 and ceased in 2005 due to exhaustion of the ore body. The ore and some waste rock from mine development were acid-generating. Early in the mine planning, issues related to protection of the environment and to mine closure were considered. To limit environmental impacts related to acid-generating milling residues, it was decided to take advantage of the paste backfill plant by using 55% of the milling residues to incorporate them in the cemented backfill. The latter was used for ground support in mined stopes. Sub-aqueous disposal of mill tailings (remaining 45%) was selected at the project design stage to inhibit acid generation. An artificial pond was built in a suitable area located 8 km northwest of the mine. The pond is confined by natural topography and dikes. A polishing pond was added to improve final effluent quality. The retained concept involves maintaining the dikes and water cover in perpetuity. As required by the Quebec Environmental Act, an Environmental Site Assessment was completed following mine closure. Based on results obtained at Louvicourt, 76,000 m³ of backfill material around the infrastructures were contaminated by dust containing copper and zinc due to the routine handling of ore, waste and concentrates. In addition, part of a barren waste pile was slightly acid-generating (66,000 m³). The site was rehabilitated in 2007 by excavating and placing these materials in the underground workings and on an existing acid-generating waste rock pile that remains to be remediated by installing an impervious cover. Five years after mine closure, the water quality at the tailings pond is good and meets the requirements defined by Quebec Directive 019 on the mining industry. Water in the polishing pond meets Quebec fresh water quality criteria (acute toxicity). The tailings impoundment system is proving to be very efficient at preventing acid generation. Over the long-term, it is anticipated that some portions of the site can be returned to the crown. |
