June 2010    Print this article

A Winning Partnership!

Agreement Between MRNF and OSISKO To Rehabilate East Malartic Mine

Louis Marcoux
Direction générale du développement de l'industrie minérale

Ministère des Ressources naturelles et de la Faune (MRNF) and Osisko will split the cost of rehabilitating the orphaned East Malartic mine tailings site located on the outskirts of the Town of Malartic. This is what both parties pledged in an agreement signed in March 2010 that will ultimately lead to the rehabilitation of the East Malartic mine. The partnership, which is a great example of sustainable development principles in action, boasts numerous advantages. Among them, it will make it possible to rehabilitate the site at considerable savings to the government, begin operations at the Osisko gold mine immediately and at no additional cost, minimize the amount of natural resources (sand, gravel, clay, etc.) needed to rehabilitate the site, and sidestep the need to build a new large scale mine tailing site and thus avoid disturbing other regions.

The price tag for rehabilitating the site, which has been under government responsibility since 2004, is evaluated at $23 million. In summary, the work consists of covering and neutralizing the existing acid-generating tailings with tailings produced from the Canadian Malartic mine. Work to build a polishing basin and develop a mine tailings site is already underway.

Background of the orphaned East Malartic mine

MRNF has been responsible for the East Malartic site since 2004 following the bankruptcy of the McWatters Mining Company. The McWatters Mining Company had acquired the site from the Barrick Gold Corporation in 2003, and it planned to process ore from the East Amphi mine there. In taking ownership of this area, MRNF’s first order of business was to ensure the site’s safety. It also carried out mine effluent monitoring in accordance with all provincial and federal regulations. A number of sources were used to finance the priority work to secure the premises, including a financial security of over $2 million from the McWatters rehabilitation fund.

Thickened tailings used in site rehabilitation project for the first time in Québec!

In the last 20 years thickened tailings have been used to backfill underground openings. This will be the first time they are used to cover acid-generating tailings in Québec. Since thickened tailings have solid material concentrations of between 65 and 70%, they can be used to stock a higher volume of tailings in a smaller area. Thickened tailings look like a non-segregative paste with little or no free water. They form cone-shaped cells of various heights. To avoid overflows, a sterile stone wall will be built around the various cells.

The expected daily production of 55,000 tons of tailings will make it possible to cover all the acid-forming tailings at the East Malartic mine in a layer at least three meters thick in the next three years. Thickened tailings have hydric properties that allow them to remain saturated with water, which enables them to slow the diffusion of oxygen and curb acid drainage.

A win-win agreement

The agreement will end once MRNF receives notice from a specialist confirming that the East Malartic tailings no longer generate acid mine drainage. This win-win agreement is similar to that signed in 2006 with Agnico-Eagle Mines to rehabilitate the orphaned Manitou mine. These are outstanding examples of how to incorporate sustainable development and land-use principles in mining projects. They could be repeated in other areas disturbed by mining, or even used to rehabilitate sectors damaged by other industrial activities.



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