Post-Mining, a Crucial Step

The Aldermac site is a former copper and zinc mine that operated from 1932 to 1943 and generated 1.5 million tonnes of highly acid-generating mine tailings without any containment measures. From 2008 to 2010, the MRNF carried out restoration work at the former Aldermac mine site, including the addition of an impermeable liner (geomembrane) to a cellular containment following excavation and the liming of tailings in the southern sector, as well as the installation of a monolayer cover and an elevated water table in the northern sector.

A performance gap analysis of restoration methods for mine sites restored by the MRNF, carried out in 2020 by the IRME-UQAT, raised a number of issues regarding the environmental performance of restoration work at the Aldermac site.

The MRNF therefore decided to set up a committee of industry and academia experts to shed new light on the environmental situation at the former Aldermac mining site. The main objective of the committee was to analyze and understand, as much as possible, the post-restoration behaviour of the Aldermac mine site in order to propose a work programme aimed at finding lasting solutions to control the site’s environmental contamination.

This presentation will describe the main conclusions of this work.

Setting up a post-restoration monitoring and maintenance programme for a mine site is important in every respect. It ensures that the restoration objectives have been met, that the integrity of the structures in place is maintained, that the performance of the engineering structures is monitored and that the overall degradation of the site is avoided. In Quebec, a number of restored mine sites are under the responsibility of the State, and the team at the Service de gestion des sites miniers abandonnés (SGSMA) of the Direction de la restauration des sites miniers (DRSM) is responsible for monitoring and maintaining them. This session will introduce our team and provide an overview of their achievements and the main challenges they face.

Agnico Eagle Mines Ltd. is the largest gold producer in Canada and the 3^rd largest in the world, with 11 operating mines in 4 countries. In the shadow of the headframes of its operating mines, Agnico Eagle also owns several historic properties, either inactive or temporarily suspended. Managing these properties, of which more than 250 are located in the Cobalt and Kirkland Lake mining camps in Ontario, requires careful thought and a vision that goes beyond the applicable regulations.

Agnico Eagle set up a corporate team dedicated to mine reclamation in 2014. While each operation is responsible for developing and updating its reclamation plan, which includes post-closure and post-reclamation monitoring, the mine reclamation team supports and revises as needed to ensure consistency across the company. When operations cease, the mine reclamation team joins a dedicated team from the operation and takes charge of dismantling the site. The corporate team is also responsible for historic or inactive sites, monitoring and rehabilitating them.

How are responsibilities transferred between the operation and the corporate restoration team when operations cease? Who is involved in post-closure and post-reclamation monitoring? What is the role of the designated engineer? How are differences in legislation or the absence of legislation on closure and reclamation addressed in the various jurisdictions where Agnico Eagle operates? The development of an internal standard, a gap analysis grid and guidelines (currently being drafted) will provide greater clarity and standardize procedures within the company.

This conference will focus on Rio Tinto Aluminium's (RTA) vision and culture for the closure and reclamation of mining sites, including the Bauxite Tailings Deposition Site (BTDS). We'll look at RTA's global approach and how this translates into BRDS operations for the mining of active cells and the progressive restoration of accumulation areas that have become inactive. The second part of the presentation will focus on the portfolio of research and development projects for the valorization of bauxite tailings and the key elements of the various technologies under study. These technologies could play an important role in reclaiming mine sites, both for the technical aspects of the projects and for the community. These technologies, which are at different stages of development or maturity, enable RTA to increase the circularity of its industrial activities by transforming tailings from past and present operations into resources and manufactured products for other uses.