Passive Closure Mine Reclamation in British Columbia

In 2018, a slumbering industrial past was brought back into sharp focus for a community in Eastern British Columbia. Deep in the mountains, an inspection of a tailings pond embankment built in the early ’50s was deemed to need significant remediation work.

The RDCK took steps to move the Facility to passive closure by eliminating ponded water behind the dam, by increasing dam stability, and containing the tailings to prevent transport. Steps included:

• Developing a new spillway and eliminating the pond behind the dam.
• Covering the entire tailings area with 0.3-metre thick earthen cover.
• Creating lined surface water conveyance channels to direct water.
• Constructing a till beach upstream of the dam, and raising the dam’s filter layer.
• Expanding the toe berm at the bottom of the dam to improve seismic stability.

The HB Dam, located 10 km south of Salmo, BC, was initially constructed in 1955 to retain and store tailings from the nearby HB Mine, which was in operation until 1978, and decommissioned in 2005. After the earth dam of the tailings pond endured heavy rainfall in 2012, the HB Mines Tailings Facility became an environmental focus of the Regional District of Central Kootenay (RDCK). In 2016 it was approved for its passive closure, which includes stabilization of the dam and remediation of the tailings area.

RDCK issued A public tender to reinforce the topography, dewater the pond, and restore the natural habitat. Nominated as the general contractor, Integrated Sustainability led the project management, civil earthworks, geomatics, and construction remediation with an innovative value-added solution with assistance from Finning.

The passive closure of the Site required extensive planning and preparation to coordinate onsite activities over the course of two years. The project began by dewatering approximately 61,000 m3 of metal-bearing water that had accumulated behind the tailings pond embankment. Once the accumulated surface water was removed, the objective was to cap and cover the entire tailings area surface with a 0.3 m thick layer of clay till to prevent precipitation or surface water from coming in contact with the tailings material.

To further reduce the potential contact between tailings material and precipitation or surface water, we developed geosynthetically lined conveyance channels to direct surface water off-site. In addition to capping the tailings material, Integrated Sustainability also expanded the toe berm of the embankment to improve the seismic stability, improve the dam’s filtering layer, and reinforce the upstream beach area of the dam embankment.

The overarching goal of the passive closure was to prevent the transportation of metal-bearing material off-site during precipitation events or freshet. With the passive closure, the RDCK has moved the facility into an active care phase, which is anticipated to last between 3 to 5 years, where increased monitoring and oversight is complete to assess the passive closure performance.

With the site spanning over a kilometre in length in a remote location, Integrated Sustainability incorporated an innovative blend of geomatics, drone surveys, site management, and technology-enabled equipment to enable closer construction management.

This included setting up a SITECH® network to cover the entire project site, deploying geospatial drones to map out and survey the area, and connecting a modern fleet of Cat equipment’s built-in Trimble® GPS infrastructure to provide accurate and immediate insight into how machines were being utilized on-site. With all the equipment data available in a centralized, cloud-based dashboard that can be quickly and easily accessed off-site, the management team made informed decisions about how to manage the fleet in the field.

This methodology drives value through reduced equipment and operator hours and improves fuel efficiency. All of which further enhances the project’s environmental credentials upon completion.

Speaking to the project, Kris Kwiatkowski, Geomatics Manager at Integrated Sustainability, said:

“As a team, we are excited to see the outcome of this project improving the safety and sustainability of the region – and drive that knowledge and experience across other sites like this in British Columbia and around the world.“

With a blend of environmental and social risk management, responsible use of public funding, and a reduction of fossil fuel use, this project is an exemplary Venn diagram on ESG sustainability: closing the chapter on the past and paving the way for future remediation works.