Not many people pay close attention to slag cement awards – but workers on the Giant Mine clean-up say winning one of the awards shows news from the mine isn’t all bad.
The Giant Mine project used slag cement last year to help fill a 70,000 square-metre chamber underneath the mine site, which is also home to more than 200,000 tons of toxic arsenic trioxide.
Filling empty, underground chambers stabilizes the mine site and helps to ensure underground areas are not flooded. Other chambers, containing arsenic trioxide, will be frozen by the remediation team to keep the material safely contained until an achievable solution that’s more permanent can be invented.
The chamber had to be filled by pouring backfill from the surface and letting it fall hundreds of feet into place.
That work won the project an innovation award from the Slag Cement Association, to be presented in April this year. Drew Burns, from the association, told Cabin Radio: “We haven’t seen a large-scale project like that use slag cement in this specific way.”
A cross-section shows, in different colours, how various substances were used to fill and stabilize a chamber beneath Giant Mine. The blue and pink lines represent boreholes from the surface used to fill the chamber.
Local contractors who carried out the work say that while most people’s pulses may not quicken at the sound of a slag cement award, the recognition is welcome at a time when the Giant clean-up is under scrutiny.
Leaders of the project spent last week listening to concerns at a public hearing as they apply for a water licence and land-use permit related to most of the clean-up work, which is still to come. The project has received criticism for a perceived lack of northern hiring.
“To me – and this is more the northerner in me – there’s a lot of not-so-great press on the Giant Mine site,” said Kenny Ruptash of contractor Nahanni Construction.
“But to me, the award speaks to the ingenuity and the innovation that the project team is coming with in the reclamation of the site.”
The Giant Mine project’s entry won even though the Slag Cement Association’s nomination forms specify entrants must be in the United States, Ruptash said.
“We’re starting to open it up to Canadian projects, too,” said association representative Burns.
To stabilize an underground chamber at Giant Mine, workers must pour backfill down boreholes from the surface. Photo: Nahanni Construction
“A lot of our members do business in Canada as well. When we see a project like that, even though its roots are in Canada, we’re happy to open our awards to quality use of slag cement. It was such a unique project.”
The main clean-up phase at Giant is expected to begin in the next 18 months, subject to acquisition of the appropriate licences and permits. Several hundred jobs are expected to be created, with proponents likening the economic impact to the opening of a small mine.
Correction: February 4, 2020 – 9:31 MT. This article initially reported that the chamber filled using this technique had contained arsenic trioxide. In fact, the chamber in question was empty. Filling the chamber helps to stabilize the broader mine site.