Impact of diamond mining will not be forever

The right way to do mine reclamation is to start planning it before the mine opens, and long before it closes.

That's exactly what is happening at the site of De Beers' proposed Snap Lake diamond mine in Canada's Northwest Territories. The company's board recently approved the project and production is scheduled to start in 2006. Snap Lake will be De Beers' first diamond mine outside Africa and Canada's first fully underground diamond mine.

The construction cost will be an estimated C$636 million.

"I forget that sometimes, when I'm working with De Beers, that they're doing a mining project, not a revegetation project, but I also think it's good to stress that that's my focus and remind them of that," Sandra Marken, a plant ecologist with Golder Associates in Calgary, said at the Northern Latitudes Reclamation Workshop in May.

"Right now this is a plan that I'm presenting; we don't have any data, we haven't started revegetation, but there's things we can do up front that will help them down the road, in five, 10, 15, 20 and 25 years that will expedite the reclamation process," Marken said.

Switching to QuickBird satellite technology

Marken and her team used Landsat to map the vegetation, and they identified 18 vegetation cover types in the vicinity of the proposed mine. Heath-boulder and open water accounted for 85 percent of the area's vegetation.

Another 12 percent consisted of open spruce forest or tussock hammock, and various different vegetation types made up the remaining 3 percent.

Landsat did not provide a high enough resolution for the team's purposes, so this summer they will be switching over to the QuickBird satellite technology.

The focus of the reclamation will be at the north pile, a processed kimberlite and waste rock storage facility, Marken said.

The north pile, the mine buildings, the access road and the airstrip will form the footprint of the project.

The environmental impact assessment and monitoring program have so far looked at a 500-meter buffer around this footprint. The project's total area of impact is approximately 560 ha.

The north pile will be 484 meters wide, 1,200 meters long, 92 ha in area and rise 39 meters above the lowest local point, while not exceeding the height of the highest point.

Marken said that over the 22-year mine life it will be developed in three stages, and each stage, or cell, will be capped with half a meter of crushed granite, which will control erosion, but will also create some vegetation challenges.

After three years, reclamation will begin on the north pile's first cell.

"There has been some discussion with local communities as to whether they want to revegetate it at all, because of some concerns about plants growing on kimberlite, the possibility of accessing contaminants," Marken said. "In the planning of this north pile, it doesn't look like that will happen, however, we will monitor it to make sure it doesn't."

EIA's predictions tested annually

Work on the environmental impact assessment for the mine began in 1992 and it was approved in 2002.

The government's water license requirements added to the lengthy list of measures that De Beers has to implement in order to protect the environment.

The environmental impact assessment's predictions must be tested annually, to show the government and stakeholders that they are accurate, and that nothing unexpected is happening.

"We may have changes beyond the footprint that are affecting vegetation patterns, so we'll be measuring that every year, as well," Marken said. "We'll also be monitoring annually the results of reclamation and we'll also be applying adaptive management for continual improvement."

Two forms of monitoring

There will be two forms of monitoring, the annual monitoring and additional monitoring precipitated by predetermined triggers that signal potential problems - an early warning system.

If annual monitoring shows that the mine is disturbing more land than originally planned, or if the soil chemistry or water quality is different from the expected levels, that will trigger a site visit and possibly more investigation, and a more detailed monitoring program.

The other trigger program is the impact of dust, which is triggered by the annual air monitoring program.

After the environmental impact assessment was complete, a closure and reclamation plan was developed.

"It is a living document ... we'll expect changes as we go, and it'll also become more detailed as the program progresses," Marken said. "Right now a lot of our revegetation plans feel a little hypothetical."

Sharing information with other northern mines

De Beers and the reclamation specialists have committed to collaboration with other northern mines, to study changes to vegetation and soil properties if necessary, to monitor the effects of dust on vegetation, to incorporate traditional land use and knowledge in their program, and to train and work with local aboriginal communities. They will be exchanging information with BHP Billiton's Ekati diamond mine, also in the Northwest Territories.

Northwest Territories laws require De Beers to establish stable landforms, protect local water resources, re-establish productive use of the land, and facilitate the natural recovery of areas affected by mining. All of this is provided for in the closure and reclamation plan.

"Down the road, five, 10, 15, 20 years, if we want to find out if the mine is having an effect, or if we suspect it does, we'll have this pre-mine data to compare that back to, and I think we're fortunate to be able to do that," Marken said.