Case Study
Rabbit Lake Reclamation
Cameco seeks to maximize the useful life of its milling facilities to reduce environmental impact. We would rather transport ore to an existing mill than construct a new one in a new place.
The Rabbit Lake operation has been producing uranium since 1975. Five ore bodies have been mined and milled at the site. Rather than waiting for final decommissioning, Cameco is reclaiming inactive facilities such as pits and waste rock piles as part of continuing operations.
In 2009, Cameco implemented a site-wide reclamation plan for Rabbit Lake. The plan covers all facilities used in mining and waste management on the site. The facilities are reclaimed to a high standard which, in most cases, is expected to be accepted by regulators as final decommissioning when the time comes.
An example of the work being completed under the plan is the B-zone waste rock pile. The facility holds 5.6 million cubic metres of waste rock that resulted from mining B-zone ore body. The challenge is to ensure that groundwater interaction and runoff from the waste rock does not affect the surrounding environment and to blend the facility into the surrounding landscape.
“There’s a lot of time on the front end to do the studies, making sure that you have a very high level of confidence that the design will work over the long term,” said Kirk Lamont, Rabbit Lake’s manager of safety, health, radiation, environment, quality and regulatory affairs. “We want to make sure that it’s sustainable over hundreds of years.”
Before the pile could be blended back into the environment, the physical and chemical make-up of the rock, along with groundwater flows, had to be studied.
“From a technical standpoint, we did very detailed work to understand the waste rock and what might leach out,” said Barry Esford, manager, geo-environmental engineering. “Then we had to design a cover that would help to minimize infiltration.”
The plan involved reshaping and contouring the pile to control erosion and prevent slope failure. The surface was then compacted to decrease permeability. One metre of glacial till was then placed to create an effective cover. The final step involved hydroseeding the cover with native grasses in the summer of 2013.
“The cover is designed to store excess precipitation and then the vegetation is the mechanism to release it,” Esford explained. “You want to have enough till on top so that if you get a lot of precipitation, the cover is capable of storing it. You also want to have enough storage capacity to support the vegetation through dry times.”
Site-wide reclamation work has progressed steadily in recent years. Two of three former open pits along the shoreline of Wollaston Lake’s Collins Bay have been reclaimed. And more recently, an engineered cover and a layer of glacial till has been placed over a substantial portion of the above ground tailings facility, again to better store and release surface runoff and reduce groundwater infiltration.
Visitors from nearby communities who are members of the northern Saskatchewan Environmental Quality Committee (EQC) have made annual visits to view reclamation projects and understand their purpose.
“One of the members of the EQC used to work at Rabbit Lake, so we were showing him what we did with the waste rock pile and how it’s working,” said Lamont. “Watching his reaction was very rewarding.”