Mosaic begins new phase of K3 mine
The twin tunnels of the K3 mine near Esterhazy are the first new potash shafts created in Saskatchewan in nearly 50 years, and, in February of this year, they finally reached their target deposit. With the technical hurdles of sinking the shafts cleared, Mosaic has begun to construct the underground facility that will operate for decades to come.
Tunnelling to a point 3,350 feet below the surface was no easy matter. “Shaft-sinking is a very challenging activity,” said Gerry Couture, Vice-President of Capital and Engineering at the K3 mine. “All the work is in one tube all the way down; hoists have to lower people and equipment up and down. People are generally working off a big structure that we suspend down there, which is called a Galloway. There are a lot of challenges that have to be met, because you have to watch out for things like falling objects and controlling what’s going on in a small footprint.”
Potash mining in Saskatchewan holds its own special obstacle in the form of the Blairmore Formation, a geological layer of sandy soil in which high-pressure water awaits to sabotage access to a water-soluble salt like potash. “In the early to late 1950s, attempts to sink shafts through these formations failed because they could not contain the water, and they ended up with flooding,” said Couture. “It was at that time, in the early ‘60s, that they started using freezing technology.”
Although the technology to freeze these formations has advanced, it still requires considerable planning and resources to implement. “Each shaft had about 36 wells drilled around it,” said Couture. “We had a big refrigeration plant, so we circulated refrigerated liquid into these wells and actually froze an entire ring around the shaft to a depth of 1,600 feet. That allowed us to sink through frozen ground for the first part of the shaft-sinking, get through and install the liners that are required to seal off the formation.”
After passing the formation, other smaller pockets of water-bearing rock remained, but sealing them was less of an undertaking. “To get through those formations, we use a process called ‘Curtain Grouting,’” said Couture. Each time that “the bench” – what miners call the bottom of a shaft at any given time – reaches such a formation, miners would drill hundreds of small holes downwards and outwards from the shaft. “We would inject a fluid grouting material into these holes and fill up the void spaces that allow water to flow.”
As the shafts deepened, workers constructed permanent liners from the tops of the shafts to the bottoms to prevent the inflow of water, or any other hazard, from ever becoming an issue. “The liners will be intact and will actually serve as part of the way that the shafts are finally sealed off,” said Couture.
In mid-February of this year, the K3 shafts finally encountered the potash deposit that was their goal, and the project reached a literal turning point as the direction of the tunneling shifted from vertical to horizontal. The two shafts were linked, and closer surveys were performed.
Fortunately, one of the advantages of the local potash deposits is their stability, and that allows for “room and pillar” mining. “It’s a type of mining where you can go in long, straight runs with the four-rotor mining machines to be quite efficient,” said Couture. “You’ll cut long, straight rooms for extracting ore, but you’ve got to support the rest of the world above you, so you leave a section that becomes a pillar, and then you do another room a certain distance over.”
Essentially, mining at that depth requires the construction of an entire subterranean support facility. “What we’re doing is creating shops underground – an electrical shop, equipment shops,” said Couture. “You’ve got to be very strategic in how you cut these rooms and handle the mucked material in order to create the facilities that you’re looking at. There’s a lot of planning that is required for this underground work – much more than, say, surface construction.”
Currently, the crews that sunk the shafts are applying their expertise to the initial development of the underground portions of the mine, but other skill sets will soon be required. “Now that we’ve created some space and can start getting some other equipment down, we will be bringing in other types of trades in there for construction of steel and the infrastructure that we need there,” said Couture. “For example, there’s a lot of steel that has to go in on the shaft bottom to be able to support the equipment when we establish the permanent hoist for operation.
“It’s going to be a very efficient operation with the new mine, with state-of-the-art technologies in pretty much every aspect of equipment and procedures,” said Couture. “Mosaic’s investment in this mine and Esterhazy will really bolster the community and Mosaic for the next several decades as that mine moves into full operation and expands to full capacity.”