Jansen is an underground potash development project. Credit: hydebrink/Shutterstock.com.
The Jansen mine will be among the largest potash mines in the world, upon commissioning. Credit: Pictureguy/Shutterstock.com.

The Jansen project is a proposed underground potash development project in east-central Saskatchewan, approximately 140km east of Saskatoon, Canada.

Owned by BHP Billiton, the mine will be one of the world’s largest potash mines, producing eight million tonnes per annum (Mtpa) of marketable potash at full capacity.

The project advanced to the feasibility study in February 2011. Development of the mine to full capacity will be carried out over three phases, at an estimated cost of more than $12bn. BHP has invested approximately $4.5bn in the project since 2008. The mine will operate for an estimated life of up to 100 years.

The final investment decision (FID) on the first stage (Jansen S1) of the potash project was made in August 2021. BHP will invest C$7.5bn ($5.7bn) in Jansen S1, which is expected to have a production capacity of approximately 4.35Mtpa of potash. First production from the mine is expected in 2027. The construction phase will last six years while an additional two-year ramp-up phase will expand the production.

The Jansen S1 will involve the design, engineering, and construction of an underground potash mine. It will also create a processing facility, a storage facility, and a continuous automated rail loading system. The ore produced from the Jansen S1 will be exported through Westshore Terminals in Delta, British Columbia. BHP will also provide funding for the development of the required port infrastructure.

The potash project is anticipated to generate approximately 3,500 jobs a year during the construction phase and more than 600 direct jobs, upon commissioning.

Jansen potash project geology and mineralisation

The Jansen resource lies within the locally extensive and consistent Prairie Evaporite formation, which forms part of the Elk Point Basin. The regional geology is classified into three stratigraphic segments.

The deposit is hosted at a depth of 900m to 1,000m. The main potash bearing zone plunges gently from the north-east to the south-west. It is underlain by a sequence of limestone, dolomites and anhydrites that host reef mound sequences known as Winnipegosis. Overlying the zone are the Mannville formation, the Davidson Evaporite and Hubbart Salt formations, the Dawson Bay formation, as well as collapse structures.

Also known as the Blairmore formation, the Mannville formation comprises a sequence of clean sandstone interbedded with shales. The Dawson Bay formation hosts two halite beds, the uppermost Hubbart salt and the Davidson Evaporite. The two halite beds are separated by an anhydrite bed within the Davidson Evaporite.

A 4m-thick, soft shale formation forms the lowermost unit of the Dawson bay formation. It includes approximately 30m of limestone. Collapse structures in the deposit area are found in localised areas where the original geological layering has been considerably or completely destroyed. Ranging in size from a few hundred metres to tens of kilometres, these structures extend from the surface until the Prairie Evaporite horizons.

In the main potash bearing zone, the lowermost lower salt unit is overlain by another unit of three-potash bearing units known as the Esterhazy Member, Belle Plaine Member and the Patience Lake Member, as well as one marker bed known as White Bear Marker Bed.

Sylvinite-hosted beds within these members contain a combination of sylvite, halite, trace amounts of carnallite and water-insoluble minerals, including clay, anhydrite, and dolomite. Together, this mixture composes the sylvinite rock.

Reserves of the Jansen mine

The Jansen mine is estimated to contain 5.23 billion tonnes of measured resources grading 25.6% potassium oxide (K₂O), and 1.28 billion tonnes of inferred resources grading 25.6% of K₂O, as of June 2021. The probable reserves at the project are estimated at 1.07 billion tonnes, grading 24.9% K₂O.

Mining and processing at the potash project

Mining will involve the long room and pillar method. The potash-bearing members will be accessed through a production and service shaft that will be sunk 1km from the surface. BHP Billiton initiated drilling for the ground freezing process, required to sink the shaft.

Several rooms will be cut into the potash-bearing zones, leaving several pillars to hold the mine roof. As mining proceeds, a grid-type pattern of rooms and pillars will be created. The ore will be mined using large borers. Through conveyors, the mined ore will be brought to the production shaft that will hoist it to the surface. Approximately 24Mt of ore will be hoisted to the surface at peak capacity.

During processing, the ore will be crushed to separate the potassium chloride and sodium chloride crystals. The final saleable product will be produced following the stages of scrubbing, conditioning, flotation, and de-brining.

The tailings including salt and clay will be stored and managed on the surface separately. Surplus brine from the Tailings Management Area will be returned to a geological unit named Deadwood formation, which is hosted 1km below the surface. Approximately one million cubic metres of water a year will be used by the process plant.

Contractors of the Jansen Potash project

The contract to construct two mine shafts at the Jansen Potash project was awarded to DMC Mining in December 2010. The five-year contract is valued at $400m.

A joint venture between Canadian companies Hatch and Bantrel was awarded a contract to provide engineering, procurement, and construction management (EPCM) services for the project in 2017.

BHP Canada signed a conditional agreement with Westshore Terminals for port services for the Jansen mine. Westshore is responsible for handling potash for BHP until 2051. It will also build the port infrastructure to handle potash at the Roberts Bank Terminal in Delta by 2026.