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Tunnelling on £4.2bn polyhalite mine moves step closer

The first of three 1,800t tunnel boring machines (TBMs) for the longest mineral transport system in the UK is almost ready for operation.  

The 225m long machine is currently undergoing final checks at a factory in Germany. It will then be disassembled and shipped to the Sirius polyhalite mine in Yorkshire.

The single-shield TBM will be operated by contractor Strabag, with work due to start in the second quarter of 2019 after the TBM is fully reassembled on site 360m below ground.  

This TBM will bore the first of three tunnel drives making up the 37km tunnel that will house the longest conveyor system in the UK, capable of moving 20M.t of polyhalite a year under the North York Moors. 

The tunnel system was selected to minimise the impact of moving polyhalite out of the mine. A cut and cover tunnel system has previously been rejected on environmental impact grounds.   

The conveyor will carry the polyhalite – a fertiliser –  from a mine near Whitby to a processing plant at Wilton near Teesside Harbour. 

Sirius minerals   project overview

Sirius minerals project overview

Construction of the 37km, 6m diameter mineral transport system tunnel is expected to be undertaken using tunnel boring machines

 Chris Fraser is managing director and chief executive of client, minerals company Sirius. He said the project had hit a major milestone and that it would continue to be a source of jobs for the local area. 

“The assembly of our first tunnel boring machine represents an exciting milestone for the company and the region,” he said. 

“With around 1,000 people currently employed across all of our sites, the team working to make this project a success continues to grow as we deliver this world class project.  We expect to create hundreds more skilled construction roles in the coming months to help build our mineshafts, tunnel and mineral handling facility.” 

The costs of the project have risen dramatically from £858M to £1.46bn following changes to the tunnel design. This involved increasing the tunnel’s internal diameter of the tunnel from 4.3m to 4.9m and increasing the lining thickness from 250mm to 350mm. 

Two other machines are planned to be launched in 2020 from Whitby and Lockwood Beck, near Guisborough, to complete the remaining 24km of tunnel. 

Sirius expect to reach the polyhalite seam in 2021 and to be producing 10M.t of fertiliser per annum by 2024, creating around 1,000 long-term operational jobs. 

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