North Yorkshire potash mine developer Sirius Minerals has named the Hochtief Murphy joint venture as the preferred bidder for major tunnelling work on the scheme.
Construction of the 37km, 6m diameter mineral transport system tunnel is expected to be undertaken using tunnel boring machines (TBMs) and will take five years to complete.
The tunnel, designed by Arup, is set to be bored by five hard rock TBMs working at multiple faces through sinking of four intermediary shafts. The deepest point of the tunnel is expected to be 360m below ground level.
Murphy Hochtief, as well as the unsuccessful bidders, have been involved in a competitive tendering process for the work over a 19 month period.
Sirius Minerals has also announced that Thyssen and Redpath are the preferred bidders for shaft sinking operations on the project.
Sirius has said that the first 12 month phase of work will form front end engineering design with detailed geotechnical investigation, which is expected to refine estimates for the work ahead of agreement of the contract sum.
Contracts for the work are expected to be formally awarded once the project to mine polyhalite for fertiliser production at the site secures the necessary funding.