The tunnel will be constructed using two tunnel boring machines (TBMs) deployed from Wilton and Woodsmith Mine. The original plan to use a third machine from Lockwood Beck was altered in November 2019, after the Wilton machine's high rate of progress made it no longer necessary.
The vertical alignment of the tunnel will be located within the low permeability Redcar Mudstone strata. Geotechnical conditions along the route have been assessed from a combination of existing geological knowledge, surface mapping, existing geophysical surveys and 12 boreholes along the length of the route. The selected route avoids shallow aquifers and any abandoned iron stone mines in the Esk Valley and Guisborough areas.
The TBM at Wilton is assembled in a shallow portal on the Mineral Handling Facility (MHF) site. It arrived on Teesside in February 2019 - read more about it, or watch the video of its journey across Europe, below.
The TBM starting at the mine site will require a shaft to be constructed, down which the TBM components will be lowered and assembled in a cavern at the bottom, before tunnelling commences.