Question to the Department for Transport:

To ask the Secretary of State for Transport, what assessment her Department has made of the potential merits of the use of Norwegian-style drill-and-blast tunnelling methods in the construction of UK transport tunnels; and whether she has considered the use of a Private Bill procedure for the authorisation and delivery of tunnel construction projects.

Norwegian style drill and blast tunnelling is generally suited to continuous hardrock geology that is not characteristic of most interurban routes in the UK. Instead, the latter frequently involves tunnelling through highly variable ground conditions including clay, weak, weathered or fractured rock and sands and gravels submerged in high-pressure ground water. Modern tunnelboring machines (TBMs) are able to cope with such variable geology and prevent the excavation face of the tunnel catastrophically collapsing before the tunnel is lined with concrete.

That said, the choice of tunnelling method will depend very much on local ground conditions for each major road or rail project. TBMs are frequently tailor-made to suit those ground conditions. The department would always look to tunnelling experts to recommend the most cost-effective method for a particular tunnel and we would not rule out drill-and-blast if it was through suitable rock.

For most tunnelling projects existing statutory consenting routes remain available, and the use of a Private Bill would only be considered where there is a specific and compelling justification.