What's next?
The next step in the process is for the various recommendations made by the Select Committee to be debated in the House of Lords. The approved bill, if amended will then return to the House of Commons for final approval. It is anticipated that this will not be a long process, and the Bill should receive Royal Assent by early March. When it is approved, the detailed design stage of the infrastructure will begin.
The Chiltern Society has identified one item, which gives us great concern. This relates to the operational safety of the two-bore tunnel design. The Business Case relies on a maximum of 18 trains per hour each way travelling at 320kph. In the event of a breakdown in a tunnel, 1,100 people will need to disembark the train on a platform 1.3m wide, and be moved from the incident tunnel, through cross passages 350m apart, to the other tunnel where they will need to stand on a platform 1.3m wide until a train can be organized to collect them. Currently there is no control system developed to stop the trains on the other track entering the tunnel where the passengers will have to wait. We have raised this issue with HS2, The Transport Select Committee, the Treasury Committee, the HoL Economic Affairs Committee, the Secretary of State for Transport and the Chancellor. We await their responses.
HS2 have commenced ground investigation work in a number of areas to understand the ground conditions that they will be tunneling through. This has involved work at a number of sites in The Chilterns. In discussions with HS2, it has become clear that adverse ground conditions could result in a change in the detailed design. An example of this relates to Chalfont St Giles, where the tunnel is only 19m below the ground surface. Of that 19m, 16m is rubble chalk, with the potential for settlement. It was suggested that the tunnel should be at least 10m lower. HS2 explained that this would require an extension of the tunnel by approximately 1km. The ground condition reports are apparently due in March.