A £47M extension to a tunnel running through the Chiltern Hills north-west of London was among the final recommendations of MPs hearing evidence on the route for phase one of High Speed 2.
The cross-party High Speed Rail (London to West Midlands) Bill Select Committee approved the 2.6km extension of the tunnel, which was initially proposed to run for 13.4km north from the M25.
The chosen extension, to South Heath, was put forward by project promoter HS2 Ltd against a resident group proposal for a 4.1km extension to Leather Lane. Options discarded earlier by the committee included total tunnel lengths of 29km and 23.9km.
“We favoured the South Heath extension option and directed an additional provision to implement it,” said the committee report.
“We took into account the benefits for Mantles Wood, the overall benefit to the area of outstanding natural beauty, the reduction in requirement for agricultural land, and the significantly reduced construction noise impact on South Heath.
“We heard that the Leather Lane extension would cost of the order of £40M on top of the South Heath option. We were not convinced that there would be significant environmental benefit. Our view was that it was not justified.”
The committee spent two years hearing petitions from those specially and directly affected by the bill, which effectively forms the planning permission for the first leg of the mega project.
Other directions from the MPs included greater noise protection for Wendover, better construction arrangements in Hillingdon, a remodelled maintenance depot at Washwood Heath as well as a call for a “coherent approach” to the redevelopment of Euston.
“Our work on Phase One, we believe, helps to add substantial environmental, social and design benefits to the scheme, commensurate with good use of public money and a viable engineering design,” said the report.
Transport secretary Patrick McLoughlin will respond to the recommendations in due course.
HS2 chairman David Higgins this month set out plans to use the £56bn scheme to “transform” the infrastructure industry.