The potential engineering challenges and associated cost of building High Speed 2 (HS2) over salt marshes in Cheshire has once again been highlighted by MPs in the House of Commons.
The MPs from areas affected by the line said they were were worried and angry with a claimed lack of communication from the rail body behind the line. The concerns were raised in a debate in the Commons on Wednesday afternoon.
Principally, MPs fear spiralling costs due to the complexities of building over the land and future problems with subsidence when the line passes over the area riddled with old salt mines.
Conservative MP for Eddisbury Antoinette Sandbach said a “deep worry” was that HS2 did not seem to be disclosing the “appropriate” level of technical reports which would allow experts to give their opinion on the scheme.
She said one such expert had written to the transport secretary 18 months ago to emphasise that ground-level surveys should be started now, to allow HS2 to identify subsidence and problem areas.
The discussion also referenced a report commissioned by HS2 opposition group Mid Cheshire against HS2 and written by consultant TerraConsult, which said building foundations for viaducts would face considerable technological challenges and piles could be up to 100m long.
Sandbach said the report was not referenced, following consultations, in the Decision Document when the new alignment was announced in July of this year.
The part of the phase 2b route in question is a 20.2km long section which runs from a tunnel portal north of Crewe to Arley Brook north east of Northwich. It is a contentious section of the route which was moved to its current alignment after initially passing through gas reserves nearby.
In response, rail minister Paul Maynard said HS2 had commissioned a specialist mining engineer to undertake a study into the section of the route. The study is being carried out in consultation with the Cheshire Brine Subsidence Compensation Board, using existing data from organisations such as the British Geological Survey, the salt industry and local authorities.
Maynard said the TerraConsult report was taken into account both before the November 2016 announcement, and before the more recent one July. He added a meeting between the opposition group, TerraConsult and HS2 Ltd would take place next week to explain its reasons for the current alignment between Middlewich and Pickmere.
The minister acknowledged the area was a “sensitive and complex” section of the route and more work was needed to “further assess geological risks and to provide suitable mitigations for them”.
“HS2 Ltd plans to carry out early geotechnical investigation work in the mid-Cheshire area to gather more advanced survey information,” he said. “We will continue to work with my hon. Friend to try to ensure that the best mitigation possible occurs.”