TUNNELS – WHAT DO WE KNOW?
Tunnel Reports – (8/1/2015) – new research supports that the Colne Valley route should be tunnelled.
Late November 2013 – the government has released it’s decision on compensation/assurances for tunnelled areas – HS2 has not bothered to contact us to let us know but we found this link here.
HS2 Ltd promised in 2012 to release information on tunnelling. In October 2013 they have finally released reports that can be found on their website here.
The non-technical summary pdf can be downloaded by clicking here.
Although our campaign’s stance is STOP HS2 it is important that we understand the impacts of the proposed route within each community/area. Ruislip will now have a 2.7 mile twin bored tunnel (as originally recommended by HS2 engineers but ruled out by the previous Secretary of State Philip Hammond) from Northolt to West Ruislip.
The tunnel will run under the Chiltern Line for the majority of the route but in places will run under homes, gardens, green spaces and businesses. There will also be a large tunnel ventilation shaft constructed in Ruislip, probably on brownfield land near the old Express Dairy site. The short length of the tunnel will exacerbate concerns in West Ruislip and Ickenham where there will be a tunnel portal. Peer reviewed evidence clearly indicates louder noise when trains exit tunnel portals.
Construction risks: Government will state a low risk to residents as the tunnel is bored. However, the experience of High Speed 1 showed that unpredicted tunnel collapse can and does occur, with residents of Stratford very fortunate not to be injured during two documented collapses.
Construction costs: It is well documented that HS1 became the most expensive railway largely because of the cost of tunnels in London. It is also known that government aims to reduce construction costs to enhance the business case and limit the number of tunnels this time. This will not be acceptable and appropriate mitigation will be fought for in West Ruislip and Ickenham regardless of costs. If the fanciful forecasts and predicted benefits have any credibility, then the maximum environmental mitigation is affordable.
The previous documented cost of providing a tunnel through Ruislip was put at £350m more than the route consulted upon last year. Recent reports in the press suggesting a cost of only £50m more appears highly dubious and raises questions about what level of destruction/loss of homes was really anticipated by government. At a presumed additional construction cost of £350m for the Ruislip section, an additional length of tunnel extending beyond Ickenham communities should be expected to cost a similar amount per kilometre or less (with economies of scale).
It is critical that concerned residents continue to write to their MPs about these issues. these are some questions you might want to ask them to ask the Secretary of State:
Please provide specific and substantiated evidence as to the effects of tunnelling.
By way of example, what caused gardens to cave in during the construction of HS1?
Please provide details as to the nature and extent of the assessments to be made of the buildings and foundations in our area
Please provide details as to which buildings will qualify for assessment ie directly over tunnels and within what radius of the tunnels?
Can the tunnel be pushed deeper to a consistent depth of between 40 – 50m? If no, please provide specific evidence as to why not.