THE NATIONAL TRUST will this month decide whether to push for a £30M extension of the proposed A3 Hindhead tunnel on environmental grounds.
The 1.7km tunnel is the key part of a 6.7km road scheme to eliminate a bottleneck on the A3 London to Portsmouth road at the Devil's Punch Bowl in Surrey (GE June 2004).
The trust supports the scheme in principle but is concerned about the impact of the southern portals on an area called Tyndall's Wood.
Much of the area around the Devil's Punchbowl, including Tyndall's Wood, is owned inalienably by the National Trust. This means it cannot be forced to sell the land for development, even if the scheme gets the goahead after the public inquiry starting in September.
At present, the road will emerge from the tunnel halfway across Tyndall's Wood, crossing the rest of the wood on an 11m to 12m high embankment. It then swings west through woodland in a cutting up to 18m deep, emerging to cross the Hazel Grove junction - a very constrained location, with schools and housing close by.
An alternative scheme was due to be formally issued as GE went to press.
Developed by design and build contractor Balfour Beatty and its consultant Mott MacDonald, it would see a 200m cut and cover tunnel formed on top of the embankment, followed by a 130m long bored section instead of the cutting.
This bored section will be only 10m below ground in places, requiring delicate tunnelling.
It is estimated that extending the tunnel could add £30M to the £145M cost of the scheme.