n firms were consulted by the Department
of Transport (Wainwright, interview 24/2/99). In the words of the recent
editorial in Antiquity, the cost of the cut-and-cover tunnel has been
'plucked for discussion' (Anon 1998: 733). Lord Kennet's claim that a
3.2 km. single bore, two-track rail tunnel is being driven through North
Downs for £80 million (Kennet 1998: 736) appears however to disregard
infrastructural costs (Wainwright, interview 24/2/99). Neither the technical
specifications of the proposed deep bore tunnel, nor the geotechnical
survey on which the costing of a deep bore tunnel was based have been
published, but they would have to be made available at a public enquiry.
It has been suggested that additional funding could be sought from European
or international sources (Fielden 1998: 736). The suggestion that 'heritage
sources' should bear part of the cost contradicts, however, the 'polluter
pays' principle (Stone n.d.: 4). Indeed, enquiries made by the Wiltshire
Archaeological Society have ascertained that even if alternative sources
of funding were available, the cut-and-cover tunnel would still be the
preferred option of English Heritage (Fielden, interview 13/4/99).
One of us (RL) spoke to a qualified, professional civil
engineer who stated that the principal cost of a deep bore tunnel is setting
up the equipment, while the cost of a cut and cover tunnel is directly
related to its length. In general terms, a short (half-kilometre) deep
bore tunnel would be six times more expensive, a 2.5 kilometre deep bore
tunnel 35% more expensive than a cut and cover, but a four kilometre tunnel
only 10% more expensive. If the two kilometre cut and cover tunnel costs
£125 million, a four kilometre deep bore tunnel would cost £275
million. The new technique of spraying concrete onto the walls of the
bore is still viable. The recent collapse of the tunnel under construction
at Heathrow Airport was caused by the thinness of the sprayed concrete,
not an inherent defect in the method.
Wainwright reports that the 'green' route planned for the
deep bore tunnel would in fact only include 2.8 km. of deep bore. The
remainder of the route would be constructed by cut-and-cover in an area
where archaeological sites are more dense than on the route of the proposed
cut-and-cover tunnel (Wainwright, interview 24/2/99). The civil engineer
consulted confirms that the first 750 metres at either end of a deep bore
tunnel are usually cut and cover.
A longer tunnel following the present route of the A303.
Although the original ('green route') long tunnel was envisaged as passing
under the Avenue and Cursus, a deep bore tunnel starting further east
could follow the present route of the A303. After crossing the eastern
boundary of the World heritage site, the A303 passes through a cutting.
If the tunnel started within this cutting, it could pass further beneath
the surface of Stonebarrow Bottom, eliminating the covering embankment.
The line of the prehistoric feature, the Avenue, could then also be restored.
A four kilometre tunnel would push the start of the approach cuttings
back to the borders of the World Heritage site, but would not place them
outside the site. A longer tunnel would require above-ground ventilation
shafts (Master plan 1998: 4). The civil engineer consulted confirms that
any tunnel more than 2.5 kilometres long would require above-ground ventilators.
A four-kilometre tunnel would probably require three, each consisting
of a single-storey building. Brian Davidson suggests it would be in keeping
with a 250 year tradition to conceal such ventilators behind small tree
plantations (interview 15/3/99).
The position of the National Trust
No tunnel can be constructed without the agreement of the membership of
the National Trust. The 2.5 million members have not yet been consulted.
Land which the National Trust holds inalienably will have to be surrendered
to allow construction (Peter Fowler, interview 17/3/99). As noted above,
the Director General of the National Trust said in 1994 that the long-bore
tunnel was the only feasible alte