Stonehenge Tunnel | National Highways must justify why alternatives were ruled out

It comes after local councils and transport groups complained that it was “not clear” how National Highways had ruled out alternative options.

The current plans are for a 12.8km dual carriageway, and a 3.2km tunnel underneath the world heritage site (WHS) closely following the existing A303 route alignment.

Opponents of the scheme have suggested that a longer tunnel would help avoid damaging the historic site.

However in documents submitted to the Planning Inspectorate January, National Highways said its position regarding a bored tunnel extension "remains unchanged" and "this option should be excluded from further development".

The roads operator added: "There is no evidence that the additional investment required to extend the tunnel length would deliver meaningful additional benefits to the World Heritage Site (WHS) that would justify the additional cost."

National Highways has also ruled out a series of other alternatives, including a cut and cover tunnel extension which was due to the "significant additional cost".

National Highways also ruled out alternative routes to the south of the WHS due to their "much larger footprint" and "greater overall environmental impact than the partially tunnelled options". Meanwhile, a proposed new route to the south of Salisbury was ruled out over increased habitat loss and a new proposed route north of the WHS was rejected "on the basis of the harm it would cause to the setting of the WHS and key assets within it".

Transport secretary Grant Shapps is currently in the process of “re-determining” his decision on National Highways’ planning application after a High Court judge ruled his original decision to approve the scheme as “unlawful”.

As part of the process, Shapps must prove that he has considered the environmental and carbon impact of the proposed scheme in relation to government commitments and legislation, as well as providing evidence that alternative schemes have been adequately considered.

Consequently, Shapps has asked National Highways to provide greater detail on why it has ruled out alternative routes.

A letter sent this week adds: “A number of consultees have raised the issue that it is not clear how the Applicant has arrived at the conclusion that the alternative tunnel routes would only have minimal additional heritage benefits over the Development. The Applicant is asked to explain fully the basis on which they reached this conclusion.”

It continues: “The explanation should include full detail of reasoning, the matters considered and any methodology that was used and, where applicable, be cross-referenced to the examination material or subsequent information provided to the Secretary of State.”

Shapps has also requested further information around the scheme's impact on four newly identified heritage assets at the site, as well as “issues relating to adverse impacts of tunnelling through chalk bedrock”. National Highways has until 27 June to respond to the DfT.

Last month, National Highways selected a joint venture comprising Spain’s FCC Construcción, Italian firm WeBuild and BeMo Tunnelling from Austria to deliver the £1.25bn contract for the tunnel, along with the main construction work for the A303 Amesbury to Berwick Down scheme past Stonehenge.

The JV will be supported by a design consortium made up of Atkins, Jacobs and Spanish designer Sener acting as the design joint venture.

The contract is subject to final sign-off on the £1.7bn scheme by Shapps.

Mace has also been appointed as the complex infrastructure programme (CIP) commercial partner on the delivery of the scheme. Mace’s work will involve delivering commercial services including cost consultancy and quantity surveying, as well as acting as a liaison between National Highways and its main contractors.

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