Highways Agency

A303 at Stonehenge

Review of English Heritage 2km Tunnel and Comparative Options ("The Halcrow Report")

June 1998

 

 
 
 

Executive summary

Extensive studies were carried out by Sir William Halcrow & Partners (Halcrow) on behalf of the Highways Agency between 1991 and 1996 into options for improving the A303 between Amesbury and Berwick Down including the section past Stonehenge. A public consultation was held in 1993 and a planning conference in 1995. The conference supported in principle a long tunnel under the Stonehenge site, but recognised the difficulty of funding such a scheme from the roads programme. The Stonehenge section was withdrawn from the roads programme in 1996.

In relation to a meeting between ministers from the Department Of Culture, Media And Sport (DCMS) and the Department of the Environment Transport and the Regions (DETR) in November 1997 English Heritage prepared a scheme for a two km on-line cut and cover tunnel.

Halcrow were commissioned by the Highways Agency to review this proposal and other comparative options based on options considered by the 1995 conference. The review was to be carried out in accordance with a study remit prepared by DETR and agreed with DCMS and English Heritage.

The review was carried out on the basis of the New Appraisal Framework prepared by DETR for the current Roads Review. This aims to assess schemes against the five criteria establish by the Government for the Roads Review:

• Integration
• Accessibility
• Safety
• Economy
• Environmental impact

The work was initially carried out in line with guidelines prepared in November 1997. The appraisal was later reviewed, and the results updated where necessary, in accordance with later guidance issued following comments from Statutory Advisors.

The review considered four main options:

• Option 1: English Heritage On-line 2 km cut and cover tunnel
• Option 2: On-line 500 m tunnel
• Option 3: Representative Southern Route
• Option 4: Representative Northern Route

The results of the appraisal are summarised for the five criteria for the Roads Review on 'single page summaries' for each of the four options.

The review also considered two short term solutions, widening to three lanes within the existing highway boundary and a 'temporary' widening supported on a geotextile membrance (as proposed by Wiltshire County Council). Junction requirements at Countess Roundabout and Longbarrow Crossroads were also considered. The programme to scheme implementation was also examined.

The principal conclusions of this review were as follows:
 

English Heritage 2 km on-line tunnel (option 1)

• The English Heritage 2km on-line tunnel provides significant benefits to the setting of Stonehenge within the World Heritage Site. Any additional impact would be in the vicinity of the existing road. It removes the road from sight weithin the Stinehenge Amphitheatre but not the Stonehenge Bowl. The scheme is seen as a major compromise by English Heritage and the National Trust.
• The total construction cost of the 2km tunnel option is estimated at £105.9 (Q4, 1997) (£125.2 million including land, rescue archaeology, preparation and supervision). Both figures exclude VAT. These costs include Winterbourne Stoke bypasses, but exclude Countess roundabout grade separation (previously considered as a separate regional scheme). This gives a BCR in the order of 1.3, which is the normal minimum factor before a scheme is considered. However, given the competition for inclusion in the Roads Programme, where other schemes will have higher BCRs, additional funds for the English Heritage scheme may be required from other sources to enhance the economic case. A reduction in the tunnel length whilst maintaining the majority of the benefits could also be considered.
• The 2km tunnel has been proposed by English Heritage and has National Trust support in principle. This should make the scheme deliverable subject to clearance through the National trust Council (the scheme affects inalienable land) although it is likely that there would still be some opposition from interested parties.

500m on-line tunnel (option 2)

• The 500m on-line tunnel provides limited benefit to the immediate setting of Stonehenge by providing some unity with the Normanton Down barrow group. However, there would still be significant impacts within the World Heritage Site. The road would still be visible within both the Stonehenge Amphiteatre and the Stonehenge Bowl, but would enable motorists to retain a view of the Stonehenge monument.
• The total construction cost of the 500m tunnel option is estimated as £68.4 million (Q4, 1997) (£82.4 million on the same basis as above) including Winterbourne Stoke bypass, but excluding Countess roundabout grade separation. This gives a BCR of 2.09.
• This option is now opposed by English Heritage and the National Trust and would be difficult to deliver. This option was withdrawn by the Roads Minister in 1994 following opposition at a conference hosted by English Heritage.

Representative Southern Route (option 3)

• The Representative Southern Route provides significant benefits to the setting of Stonehenge within the World Heritage Site. It removes the road from site within the Stonehenge Amphitheatre but not the Stonehenge Bowl. It introduces significant new impacts into a previously unaffected area of the World Heritage Site, which is also good quality landscape.
• The total construction cost of the Representative Southern Route is estimated as £58.8 million (Q4, 1997) (£70.0 million on the same basis as above) including Winterbourne Stoke bypass, but excluding Countess roundabout grade separation. This gives a BCR of 2.35. However, this includes crossing National Trust inalienable land on the surface. If a cut and cover tunnel were provided under this land it would increase the cost by about £45 milliion and reduce the BCR to about 1.25
• The option does not have English Heritage or National Trust support and is strongly opposed by local landowners. It would be difficult to deliver. This option was withdrawn by the Roads Minister in 1994 following opposition at a conference hosted by English Heritage.

Representative Northern Route (option 4)

• The Representative Northern Route provides significant benefits to the setting of Stonehenge. it removes the road from site within the Stonehenge Amphitheatre but not the Stonehenge Bowl. It introduces significant new impacts into a previously less affected area of the World Heritage Site. It also moves the road close to the local communities around Larkhill and is close to the MoD Artillery Ranges. Tunnels were previously considered (in response to concerns of English Heritage and MoD) in mitigation of the impacts of this route. In the Highways Agency and consultant's judgement there were no real benefits north of Fargo Plantation and they were more marginal adjacent to Strangeways. These are not included in the scheme costs.
• The total construction cost of the Representative Northern Route is estimated as £58.3 million (Q4, 1997) (£70.4 million on the same basis as above) for the full length between Amesbury and Berwick Down, but excluding Countess Roundabout grade separation. This gives a BCR of 2.04.
• The option does not have English Heritage or National Trust support. It is also now likely to be opposed by the MoD (although at one time supported) and strongly opposed by local communities. It would be very difficult to deliver.

'Short term' solutions

• Short term widening to three lanes within the existing highway boundaries is possible but offers few demonstrable benefits.
• The 'reversible' geotextile option proposed by Wiltshire County Council is not reversible as proposed. Although it could probably be made reversible it is unlikely to be truly reversible. Furthermore there are legal problems over its provision and future removal. In English Heritage's view this option would still require a long term solution.

Junctions

• If dualling is carried out past Stonehenge, it may also be desirable to provide grade separation at Countess Roundabout. This would add £5.2 million (Q4, 1997) to any costs. When assessed separately the BCR of such grade separation is 4.5. if this work were carried out as part of an overall scheme the BCRs of the options would increase as follows:
  • Option 1: 1.40
  • Option 2: 2.24
  • Option 3: 2.51
  • Option 4: 2.22
• A possible grade separated roundabout at Longbarrow crossroads could accommodate any additional turning traffic resulting from any relocation of the Visitors centre. English Heritage have expressed reservations about grade separation at this junction. Solutions would need to take account of short and long term traffic needs and would be subject to detailed designs following consultation and further environmental assessment.
• If a grade separated junction is not provided at Longbarrow crossroads there would be additional delays and accidents for through traffic on the A303. Additional turning traffic for the Visitors Centre would bring forward the time when over-capacity occurred. HA NCS may require grade separation to be provided.

Programme

• The provisional estimate of the period from the Preferred Route Announcement to completion of construction is between 8 and 10 years.

Overall summary

This report has considered the latest proposal by English Heritage for a 2km cut and cover tunnel for the A303 past Stonehenge, other tunnel options, the options considered at the 1995 planning conference, geo textile and short turn measures in accordance with the study remit, including strategic issues.

The findings are that a 2km cut and cover tunnel is technically feasible, and in combination with a Winterbourne Stoke bypass would cost in excess of £100m; (in excess of £120m including works, land, archaeology, preparation and supervision). Both figures exclude VAT.

Its is likely to take between five (being very optimistic) and seven years from roads review (if successful) 2 start of construction, and between 8 and ten years to completion.

Its benefit to cost ratio, assuming opening in 2008,is in the order of 1.3,and is likely to need Treasury clearance because it is an unusual project of marginal economic benefit on transport grounds.

It is the most expensive of the options considered, but is the only one which now has for support of English Heritage and the National Trust, and is likely to achieve a general measure of support from most (but not necessarily all) main interests including the local community. This will need to be checked at public consultation for the scheme.

The 1995 conference routes (options 2, 3 and 4) in many areas offered comparable benefits, but suffered by being close to the Larkhill community in the north, or through National Trust land to the South. They are identified as difficult to achieve. They are now strongly opposed by English Heritage, the National Trust and, in the case of option 4 by some of the MoD (MoD supported in concept at ministerial level in 1995), as well as local landowners.

All of the options, unavoidably cross the World Heritage Site, and no other suitable solution has been found. All three routes offered major benefit to the setting of Stonehenge, but the on-like solution has less effect on the World Heritage Site.

In strategic terms the role of the A303 may be subject to be findings of an integrated transport study. If such study supports completion of dual carriageway for the main part of A303, dualling including the use of the cut and cover tunnel as suggested is likely to be more robust and offers appreciable transport and heritage benefit.

In the absence of such policy, it is doubtful whether tunnelling as suggested could be justified in transport terms. The scheme has a BCR in the order of 1.3 the normal minimum factor before a scheme is considered. However, given the competition for inclusion in the roads programme, where other schemes will have higher BCRs, an additional contribution from heritage and environmental funds may be required to enhance the economic case.

If taken forward to detailed design further assessment of risk and value management would be needed to test the solution. Final decisions on the form of junction at Countess roundabout and Longbarrow crossroads would be needed at detailed design stage.

The cut and cover tunnel solution offered by English Heritage is a major compromise as seen by the cultural heritage interests, and offers transport as well as cultural benefit, albeit at highest cost. It is the only scheme reviewed which has a realistic prospect in English Heritage's view of delivering the proposed improvements to be A303 at Stonehenge within the foreseeable future.
 
 

Sir William Halcrow & Partners

in association with

Halcrow Fox
The Cooper Partnership
John Samuels