Tuesday 7 March 2017

UNESCO Astronomer Experts Response to the Stonehenge Tunnel Proposal

A response from the co-authors of the extended case study on Stonehenge on the UNESCO–IAU Portal to the Heritage of Astronomy - Dr. Amanda Chadburn and Prof. Clive Ruggles

1. To what extent do you agree with our proposed option?
Strongly disagree
Please provide any comments to support your answer for question 1:
We are responding as archaeologists and co-authors of The Extended Case Study on Stonehenge [ECS15]. This response reflects the personal views of the
authors and not necessarily those of their employers or of the International Astronomical Union who published ECS15, and who work alongside UNESCO to
implement the Astronomy and World Heritage Thematic Initiative.
In this response, we are only considering the archaeoastronomical aspects of Stonehenge, and not the other attributes of Outstanding Universal Value (OUV) nor
any other designations and their settings such as Registered Parks and Gardens, Listed Buildings, Scheduled Monuments which are not of OUV, SSSIs and so
on. Of course, we believe that all such designations, places of significance and attributes of OUV should be systematically and fully assessed and taken into
account, but here we concentrate on Attribute 4 of OUV (see below), which is the subject of ECS15 (see bibliography). The public consultation documents contain
no evidence that this issue has been addressed or taken into account.
Clive Ruggles is also a member of a consortium of 21 "Stonehenge experts" who have submitted a broader archaeological view.
See section 7 for reasons why we disagree with the proposed option.
Key features of the proposed option
2. To what extent do you agree with our proposed location of the eastern portal?
Tend to agree
Please provide any comments to support your answer for question 2:
The eastern portal does not directly raise any astronomical concerns. We agree that it is preferable to place the portal to the eastern side of the line of the
Stonehenge Avenue, the processional approach to Stonehenge, whose final approach is along the solstitial axis.
3. To what extent do you agree with our proposed location of the western portal?
Strongly disagree
Please provide any comments to support your answer for question 3:
See section 7 for full reasons.
4. Of the two possible routes for the Winterbourne Stoke bypass which do you consider is the best route?
No preference
Please provide any comments to support your answer for Question 4:
We disagree with the location of the western portal so cannot agree with either consultative route, so "no preference" is our only option, although "neither" would
be more accurate. Additionally both routes run along the solstitial axis for a distance. See section 7 for full reasons.
5. What are the most important issues for you as we develop our proposals for the A303/A345 Countess junction?
To preserve as dark a night sky as possible.
6. What are the most important issues for you as we develop our proposals for the A303/A360 Longbarrow junction?
Option 1S has the junction at almost the exact spot where the midwinter solstice sun would set – the very spot critical to the design and use of Stonehenge, and
therefore critical to its understanding and significance. This would be highly damaging and should be avoided.
7. Do you have any other comments?
Since 2008, various sightlines within the Stonehenge World Heritage Site (WHS) have been formally recognized as carrying attributes of the Outstanding
Universal Value (OUV) that qualifies the area for World Heritage status [MP09, pp 26-7]. The sightline to the SW at Stonehenge itself, being the principal direction
faced by the monument, is indisputably the most important of all of them. The approach to the monument has only recently been restored, following the removal
of the A344 road in 2013, allowing visitors once more to approach the monument along the intended formal route (the Stonehenge Avenue) from the NE, facing
the direction of winter solstice sunset. This helps considerably to strengthen visitors’ appreciation of the importance of the view straight ahead through the
monument at the final point of approach.
The 2009 and 2015 Management Plans list the seven attributes that express the OUV of the Stonehenge World Heritage Site [MP09, p. 28; MP15, p. 32]. 1
Attribute 4 is “The design of Neolithic and Bronze Age funerary and ceremonial sites and monuments in relation to the skies and astronomy”.
The significance of the solstitial axis at Stonehenge is recognized explicitly in the Statement of Significance agreed by UNESCO’s World Heritage Committee in
2008 (see [MP09, pp. 26–27]) as well as in the Statement of Authenticity that forms part of the revised Statement of OUV submitted to UNESCO in 2011 (and
formally adopted in 2013) [MP15, p. 28]. “An outstanding example [of a highly organised prehistoric society able to impose its concept upon the environment] is
the alignment of the Stonehenge Avenue ... and Stonehenge stone circle on the axis of the midsummer sunrise and midwinter sunset” [MP09, p. 27].
Preserving the integrity of the solstitial sightlines in the Stonehenge WHS is a major theme of an extended case study included in the second ICOMOS–IAU
Thematic Study on astronomical heritage. This case study [ECS15] which we co-authored was one of a set presented at a side event at the 2015 UNESCO World
Heritage Committee (39COM) in July 2015, and was published in March 2016 on the UNESCO-IAU Portal to the Heritage of Astronomy. The whole volume is due
for hard copy publication in time for presentation at the next World Heritage Committee (41COM) in July 2017. The case study is on-line and additionally has
been widely disseminated within the UK and internationally, for example at the Avebury and Stonehenge Archaeological and Historical Research Group
(ASAHRG) in Jan 2015, at the European Association of Archaeologists annual conference in Sept 2015, and at a public workshop on Science and Technology at
Stonehenge held at the Politecnico Milano in May 2016.
The need to preserve (and, where possible, to restore) the integrity of the sightlines is recognized in the 2015 Management Plan. Policy 3c [MP15, p. 105] is to
“Maintain and enhance the setting of monuments and sites in the landscape and their interrelationships and astronomical alignments with particular attention
given to achieving an appropriate landscape setting for the monuments and the WHS itself”. Action 31, already undertaken by us (see [ECS15]), is to “identify key
views between the attributes of OUV and both into and out of the WHS [and] identify key astronomical alignments”. Strategies for implementation include:
• Improving and restoring ridges and horizons within the sightlines by removing visual obstacles such as buildings and trees;
• Avoiding new planting that, when fully grown, could obscure the sightlines; and
• Defining a buffer zone that includes the sightline corridors extending beyond the WHS. Fountains Abbey WHS (see [ECS15, fig. 8]) provides a precedent.
The need to assess and preserve views to and from historic assets – and this view is an example of the highest significance (OUV) - is well understood and
guidance on how to do this is readily available [SHV11] [GPA3].
Under these proposals, the western entrance of the tunnel lies almost exactly on the winter solstice sunset alignment. There are two options for the route of the
emerging dual-carriageway approach road to/from the west. In both routes, the road broadly follows the solstitial alignment for a distance, but then the options
diverge as one heads west. In Option 1S, the southern option, the road runs broadly down the alignment for approximately 2km (mostly within the WHS) to a new
road junction (just outside the WHS), again on the solstitial alignment. This raises serious concerns that the integrity of the SW sightline from Stonehenge could
be destroyed, eliminating forever the possibility of visitors to Stonehenge once again seeing the winter solstice sun setting behind the distant natural horizon
along the axis of the monument.
The winter solstice sightline to the SW from Stonehenge is the single most important sightline in the WHS, reflecting as it does, the design of the monument.
However, its integrity is compromised by the existing A303 road, crossing the sightline just c.500m from Stonehenge, and by three plantations of tall trees each of
which blocks the view to the distant horizon, formed by part of a hill c.1km WNW of Druid’s Lodge (4.4 km from Stonehenge).
The proposal clearly has benefits, in particular by removing the A303 from the landscape immediately to the south of Stonehenge, which at present seriously
compromises the integrity of the SW sightline. This would not only help restore the monument to its landscape setting but would also eliminate the stream of
vehicle lights passing within 250m of the monument which that are so intrusive at night.
Nonetheless, the current proposals appear to be directly contrary to Policy 3c in the 2015 Management Plan (see above) and the strategies for implementing it
[ECS15]. We should be aiming to preserve this key sightline for eternity. Trees are temporary; on the other hand, the landscaping accompanying major roadworks
could compromise the sightline irreversibly.
Lighting (either fixed lighting or vehicle lights) needs to be avoided along the full extent of the sightline. Even at a distance of a few kilometres, lighting would
affect the view directly along the sightline at sunset or at night, running counter to all the progress being made in restoring the site to its landscape and sky.
Ideally, and perhaps essentially, the landscape topography within the SW sightline (solstitial sector) should be left completely intact. Only this would guarantee
absolutely that the integrity of the sightline is preserved for the future. This would imply that the western tunnel entrance would have to be to the west of this
solstitial sector, and that no part of the approach road should be cut through this sector.
A crucial question, then, is whether it might be acceptable for any road structures to be placed within the sightline, but too low to be visible from Stonehenge in
the absence of trees. The following concerns, at least, would need to be addressed:
a) All parts of the road and its associated earthworks and structures within the solstice sector would need to be invisible below the natural topography (in the
absence of trees), i.e. screened behind natural ridges (even when these have been cleared of trees) and below the distant horizon. Under no circumstances
should existing or additional trees be used for screening.
b) All vehicles must be screened from view at all times. Not only would vehicle lights be intrusive at night: the eye would be drawn to any movement during the
daytime. This implies that at all points the road surface must be at least 5m below the visible natural topography (when cleared of trees) and horizon. In particular,
there must be no direct view of headlights/rear lights from vehicles, especially those travelling directly or almost directly towards or away from the monument.
c) For a two-level road junction, given that road vehicles may be up to 5m in height, (a) and (b) imply that the ground surface would need to be at least 11m below
the viewshed from Stonehenge at every point.
d) Even if no lighting is installed at the tunnel entrance and junction, having these structures within/on the sightline opens up the possibility that lighting will be
required (perhaps as a legal requirement, e.g. because of altered health and safety regulations) at some point in the future. This would be damaging.
e) There may still be diffuse or reflected light from vehicles at night.
In sum, no part of the road, built constructions (bridges, viaducts) or earthworks, signage, vehicles, street lights, vehicle lights, or diffuse or reflected light from
vehicles should be visible along the sightline. Trees cannot be taken into account: any screening by trees is temporary but changes to the visible topography are
permanent and irreversible. It would be doubly bad to rely on trees to screen the road, related constructions, or lights. The onus would need to be upon the
planners and road engineers to demonstrate that the proposed structures would NOT compromise the sightline. This would not only involve topographic
modelling; it would also require specialist input from archaeoastronomers.
Even if the concerns above are addressed, we recognise that such a road may have adverse impacts on other attributes of OUV and this would need to be
addressed. Additionally, it is possible that the road and related works might still be visible from other points along the sightline, such as from the “Sun Barrow”
immediately to the NE of Normanton Gorse. This is relevant to Attribute 3 as well as Attribute 4. The composite visibility plan (Map 10) in the 2009 Management
Plan [MP09, p. 184] may be helpful in regard to this issue, and full and detailed “bare earth” topographic modelling will be needed to ensure that all attributes of
OUV including Attribute 4 are fully taken into account.
[ECS15] Chadburn, A. and Ruggles, C. (2015). Stonehenge World Heritage Property, United Kingdom: Extended Case Study.
[MP09] Young, C., Chadburn, A. and Bedu, I. (2009). Stonehenge WHS Management Plan 2009. English Heritage, on behalf of the Stonehenge WHS
Committee. www.stonehengeandaveburywhs.org/assets/Full-MP-2009-low-res-pdf.pdf
[MP15] Simmonds, S. and Thomas, B. (2015). Stonehenge, Avebury and Associated Sites World Heritage Site Management Plan 2015 (ed. Nichols, E. and
Tyson, R.). Published on behalf of the Stonehenge and Avebury WHS Steering Committees.
[SHV11] English Heritage. 2011. Seeing History in the View. A method for assessing Heritage Significance within Views

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