Stonehenge A303 improvement: outline assessment of the impacts on the Outstanding Universal Value of the World Heritage property of potential route options presented by Highways England for January 2017 Nicola Snashall BA MA PhD MCIfA National Trust Christopher Young BA MA DPhil FSA Christopher Young Heritage Consultancy January 2017 ©Historic England and the National Trust Stonehenge A303 improvements: outline assessment of the impacts on the Outstanding Universal Value of the World Heritage property of potential route options presented by Highways England for January 2017 Executive Summary Introduction In 2014, English Heritage (now Historic England) and the National Trust commissioned an assessment (Snashall, Young 2014) on the potential impact of new road options, including a tunnel, for the A303 within the Stonehenge component of the Stonehenge, Avebury and Associated Sites World Heritage property. Since at that time, there were no detailed proposals, that report considered four possible alternatives and concluded that, of these, an off-line route with a tunnel of 2.9kms length would be the most deliverable solution. The government remains committed to improving the A303 and to funding sufficient for a tunnel of at least 2.9kms length within the World Heritage property. Highways England are consulting in early 2017 on route options developed since 2014 for this road scheme through the World Heritage property and bypassing Winterbourne Stoke village to the west. This report is an outline assessment of these initial options on the Outstanding Universal Value (OUV) of the World Heritage property. It has been commissioned to assess the impact of the latest road options in the light of updated archaeological information. Major changes in archaeological knowledge since 2014 relating to attributes of OUV of the World Heritage property are summarised in Chapter 2, together with any other relevant changes in the context of the current proposals. Chapter 3 describes the methodology used. Chapter 4 briefly describes the latest road options as far as they are developed and sets out the approach we have adopted. This is followed by the actual assessment of the non-physical impacts of the road options. Chapter 5 assesses the physical impact and a final chapter draws overall conclusions on the likely impact of the options presented and discusses possible mitigation measures. This assessment is still outline and provisional since detailed design of the scheme has not yet been developed at this stage of the Highways England process. It is part of an iterative process design and assessment, and its purpose is to inform Historic England and the National Trust in their consideration of current proposals and their discussions with Highways England. Based on a number of assumptions, Highways England has proposed a route which would cross the A345 by flyover with grade separated junction at Countess Roundabout. It would enter a tunnel east of the line of the Avenue. The western portal of the tunnel would be south of Normanton Gorse and closer to the Normanton Down Barrow Group than the offline route evaluated in 2014. From the western portal, Highways England is considering two alignments. Both would run through the Diamond copse. D061 would run on a more northerly alignment, crossing the A360 some 700m south of Long Barrow Crossroads. D062 would have a more southerly alignment crossing the A360 at a lower point at the Park. For both routes, the surface sections would be constructed at grade. The A360 would be crossed by a flyover for either the A303 or the A360. This would be 8m high. There would also be a grade separated junction, location to be determined. Changes in context since 2014 This report reviews changes in the wider context since our last preliminary assessment in 2014 (Chapter 2). It notes that the ICOMOS/ UNESCO Advisory Mission in October 2015 considered that the scheme could have beneficial impacts on the OUV of the World Heritage property, but also noted that the siting and design of the tunnel portals, approach cuttings, embankments, entry/ exit ramps, mitigation measures and the temporary construction works have the potential to adversely impact OUV (ICOMOS/ UNESCO 2016, 24). i Stonehenge A303 improvements: outline assessment of the impacts on the Outstanding Universal Value of the World Heritage property of potential route options presented by Highways England for January 2017 Since 2014, further archaeological work has been carried out by Historic England as part of their investigation of the southern part of the World Heritage property. Wessex Archaeology have also undertaken assessment and evaluation for Highways England. The most significant results relevant to the OUV of the World Heritage property and that could be impacted by the scheme have been the discovery/ confirmation of the existence of two long barrows and a hengiform monument in the area around the Diamond copse. This has led us to recognise a new key attribute group for this assessment, the Diamond group, located north and west of the Diamond. We have also recognised that the boundaries of the Normanton Down Barrow Group were drawn too tightly for our 2014 assessment. We have extended its boundaries to include Normanton Gorse itself, the Sun Barrow north of that wood, and the unnamed barrow group divided by the current A303 (see Fig. 2 for all key attribute groups). Methodology For comparative purposes, potential impacts have been assessed using the same methodology as last time, based on the 2011 ICOMOS Guidance on Heritage Impact Assessment (ICOMOS 2011) (Chapter 3). Separate assessments were carried out for visual and other impacts, looking in detail at the impact of the road proposals on the relationships between key attribute groups (Chapter 4) and for direct physical impacts on physical attributes (Chapter 5). We have also assessed the impact of the proposals on each of the seven principal attributes of OUV (see list on p.7) and on integrity and authenticity of the World Heritage property. Evidence for these evaluations is set out in a series of tables and overall conclusions are discussed in Chapter 6. This study builds on the work carried out in 2014 by the same authors (Snashall, Young 2014) in assessing options for a bored tunnel solution in the World Heritage property. As far as possible information from that report has not been duplicated here, and this new assessment should be read in conjunction with the earlier report. The earlier report contains additional information on the World Heritage property and fully considers the broader policy context and guidance affecting World Heritage properties. It also contains the initial assessment of the benchmark 4.5kms tunnel and the four options evaluated at the time. These are not repeated in this report. Conclusions The starting point for any assessment is the impact of the current A303 and new proposals need to be evaluated against this baseline. The 2014 report established that the current A303 has a severe adverse impact on the OUV of the World Heritage property. Both the options presented by Highways England (D061 (1) and D062 (1)) would have a less adverse impact than the current situation. On the basis of present knowledge, there would be no direct physical impacts from either option, though further archaeological work would be required to confirm this. The flyover and grade-separated junction with the A345 would have adverse local impacts but not on key attribute groups. At the east end, moving the tunnel portal east of the Avenue is highly beneficial and the impact of the road east of King Barrow Ridge and Coneybury Hill would be greatly reduced. In the central part of the World Heritage property the adverse impacts of the current A303 would be removed entirely except possibly for some distant views from King Barrow Ridge and Coneybury Hill of the surface stretches of road beyond Normanton Gorse. However, there are issues around the location of the western portal and the surface stretches of road from there to the western boundary of the World Heritage property as currently presented. ii Stonehenge A303 improvements: outline assessment of the impacts on the Outstanding Universal Value of the World Heritage property of potential route options presented by Highways England for January 2017 Physically D061 (all variants) splits the Diamond key attributes group. The western portal is very close to the Normanton Down Barrow Group while both surface routes have adverse visual and aural impacts on the surrounding Winterbourne Stoke, Normanton Down , Lake and Diamond Groups (nearly a quarter of the identified key attribute groups). Crossing of the A360 is achieved by a bridge 8m high, either of the A303 over the A360 or vice versa, with a grade separated junction. Both alignments (D061 (1) and D062 (1)) are unacceptable in this form. The 2015 ICOMOS/ UNESCO mission, quoted earlier in this summary, specifically drew attention to the potential for the surface parts of any scheme to have an adverse impact on OUV. Mitigation west of Normanton Down Barrow Group is essential and we have therefore considered five further options for each route (D061 (2-6) and D062 (2-6)) in addition to the Highways England options, considered as D061 (1) and D062 (1). Both the D061 (1) and D062 (1) routes could be mitigated, and impact on the four western barrow groups reduced by greater concealment of the road by placing it in cutting, crossing the A360 by means of an underpass and by placing any junction with the A360 to the west of the existing line of the A360 (D061 (2) and D062 (2)). Further mitigation would be achieved by moving the apparent western exit from the tunnel by construction of a landbridge/ canopy which reflects the existing landform (D061 (3) – (6) D062 (3) – (6)). This would have the effects of moving the apparent exit away from the Normanton Down Barrow Group, and also of shortening the amount of road visible in the western part of the World Heritage property.