Highways England have commendably included a mass of technical documents on their consultation page about the Stonehenge Tunnel (Do visit it, read it and leave feedback). They include the technical reports and particularly in TAR appendix G and H they score their proposals against the various aims and policies of the stakeholders.
I have read and searched as thoroughly as I have been able to in the limited time I have had these documents and I have failed to find where they have scored their proposals against two key policies. There is a thin gloss over a generalised Policy 3 from the WHS management plan but it fails to discuss the meat of Policy 3c (see below) and I can find no reference at all to UNESCO's Statement of Outstanding Universal Value which discusses the astronomy of the WHS (also below).
This oversight is so egregious that it invalidates the whole technical assessment, it needs to be redone.
Placing a tunnel portal directly on the most important astronomical alignment of Stonehenge fails these policies so badly that it draws the whole plan into doubt.
It is a pity that the Highway engineers didn't take dear Oscar's advice and rise up from the gutters and look at the stars.
From Full Description (IAU Extended Case Study format): Stonehenge World Heritage Property, United Kingdom
A retrospective Statement of Outstanding Universal Value (SOUV) was prepared for the Property by the State Party in 2011 and has been approved by UNESCO. The relevant parts of that SOUV in relation to astronomy are quoted here:
Statement of Significance
The Stonehenge, Avebury and Associated Sites WHP is internationally important for its complexes of outstanding prehistoric monuments…
They provide an insight into the mortuary and ceremonial practices of the period, and are evidence of prehistoric technology, architecture and astronomy…
The complexes of monuments at Stonehenge and Avebury provide an exceptional insight into the funerary and ceremonial practices in Britain in the Neolithic and Bronze Age. Together with their settings and associated sites, they form landscapes without parallel.
The design, position and inter-relationship of the monuments and sites are evidence of a wealthy and highly organised prehistoric society able to impose its concepts on the environment. An outstanding example is the alignment of the Stonehenge Avenue (probably a processional route) and Stonehenge stone circle on the axis of the midsummer sunrise and midwinter sunset, indicating their ceremonial and astronomical character…
UNESCO’s Astronomy and World Heritage Initiative adds: "Assuming that these were once largely clear in the Neolithic and Bronze Ages, it is important to try and ensure that the sightlines are as clear as possible today. All plans should ensure that no further development takes place along them."
Stonehenge and Avebury World Heritage Site Management Plan 2015 lays out various policies including:
Policy 3c – 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