The Stonehenge related artefacts and sites have been proven to extend for miles beyond the existing main site.
The tunnel they are building is a ‘cut and cover’ trench that will have its entry points well within the extended site that is known to contain valuable archaeological information.
There were two main things that they could have done to minimise the irreparable damage – 1) build a longer tunnel so that it extended beyond the site & 2) bore a tunnel, not dig a trench – both solutions were more expensive than this plan, so we’ve gone for the cheap & cheerful option.
The air pollution won’t be reduced – just moved along the road. Noise pollution is a different matter – but for what?