Plans to construct a tunnel link for the A303 route past the famous Stonehenge monument have hit further problems. This follows a report from the National Audit Office
(NAO) questioning the value of the proposed 3.2km tunnel. The NAO’s report suggests that the return on investment will be slim for the project, and that it will offer no economic benefit at all should the costs increase further.
The project is expected to cost in the region of €1.7 billion to €2.73 billion, largely as the ground conditions along the proposed route are poor. The rock is heavily fragmented and fractured, while the water table is high. The former means that the tunnel will require considerable support, while the latter will necessitate the installation of extensive drainage systems that will also have to meet tough environmental requirements. The proposed tunnel route has also attracted criticism from archaeological groups, saying that will be too close to the monument and will likely risk damage to further historical finds in the area.
There have been suggestions to move the tunnel further south or to make it longer still, but these would boost the construction costs higher still. In addition, funding has yet to be finalised for the project. The current plans call for the tunnel to be complete at the end of 2026, although commencement of construction has now been held back from March 2020 to December 2021 at the earliest.
There have been plans to build a tunnel to replace the existing A303 link in the past, which have been cancelled for various reasons, most notably the high cost. However despite the controversy over the tunnel, it is also worth noting that the existing A303 link running past Stonehenge is unable to cope with current demand. Featuring just one lane in either direction along this stretch, delays are frequent at peak periods, particularly in the holiday season when the route carries heavy holiday traffic.