HS2 Ltd. / EKFB / ASC | England 2019 - ongoing

Located on the northern edge of the Chilterns Area of Outstanding Natural Beauty, the Small Dean Viaduct will run through a copse near the southern tip of Wendover village, spanning a tightly aligned trunk road, minor road and railway cutting at a pronounced skew. The skew angle strictly limits suitable locations for piers however the proposal nevertheless achieves a balanced and symmetrical arrangement of spans that, from a distance, appear to nestle in a natural depression in the landscape. By contrast to its sibling structure at nearby Wendover Dean the constraints of the site combined with the pronounced diagonal alignment and low deck level will result in an especially dynamic appearance when viewed from the carriageway – bringing a powerful sense of ‘infrastructural drama’ as the deck passes overhead through the tree canopy.

The skew alignment at Small Dean makes the pier design particularly important – the transverse ‘face’ of the piers will be visually prominent, being presented at either side of the carriageway to anyone travelling along the A413 London Road. The level of detail and a consistent, legible, architectural language is therefore of special importance: the form, detail and finish will come under particular scrutiny in this location. In the case of both the Wendover Viaducts the formal expression of the piers takes on anthropomorphic quality - arms and hands holding the bridge deck in a ‘Y’ form – a legible expression of structural forces coming down through the widely spaced bearings and into the slender stem of the pier column.  

The pier form also allows for the placement of supports at a closer proximity to the A413 – the hammerhead is located at an elevated height relative to the clearance envelope of the carriageway and this contributes to the even spacing of the supports.  The formal characteristics of taut edges and soft radial transitions in the pier design cascade to the design of the parapets, noise barriers and viaduct abutments.

“The (HS2 Independent Design) panel applauds the quality of the project team’s collaboration with Buckinghamshire Council...
...the design of Small Dean Viaduct (is) successful: it is an elegant structure, enhanced by well crafted details.”