RIBA bridge competition ends in nothing

The project to build a new footbridge in Stratford-upon-Avon has come to an unhappy end, and one not entirely untypical of bridge competitions. It has been cancelled due to "spiralling costs".

In 2006, RIBA ran a bridge design competition for a new footbridge over the River Avon in Stratford, garnering over 60 entries. Five entries were shortlisted in November 2006, and the winner announced as Schlaich Bergermann & Partners with Ian Ritchie Architects, with a super-slender steel arch design (pictured). This was an interesting reaction against a trend towards structurally gymnastic cable-supported bridges which had dominated high-profile footbridge design.

The promoting authorities' support for the bridge always seemed to be in doubt. It was promoted by Warwickshire County Council, but there was considerably opposition in the local press to what was seen as an unnecessary scheme, and the council's lukewarm attitude was reflected in consultation after consultation, with associated feasibility reports and pedestrian studies. Most of these were prepared after the competition had already begun, suggesting that a genuine need for the bridge was never conclusively demonstrated.

The original scheme budget was £2m, which is ample for a bridge that is 50m long, and is 3.71m wide. That works out at over £10,000 per square metre of deck, which is plenty for almost any footbridge, however unusual (for dimensions, see the original design submission at Warwickshire's website).

Now, however, Warwickshire have spent £312,000 on getting the bridge to planning submission stage, and have in the process re-estimated the bridge's budget cost at £3.3m, an increase of over 50% and equating to over £17,500 per square metre. Not unsurprisingly, the project has been cancelled, with the council quoted as saying "neither the County or District Councils are in a position to fund the shortfall so we have reluctantly decided to remove the bridge from the World Class Stratford programme." Given that Warwickshire were only going to stump up £0.2m of the original budget (the rest coming from external development funding), it's easy to understand their decision.

So what really went wrong?

The council's original budget certainly wasn't at fault, for what should have been a fairly straightforward and simple river footbridge. There are several competitions where the budgets are unrealistically low, certainly in comparison to the effort expected from entrants. The need for repeated studies and consultations, as well as the low budget contribution from the main stakeholder suggest a lack of commitment which won't have helped. Surely a proper feasibility study prior to holding an expensive competition would have helped establish a firmer case for the bridge (or led to its cancellation prior to spending so much money)?

The council has chosen to blame construction price inflation, particularly steel prices, but any sound project should assess risks such as this at the outset and take them into account throughout. Steel price inflation wasn't an unknown when the winner was chosen in late 2006.

Was there something particularly risky about this design that the council could have spotted and dealt with? The "glasgowbridge" competition was one high profile case where the winning design came in well above budget (like Stratford, subsequently cancelled), and where it was apparent that the design was structurally challenging, to say the least. Was that the case here?

The Stratford design was an arch that was both very slender (50m span and only 350mm thick at midspan, a span-depth ratio of 142), and with a very shallow rise. The former will have made it susceptible to dynamic excitation, and the latter will have created an unusually large horizontal thrust on the abutments, but it's hard not to think that these could both be addressed within the original budget.

The council also cites "additional flood mitigation measures" as increasing the cost, and it may be the case that there are issues beyond the bridge itself affecting the scheme.

I'd ask whether a RIBA competition was the right approach to such a minor structure. The Stratford bridge isn't the only RIBA competition to go nowhere due to uncertain funding and commitment from the promoter - another happened at River Wear in Sunderland.

One lesson perhaps is that ambitions should be scaled to match the resources really available (including the willingness to deal with risks); another could be that the conventional non-competition design process (feasibility study, preliminary design, detailed design etc) may uncover problems at an earlier and more cost-effective stage.