A shock discovery has found that one of the main supporting piles in Shaldon Bridge is made of deteriorating wood – not the concrete and steel construction shown on the original plans.
New weight restrictions on heavy lorries have been imposed indefinitely and divers are waiting for the next neap tide to check underwater and see if any other piers also have wooden piles.
A statement from Devon County Council’s highways engineers says: “Shaldon Bridge’s original construction drawings show that the bridge’s piers are each made up of four concrete piles, which are encased in steel and concrete.
“However, the inspection unexpectedly revealed that one of the piles inside a pier was made from timber instead of concrete, which has started to deteriorate.
“A site investigation next week will determine if there are more timber piles and also confirm the condition of the one timber pile so far discovered.
“Previous inspections have confirmed concrete piles on other piers.
“The focus of the investigation will be on the five piers in the deep-water channel. Because the piers are permanently submerged inspections are extremely difficult and can only be carried out by commercial diving contractors.
“The inspection will take place next week, during the next neap tide, from Monday 29 October through to Friday 2 November. This is to ensure that the flow of water is not too great for the divers to safely work. Even then there is only a two-hour maximum working window.
“The weight restriction coincides with the scheduled daytime closure of the bridge today (Wednesday, 24 October) to partially raise the bridge. The bridge must be raised once every one to two years in accordance with an Act of Parliament which requires that the bridge remains operational.”
Double decker buses may be banned and all vehicles over three tonnes are banned indefinitely – except for emergency vehicles and the winter gritters.
The construction was the longest wooden bridge in England when it opened in June 1827, but after 11 years the centre timber arches of the bridge collapsed, eaten through by shipworms.
It was rebuilt in wood and reopened in 1840, but it partially collapsed again in 1893.
The bridge was completely rebuilt between 1927 and 1931.
At that stage it was reported that steel was used for the piers and main girders and concrete for most of the deck, except for the opening span which used timber.
Now a temporary three-tonne weight restriction is effective immediately after the defects were discovered by engineers during a recent inspection.
Devon County Council said: “Traffic across the bridge will be maintained while the inspection work takes place and updates will be provided by Devon County Council engineers when they have completed their investigations.
“The council’s Transport Co-ordination Service is currently talking to the bus company about using a single decker bus instead of a double decker and this too will have an exemption.”
Local Councillor, Alistair Dewhirst, said: “I have been assured that the overall condition of the structure is good, and the weight restriction is purely a precaution. Engineers inspect the bridge regularly and is safe to use.
It is essential however that drivers of vehicles that exceed the 3 tonne limit use the signed diversion route. We do not know how long the weight restriction will be in place at this stage.”