Engineers to lift M32 bridge by half a centimetre for £200m repair programme
Works are due to start in 2026 on refurbishing the Eastville Viaduct of the M32
Engineers will raise a motorway bridge in Bristol by half a centimetre as part of an extensive programme of repairs costing £200 million. Works are due to start in 2026 on refurbishing the Eastville Viaduct of the M32, replacing corroding bearings and fixing cracking concrete.
National Highways hope to keep two lanes open in each direction while the works take place, although drivers could face 30mph speed limits and narrower lanes. Some slip roads at Junction 2 will also be closed temporarily, as they need refurbishing.
Noise barriers will also be installed along a long section of the motorway, benefiting many residents living in houses nearby, some just 10 metres away. But these residents will also have to put up with incredibly noisy work such as blasting off the edges of the bridge.
Sean Walsh, route manager for National Highways, said: “Like any infrastructure, as you would with a car, they have a life expectancy and you need to go in and replace things. This structure is around 50 years old now and there are elements of it, some of which are moving, that are coming to that point where they need replacement.
“The working assumption is that we’ll keep the road open. Individual slip roads will close for extended periods and we’ve already started talking with our local authority partners to model and see what the likely impact is on local roads. There will be disruption but hopefully it won’t be what people initially imagine.”
A recent freedom of information request revealed the flyover, built half a century ago, needed extensive concrete repairs. In an interview with the Local Democracy Reporting Service, Mr Walsh said he wanted to take the opportunity to “renew rather than repair” the 1.16-kilometre bridge.
On top of pillars holding up the bridge are 128 bearings, which enable the structure to move as the concrete expands and contracts with changing temperatures. These are the original bearings installed when the viaduct was built in two phases, in 1970 and 1975. Engineers will replace all of these gradually, but need to raise the sections of the viaduct one at a time.
Terry Robinson, engineering manager at National Highways, said: “On hot days the bridge is bigger than it is on a cold day. So it has to move, and the bearings enable it to slide. But these bearings need to be replaced, as they wear out. For us to get them out, we’ve got to actually jack the bridge up.
“We might have to shut the road while we jack it up, but once it’s jacked up we lock the jacks off and we can run traffic over it. It’ll be an overnight project to jack the bridge up. We’ll continually leapfrog our way over the bridge.”
For the 63,000 vehicles who drive over the bridge on an average day, the speed limit might be reduced from 40mph down to 30mph. Once the works are completed, it’s unclear if the speed limit would be raised above 40mph due to the benefits to air quality of driving slower.
It’s also unclear exactly how long the repairs will take, but they are due to start in either 2026 or 2027. National Highways has been working on the project for four years, which is now going into the detailed design phase.
The central reservation will be removed, so that traffic can be temporarily moved around the bridge as works take place on the top side of the structure. A new central barrier will be installed, but left in a way that could lead to new bus lanes being created in future. The works also include new lighting, barriers, surfacing, signage and gantries.
A large area underneath the bridge has long been left empty, except for a popular but improvised skate park. Part of the repairs will see this space improved for the local community, which could include more artwork, a refurbished skate park, or even extending Eastville Park.
“We would like to leave a positive legacy for the land under the bridge,” Mr Walsh said. “It’s not our land but we have begun conversations with others where the community could reclaim this land. There’s some quite tangible possibilities down the line.”
One problem with the concrete, which can be clearly seen from below, is the many areas of spalling. This is where concrete has broken away from the underside of the bridge, exposing the reinforcing steel. A major factor contributing to this is the blocked drainage system, which is due to be completely replaced and made easier to maintain in the longer term.
“All of the spalling elements are down the middle,” Mr Robinson said. “That’s because there’s a trough that goes right the way down the middle of the bridge underneath the barrier, and that carries the main drainage pipe. It’s unmaintainable for us, we absolutely can’t get to it. So there’s a lot of water seeping through the trough.
“A lot of bridges have got spalling concrete. It’s not ideal. When concrete was first used it was seen as a wonder material, it was going to be indestructible. It’s not, we’re learning that now. But with good care and maintenance, that can be repaired quite easily.”
A particularly noisy part of the work will be removing the edges of the bridges, and recasting new edge beams, as new noise barriers and vehicle barriers will be too heavy for the existing edges. But this work will be done during the day, to avoid keeping nearby residents awake.
“We’ve going to have to take the edges off the bridges,” Mr Robinson said. “The parapets are coming down and we’ll put new parapets back. There will be noise barriers as well. But all of that means the existing edge beams are not strong enough, so we’ll have to literally cut the edges off the bridge and recast new edges.
“Refurbishment of a structure like this, especially in an urban area, is a real challenge. These are complex structures very close to people’s houses, so working conditions are going to be difficult with limited spaces. This is business as usual for us, albeit on a larger scale and in an urban area. The structure is safe and sound.”
“Whatever we do we have to be sympathetic to the surroundings,” Mr Walsh added. “You wouldn’t want to do very loud intrusive work during the middle of the night, but then that extends the period. It’s a balancing act between the needs of the community and getting the work done.”
Some people have suggested demolishing the entire flyover. However this raises several problems including where traffic would be diverted, as well as the fact much of the motorway runs over the River Frome, so a replacement bridge would be needed if the road was kept. And demolishing the structure would be “very difficult”, with the potential to go badly wrong.
“Demolition is an idea that’s ebbed and flowed over the years,” Mr Walsh said. “You would need to get the road down to the level of the Eastville roundabout, so that would require significant cutting. Crucially you also have to acknowledge the community and the effect that demolition would have on them and their properties.”
“This has got cables running through it that are under quite a lot of tension squeezing the concrete together,” Mr Robinson added. “To demolish a post-tension structure is very, very difficult. It’s not just a case of sending a breaker up there and breaking it down, it’s a whole different ball game. If you don’t get it right, it’s like a rocket going off at each end.”