DRIVERS are being advised to avoid making journeys on roads between Bristol and Bath this weekend as the M4 is closed to remove a condemned bridge.
National Highways’ contractors will be taking down the bridge carrying the A432 Badminton Road over the motorway at Wick Wick, near Downend.
It means the M4 has to close in both directions between junction 18 with the A420 at Tormarton and 19 with the M32 at Hambrook.
The M4 will close from 7pm on Friday March 21 until 6am on Monday March 24.
Motorway traffic will be diverted along the M32, A4174, A420 and A46 through Hambrook, Downend, Emersons Green, Warmley and Wick (pictured above in blue).
After drivers leave the M4 or M32, only the A4174 Avon Ring Road is dual carriageway – and parts of the westbound carriageway are currently subject to roadworks, with narrower lanes and a 40mph speed limit.
National Highways, which is in charge of the motorway, is also advising people not to come to the area to watch the demolition. It is setting up an exclusion zone around the site and has erected hoardings around it.
People wanting to travel during the weekend are also being warned that rail services between Bristol and London are being severely disrupted on Sunday March 23 because of engineering works.
National Highways says the motorway usually carries 3,000 to 4,000 cars per hour between Bristol and Bath at peak weekend times.
‘Expect disruption’
Route Manager Sean Walsh said: “We carefully plan our schemes to limit any inconvenience, but sometimes it’s not possible to carry out the work that’s needed without a closure.
“Our message for anyone who plans to travel on the M4 around Bristol this weekend is to avoid the area if you can – if that’s not possible, allow yourself plenty of extra time to complete your journey via our signed diversion routes and expect delays.”
The diversion route is the same one used in October last year, while work was done to build trenches for new gas and water mains, electricity and fibre optic cables that had previously been carried by the bridge.
Back then many drivers tried to avoid the signed route by using other local roads – but found themselves stuck in jams.
There were long queues on Westerleigh Road between Emersons Green and Dodington, with traffic approaching the A46 backed up for two miles beyond Codrington at some points.
People also reported queues on Siston Hill, Goose Green and through Pucklechurch during the previous closure.
Railway sleepers and shipping containers
National Highways’ engineering manager for structures Terry Robinson (pictured above, in front of the bridge) says that once the M4 is closed, contractors from Taylor Woodrow will move a pile of railway sleepers currently stacked next to the hard shoulder onto the motorway to create a 1,600 square metre crash mat beneath the bridge to protect the road surface.
They will then put 400 tonnes of aggregate on top of the sleepers and place a row of shipping containers on top of that, to absorb the impact and break up the concrete bridge structure when it comes down.
Workers will remove the sides of the bridge and allow the main deck to collapse onto the containers.
Several massive crushing machines will then pulverise the bridge, before the rubble is taken away to a compound next to the motorway to be separated into concrete and steel for recycling.
Mr Robinson said the middle span of the bridge will be removed first before everything else, including the piers, or upright supports, and the concrete foundations either side of the motorway.
He said: “There will be two-and-a-half thousand tons of material to remove.”
Around 45 people will work in 12-hour shifts during the demolition process.
Demolition will start in the early hours of Saturday and continue throughout the day, followed by a clean-up operation through Sunday and into the early hours of Monday.
The intention is to completely remove all of the bridge structure, leaving the embankment clear for the new bridge, which will be installed between this autumn and next spring.
Workers were removing asbestos pipes from the bridge on Thursday and Mr Robinson said that there would be no asbestos in the main structure when it is demolished.
No public viewpoint
National Highways is setting up a 50m exclusion zone around the bridge during the demolition work and says members of the public should not try to access the site.
To the south of the bridge, the A4174 is part of the diversion route and has no parking facilities, while to the north, the agency is closing the Cuckoo Lane junction with the A432 Badminton Road to all traffic, pedestrians and cyclists from Thursday evening until Monday.
Residents of Cuckoo Lane will be able to access their homes via Down Road and Bury Hill.
The demolition team have set up a remote relay from a camera trained on the bridge that can be viewed by visitors at the western end of their compound, next to the ring road, but this will only be accessible to people coming on foot.
New 50mph limit
After the bridge is removed the M4 carriageway around it will be narrowed, and a 50mph speed limit will be introduced for the next year, until the new bridge has been completed.
There will be at least one and possibly two more closures between the autumn, when the beams for the new bridge will be installed, and next spring when the bridge is due to reopen.
Mr Robinson said the design for the new bridge had been finished and National Highways was in the final stage of choosing a UK-based firm for the contract to build it.
The final cost has not been confirmed but is expected to be around £20 million.
Mr Robinson said the new bridge’s beams would be made from ‘weathering steel’, which has a specially-formulated layer of stable rust that seals off the rest of the metal from the elements.
It does not need to be painted and is very low maintenance.
The new bridge is being designed to last 120 years – the same lifespan as the old bridge, which was was opened in 1966 but found to be unsafe for motor traffic during a routine inspection in 2023.
The old one was a ‘post-tension’ structure, with steel cables inside the concrete, and found to have “accelerated deterioration and cracking”.
The new bridge will not have the moving parts present in older structures, such as bearings, which need to be replaced every 50 years, and joints that need replacing every 15 to 20 years, as the whole structure is designed to expand and contract as temperatures change.
It will also be 4m wider than the old bridge, with the same space for road traffic but room to carry wider cycle and pedestrian paths to link up with those planned by South Gloucestershire Council on the A432.
Mr Robinson said: “When it’s finished it will be a better facility for everyone.
“It should never need painting, although it will look rusty!”
Trains disrupted
Train operator GWR says trains will also be disrupted this weekend.
Network Rail is completing planned engineering works along the mainline between Didcot and Swindon, which means GWR trains will need to use alternative routes to serve Bristol and South Wales.
It says a “significantly reduced, amended timetable” will be in place for services between London and Bristol Temple Meads, and South Wales on Sunday.
The closure of M4 also means there will be no rail replacement services between Bristol and Swindon.
GWR Operations Director Richard Rowland said: “We’re sorry for the impact this work will have on journeys between London and Bristol and South Wales. We advise customers to change plans if possible and only travel on Sunday if absolutely necessary.
“This works means that we are only able to run very few trains on this route and those that will run will be really busy.”
As well as significantly busier trains, journeys will also take much longer. Services may also be cancelled or delayed at short notice.