The dualling of the A465 that cuts through the south Wales valleys is aiming to kick-start economic regeneration in a deprived area. But one section of the road required Carillion to build a number of new structures in difficult conditions.
Project: A465 Heads of the Valleys dualling, Section 3: Brynmawr – Tredegar
Client: Welsh Government
Main contractor: Carillion
Environmental co-ordinator: TACP
Piling subcontractor (Cemetery Road section): Bam Ritchies
Piling subcontractor (Carno Underpass): Cementation Skanska
Piling subcontractor (Tredegar): P J Edwards & Co (UK)
Road surfacing: Lafarge Tarmac Trading
Plans to upgrade the road between the ‘Heads of the Valleys’ in south Wales have been on the agenda since the mid-1990s.
This crucial trunk road connects Abergavenny in the east with Neath in the west, skirting the Brecon Beacons National Park.
The area around the road is a deprived one, and it’s hoped that dualling the old three-lane carriageway can act as a catalyst for economic regeneration. “It will kick-start regeneration, allowing people to get to and from jobs, and hopefully encourage businesses to open up along the road,” says Carillion project manager on the scheme Mike Cummine.
Carillion acted as main contractor on section three of the A465 dualling, a 7.8 km stretch between Tredegar and Brynmawr, which was completed on time and under budget in September last year.
Overall, the entire road will be dualled in six sections: sections one, three, and four have been completed; section two is under way and due to open in 2018; while sections five and six will be delivered in one contract that’s due for completion by 2020.
Section three required a remarkable amount of work along its 7.8 km-long route.
The team had to build four junctions, eight bridges, six large retaining walls and three underpasses, along with a rest area at the road’s highest point and 5.1 km of new cycleway to extend the National Cycle Network.
Beginning work in 2010 under Early Contractor Involvement, Carillion worked with Arup and TACP to draw up an initial design.
“We ended up having just three objections at the public inquiry stage”
Mike Cummine, Carillion
The team undertook extensive public consultation at this ECI stage (see box) to try to work out how their activities would affect the community, and what road design would best meet their needs.
“We ended up having just three objections at the public inquiry stage,” Mr Cummine says. Carillion then began work on the detailed design and construction in January 2013.
The European Regional Development Fund, recognising the scheme’s potential for regenerating a deprived area, provided around half of the funding for the project, nearly £80m.
Of the 14 major new structures that were built, the Carno Valley Crossing is perhaps the most impressive and technically interesting. Here, the new road crosses a 30 m-deep valley, south of Carno Reservoir.
“Originally we were going to build a 170 m-long viaduct over the valley, but as we had a great deal of excavated material from the rest of the project we began to look at alternative solutions,” Mr Cummine says.
Instead, the team decided to use this excavated material as fill for a large embankment.
“It’s also an advantage for the client, as it’s far easier to maintain an earth embankment than a viaduct”
Mike Cummine, Carillion
As there were restrictions on the footprint of the embankment, retaining walls had to be built to hold back the fill material. The team built three tiers of reinforced earth walls, forming a terraced structure above a culvert that would allow spillway water to pass underneath and maintain road access for Welsh Water, the owner of the reservoir.
“This had the big advantage of giving us a 10 per cent carbon reduction in the construction phase,” Mr Cummine explains, thanks to the fact that 300,000 cu m of earth was retained in the embankment, and concrete was saved from being used in the viaduct. Overall, the 28 m-high embankment produced a saving of more than 8,000 tonnes of carbon.
“It’s also an advantage for the client, as it’s far easier to maintain an earth embankment than a viaduct, where the deck would require re-waterproofing and other maintenance through its life,” Mr Cummine says.
The culvert at the bottom is a precast concrete arch, 18 m wide, 9 m high and 150 m long. Each segment weighs 28 tonnes and was lifted into place using an 80-tonne crawler crane.
Watch a timelapse of the work being done:
Between a rock and a hard place
The road’s location provided another set of challenges, too, in that its path is situated over a number of abandoned mines.
“We’re on the edge of Wales’ old iron and coal fields, so we spent a lot of time mapping those out and understanding what was there,” Mr Cummine says.
The team filled the old mines with cement grout underneath all of the structures to mitigate settlement, but used geogrid reinforcement underneath the roads themselves.
“It was a much more cost-effective solution than grouting everything up,” he says.
“It’s effectively a plastic grid that sits underneath the road pavement. If a mine working opens up underneath it, instead of a hole opening up in the road you would just get a dent, giving the maintainer an opportunity to go out and repair it before it becomes an issue for the road user.”
Catalyst for regeneration
The project team liaised extensively with the local community throughout the project, beginning at the ECI stage, resulting in just three objections when it came to the public inquiry into the Compulsory Purchase Orders.
In addition, with the project acting as a catalyst for regeneration, it was vital that local suppliers and contractors were used wherever possible.
The team created an on-site ‘Job Shop’ in partnership with Blaenau Gwent Council’s employment team, with 99 per cent of workers employed through this scheme coming from Wales.
It was also the first project in Wales to receive National Skills Academy for Construction status from CITB, and the first highways project to do so anywhere in the country. The external funding provided through this allowed the team to provide 86 new entrant trainee jobs, including 27 apprenticeship starts at Level 2 and 3.
In total, 84 per cent of the project cost was spent directly with Welsh companies, too, resulting in estimated economic benefits of £180m.
Additionally, the geology of the area posed challenges, with extremely hard rock in some areas bordering peat bogs in others, creating variable ground conditions across the project.
One structure, a new 12 m-high retaining wall built alongside Dukestown Cemetery to separate it from the road, required piling subcontractor Bam Ritchies to construct a continuous line of concrete piles drilled into the rock below the finished road level.
“I think this was the hardest of our three piling solutions, although all three were carried out very well,” Mr Cummine says.
“Bam used a down-the-hole hammer and they discovered that some of the rock was some of the hardest they’d ever encountered. They actually broke their DTH hammer because it was so hard and had to get another one.”
The team overcame numerous other challenges, not least the wild Welsh weather – Tredegar in particular was the wettest place in Wales in January 2014, with 370 mm of rainfall.
As well as the usual problems of working in such wet conditions, the team had to carefully manage water runoff, using Siltbusters to ensure that silty water wasn’t flowing downstream.
“We’ve all been more interested in the project than our individual employers, and we’ve delivered on our promises”
Mike Cummine, Carillion
The new junction and underpass at Tredegar was also complex, requiring a phased, top-down construction process to divert a number of services and cables, with careful planning to get to the new road layout.
Carillion’s work on this section of the Heads of the Valleys is only part of the bigger picture. But the combination of a large number of new structures, heavy civil engineering in wet and hilly areas, and careful management of risks from abandoned mine tunnels and complex geotechnical condition presented huge challenges.
Getting on board and collaborating was vital to ensuring the project’s success, with the designers and environmental co-ordinator TACP all integrated into one project team with Carillion.
“We’ve had a very good team. To integrate like this you need all the parties to come to the table with the right mindset, which we certainly did here,” Mr Cummine says.
“We’ve all been more interested in the project than our individual employers, and we’ve delivered on our promises.”