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Archaeology, diversions and a collapse: Hochtief/Taylor Woodrow's link road has it all

From tackling an unexpected cutting collapse to improving saturated ground, the project has thrown up a range of challenges.

Project: Bexhill to Hastings link road
Client: East Sussex County Council
Contract value: £75m
Region: South-east
Main contractor: Hochtief
Main contractor: Taylor Woodrow
Lead designer: Jacobs
Project manager: Mott MacDonald
Start date: July 2013
Completion date: May 2015

Despite being less than 6 km long, the Bexhill to Hastings link road runs through a town, a disused railway cutting, a flood plain and up a hill.

This varied environment poses a number of different challenges for the Hochtief/Taylor Woodrow joint venture building the road for East Sussex County Council.

The single carriageway is designed to relieve congestion, improve connectivity, encourage local growth and increase access to the countryside.

Hochtief / Taylor Woodrow was appointed as design and build contractor in 2009 and, after a lengthy delay caused by the government’s initial austerity measures, started on site last summer.

A temporary access road had to be created, almost the length of the final highway, to allow materials and machinery to reach the critical section in the rural flood valley between the two towns.

Extensive ground improvement

“The main area we have to do a lot of work in is the rural centre of the route,” says Mott MacDonald supervisor Mark Foster.

“The ground was very soft for a depth of up to 12 m. We had to do ground improvement works, which required 170,000 tonnes of stone to be brought in.”

“Using the controlled modulus columns with three rigs meant we could install more than 200 piles in a day. Sometimes with CFA piling you only do 15 in a day”

Mark Foster, Mott MacDonald

Four streams cross the route of the link road within this flood valley, requiring bridges to be built on the soft ground.

The project team opted to pile with controlled modulus columns to prepare the ground for structures over the Watermill and Powdermill streams at the heart of the Combe Valley, where the ground was at its softest. Taylor Woodrow’s sister firm Menard undertook the piling.

“Using the controlled modulus columns with three rigs meant we could install more than 200 piles in a day,” Mr Foster says. “Sometimes with CFA piling you only do 15 in a day.”

Site workers installed vertical band drains around the Combe Haven and Decoy streams on the western and eastern edges of the valley to accelerate the movement of water through the earth.

In total, 13,000 piles and 16,000 vertical band drains were used on this central section of the project. They allowed load transfer platforms to be created with 68,000 tonnes of stone to spread the weight of the road and structures over the reinforced ground within the heavily saturated valley.

A race to beat the weather

Most of the ground improvement works took place last autumn and into the winter with the target of beating any harsh weather. This proved to be an extremely wise move as the valley flooded when the severe storms came in January this year.

“It was fantastic to have the piling finished,” says Taylor Woodrow project director Richard Wall-Morris. “It was quite an achievement and meant we had access to start the next stage in the spring.”

Following on from the ground improvement works was the start of earthworks.

On the two outer streams, soil is being taken from other parts of the site and placed onto 500 mm-thick piling mats, with the pressure and the specialist drains squeezing out moisture until the ground reaches the required strength.

“Rather than adding 400 mm of soil each week, we check the levels and top up daily. This gives a great benefit as we have been able to add 1 m per week, an improvement of more than 100 per cent”

Richard Wall-Morris, Taylor Woodrow

Chosen for its cost effectiveness, this process is none-the-less time consuming, and every effort has been taken to minimise the impact on the programme.

Mr Wall-Morris says careful co-ordination and monitoring has allowed quicker soil compaction.

“Rather than adding 400 mm of soil each week, we check the levels and top up daily,” he says. “This gives a great benefit as we have been able to add 1 m per week, an improvement of more than 100 per cent.”

Reinforced concrete abutments are being formed for the bridges, and work has begun on the embankments leading up to them. The project team is working to find the most cost-effective way of preparing the soil for the sub base before laying the road surface itself.

But the challenges are far from confined to this difficult rural section.

Cutting collapse

Moving from there towards Bexhill, there is 600 m of road to be located in an old railway cutting. In December 2013, with the project hurtling towards a start on site, 200 m of this cutting collapsed.

“We have to stabilise it and ensure it remains safe,” Mr Foster says. “We are currently working with East Sussex County Council to come up with an engineering solution that will do this within its budget.”

This stabilising work is due to start in September. When the road is complete it will run through the cutting, underneath a rebuilt Ninfield Road bridge and into Bexhill.

Ninfield Road bridge is another major obstacle for the project team to overcome, being ill-suited for allowing traffic to run underneath it.

It needs to be demolished and rebuilt, but this poses several problems as it currently carries traffic, pedestrians and a variety of services from the A269 into the town and down to the coastal road.

The team arrived at the solution of using the first section of the link road – running for 1 km from Ninfield Road to Belle Hill junction – as a temporary diversion for traffic, while erecting a temporary bridge for walkers and to carry services.

So this first section of the link road needed to be open before the critical works rebuilding the bridge could begin. On top of this, completing the first section will also provide access to begin stabilising the cutting.

“This 1 km was a very complicated section in itself,” Mr Wall-Morris says. Among other things, the contractor had to build an underpass and re-work a major junction.

The underpass was required at Chapel Path to allow school children to cross the link road safely. Earthworks raised the ground level for the link road to pass overhead.

At Belle Hill Junction, where the Bexhill-to-Hastings road meets the A269 and the A259, a new road layout is needed. New traffic islands have been created, and ducting for the signals installed, with resurfacing taking place this month.

Problematic bridge

A bridge carrying Woodsgate Road in Bexhill was also found to be unsuitable for the link road to pass underneath, and had to be partially rebuilt.

This sub-project was hit by a number of obstacles including worse ground than expected, a flood at the steel beam supplier’s factory, and a shortage of the bricks required to match up with the retained abutment.

The overall programme was unaffected, however, and the 1 km section is due for opening in August, unlocking the next series of works to link it to the Combe Valley leg.

“Archaeologists prefer to preserve what is under the ground in situ if possible. It is better if we can avoid sensitive material altogether”

Bob Pape, East Sussex County Council

At the other end of that tricky rural section, the link road rises up a hill and across the London-to-Hastings rail line to meet the B2092, or Queensway, where it ends.

The main challenge here is building the bridge over the railway. A reinforced concrete culvert is required, along with the realignment of nearby Crowhurst Road.

A concrete pour for the railway bridge’s eastern abutment took 15 hours, with work still to come on the west abutment and central pier.

Some 20,000 cu m of earth from this hilly section will find a new home as landscaping across the site.

A 900-tonne crane will lift and fit the 45 m long beams for the railway bridge during overnight possessions of the railway from late July.

“It will be a fantastic milestone for the link road project when these beams are in place,” Mr Wall-Morris says. “It will free up our concrete subcontractor Sian to start on the deck and get us on the way to completing the structure.”

Once all the structures are in place across the route, the base materials can be laid, followed by the road surface. Although plenty of challenges remain, the complex project remains on schedule for completion next May.

Prehistoric finds

A series of excavations carried out before the project began revealed occupation of the area at around the end of the last ice age – more than 10,000 years ago.

Concentrations of finely worked flint artefacts have been recorded along with pits containing charred hazel nuts, fire places and stake holes that were used for a structure of some kind.

These sites, which give great insight into how early hunter-gatherers were living in East Sussex, also pose a dilemma to the link road project team.

It is required to dig ponds in Combe Valley to mitigate the effects on the flood plains of the embankment and road. But it doesn’t want to displace historically important material and add cost to the scheme.

“The design of the road through the flood plains on Combe Valley is highly regulated by the Environment Agency,” says East Sussex County Council project manager Bob Pape.

“Archaeologists prefer to preserve what is under the ground in situ if possible. It is better if we can avoid sensitive material altogether,” he adds.

Trial pits are being excavated to give a clearer picture of where the places to avoid may be. The team will then work towards a solution suiting all parties.

 

Ecology preservation

Looking after the ecology of the land used for the link road has been important to the project team.

Badgers are being relocated from setts impacted by the scheme, with talks continuing with Natural England over proposals for the railway cutting area. Two animal crossing tunnels and badger fencing are to be installed.

Regularly maintained reptile fencing has kept reptiles and newts out of certain areas of the construction site.

Adams Farm barn, which had evidence of being used as a bat roost, has been dismantled and rebuilt with retained material and features that attract bats.

As well as this, over 300 dormouse nest boxes were erected in woodland throughout the site.

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