Contractor opens door to Scotland’s latest golfing development with new M8 junction involving rapid demolition despite appalling weather conditions.
Project: New M8 Junction 4a – Heartlands
Client: Ecosse Regeneration
Contract value: £9.1m
Main contractor: Balfour Beatty
Demolition subcontractor: Beattie Demolition
Lead designer: Fairhurst & Partners
Start date: September 2012
Alex Muirhead is a man focused squarely on a long-held vision.
The Ecosse Regeneration development director doesn’t see forgotten mountains of treated spoil, overgrown stores of top-soil and crude haul-roads running through the huge chunk of Scotland’s central belt that makes up the Heartlands Development site.
He sees golf fairways, housing developments and booming business parks.
It is difficult to look beyond the last vestiges of the Polkemmet Colliery on the outskirts of Whitburn and visualise the glittering future for the Heartlands project.
But that vision is moving one step closer now that Balfour Beatty is constructing a new junction onto one of Scotland’s busiest sections of motorway, the M8, that whisks travellers to and from Glasgow and Edinburgh.
This privately financed project will be critical to the redevelopment of the 610 ha site and Mr Muirhead is excited.
“The motorway junction will be the cornerstone of the development,” he says. “It is a vitally important part of the project.”
Under a £9.1m deal, Balfour Beatty is working on the project to provide the grade-separated junction that will serve the development.
Construction manager Alan Thompson is charged with the delivery of the new junction. “We have been involved in the project for some time and had been looking forward to getting on site, but there were a few setbacks,” he says.
A supermarket chain had been set to help finance the scheme but it pulled out of the project as the economic downturn started to bite. Finding the cash to invest on a new motorway junction has taken some time.
“Given that we had been looking at the project for so long, mobilisation wasn’t a problem”
Alan Thompson, Balfour Beatty
Eventually though, with private funding secured from the Royal Bank of Scotland, Balfour Beatty took the scheme under an NEC Option A deal following an open tender process which saw the contract awarded in August 2012.
Just a month later the Balfour Beatty project team was on site and focusing on its delivery. “It was quite a quick turnaround, but given that we had been looking at the project for so long, mobilisation wasn’t a problem,” Mr Thompson says.
However, building a new motorway junction with an overbridge, two roundabouts and four slip roads is no simple task.
Factor in the demolition of an existing reinforced concrete bridge over the motorway (see box), the realignment of a 750 mm-diameter main that pipes water from Loch Lomond all the way to Edinburgh, and the redirection of one of central Scotland’s major rivers, and the level of complexity soon starts to mount.
The embankment to each roundabout and to the access road that feeds the junction is founded directly onto the boulder clay sub-soil.
“Material that was already on site is competent, weather-friendly and economical. It has worked perfectly for both us and the client”
Alan Thompson, Balfour Beatty
Thanks to this layer there is no need for any difficult piling work beneath the embankment. Instead, the Class 1A graded, granulated fill is laid in 150 mm layers and compacted using a standard Bomag 213 roller.
Fill material has been site won from across the Heartlands development and has proven to be more than competent.
“We haven’t used any specialist equipment during the earthworks,” Mr Thompson explains. “There are no settlement issues underneath the embankment.
“Material that was already on site is competent, weather-friendly and economical. It has worked perfectly for both us and the client.”
The same material is being used to found the fairways on the two Professional Golfers Association-designed 18-hole golf courses that are due to be built on the development (see box).
Supersize slip roads
Both the eastbound and westbound on-slips are 800 m long, almost twice the length of the 450 m off-slip roads. This is largely down to the congestion and traffic flows that are expected around the new junction, giving drivers merging onto the motorway more time to edge their way into the traffic flow.
Similar to the embankments, there are no piled foundations beneath the two bridge abutments either side of the motorway.
These too are cast directly onto the underlying boulder clay that surrounds the site, although a few local soft spots of peaty material were treated prior to casting.
“We cast directly onto the exposed boulder clay on both the north and the south side, although there were some earthworks needed beneath the northern abutment,” Mr Thompson explains.
The bridge itself spans 50 m using three pairs of steel beams some 1.5 m deep in section, with each pair weighing 110 tonnes, landed on top of the abutments.
The beam pairs were brought up in sections from steel fabricator Rowecord’s south Wales base and assembled during a two-week window in a laydown area provided alongside the bridge’s southern abutment.
“There are three braced pairs of beams that span between the abutments with welded and bolted connections. They were lifted into position using a 550-tonne luffing jib crane,” Mr Thompson says.
Bridge lift delay
The initial plan had been to lift the three pairs of bonded beams into position during a single overnight possession of the motorway.
Unfortunately thanks to the adverse weather conditions which hit the country in the first quarter of 2013, that proved impossible and the installation was completed over two weekends.
The bridge features a slender 290 mm-thick reinforced concrete deck, covered by a minimum 125 mm overall surfacing thickness.
“It took us a little under two years to completely remove any evidence of the burning bing”
Alex Muirhead, Ecosse Regeneration
The beams are cambered and ‘hog’ slightly over their length; to counteract that hogging effect, the concrete for the deck is poured in three stages totalling 264 cu m.
The first pour is within the middle bay in the centre of the span and counteracts the hog while the two outside bays at each abutment are poured simultaneously.
Precast concrete coping sections weighing as much as 11.5 tonnes are then fixed across each side of the bridge; there are 16 in total.
Once completed and fully opened to traffic, the new junction 4a on Scotland’s M8 motorway will provide the gateway to Heartlands and breathe fresh life into one of the country’s largest regeneration schemes.
Twelve-hour bridge demolition
As plans for the project progressed it became obvious that the existing twin-span service bridge that provides access over the motorway would have to go.
With its location almost at the tie-in point of the westbound on-slip, the team had little choice but to demolish the bridge and provide improved access at the new junction.
But the demolition of a reinforced concrete motorway bridge across one of the busiest sections of motorway on the network is no easy task.
Specialist contractor, Kilsyth-based Beattie Demolition, was brought in to carry out the work during a single night’s possession.
The closure started at around 10pm. Once the team got the all clear to work, crash mats were placed on the carriageway to protect its surface before starting the intricate work of bringing down the bridge.
The demolition plant and equipment was brought onto site at around 11pm, with two machines working on breaking out the concrete on the bridge decks on the northern and southern side of the central pier.
A further eight machines were working from the carriageway itself, breaking, separating and clearing material.
“They broke out as much of the deck as possible to expose and remove the beans,” Mr Thompson explains. “Once the beams were exposed the piers were taken out.
“The whole bridge was down by around 4:30am. Then it was just a question of separating out the steel and concrete as far as possible.”
By 7am on the Sunday morning, barely nine hours after the Beattie team had taken over the motorway, all the demolition arisings – steel beams, reinforcement and concrete – had been sorted and cleared from the carriageway.
All that was needed was to replace the crash barrier to the central reservation. The team cleared the site and had the carriageway open by 9:30am, less than 12 hours after it began.
A kiss of life to the Heartlands
The new motorway junction is vital to the success of the new Heartlands development.
The £650m mixed-use development will see residential, retail, business and sporting-led investment brought into the area.
Sitting on the 610 ha site of the former Polkemmet Colliery, the land has been brought back into use where many had given it up for good. Ecosse Regeneration managing director Terry Walker had the foresight to see through the sites problems and look at its potential.
Among the biggest of those problems was the removal of several huge mounds or ‘bings’ of colliery waste – coal, sandstone and mudstone.
One of these had been smouldering for years and was known as the ‘burning bing’; a massive mound of 2.5m cu m of waste that was on fire and had burst back into flames during several attempts to mitigate it.
“We managed to do what others had failed,” Mr Muirhead says. “It took us a little under two years to completely remove any evidence of the burning bing.”
The first residents of the initial swathe of new homes being built on the former colliery site have now moved in and other housebuilders are in negotiations with the developer.
Initial work on the two golf courses has also started and the new business park is attracting interest.