Early contractor involvement and canny decision-making have yielded savings of around £1.8m at Lichfield in Staffordshire.
Project: Lichfield Bridge
Client: Staffordshire County Council
Client: Stoford Developments
Contract value: £3m
Region: West Midlands
Main contractor: Galliford Try
Start on site: November 2014
Completion date: November 2015
The development of a business park in Lichfield, Staffordshire faced a raft of headache-inducing challenges. At its simplest level, it needed a beefed up service road and bridge rebuild. The catch was the cost.
“Everyone was committed to the Christmas possession deadline and missing it would have cost the council £300,000-£500,000”
Stephen Knott, Galliford Try
Since the route – Burton Old Road – bridges over the West Coast Mainline as it enters the business park, this 1911 structure must be demolished and rebuilt to meet current road standards.
Galliford Try won the £3m early contractor involvement contract to replace the bridge in August 2014. But at that stage there were many unresolved risks that could have stalled the project for up to a year, possibly even shelving it altogether if cost-effective solutions were not found.
The main risk was accessing the north side of the bridge after the original one had been demolished (see box, below).
An ECI cost solution
“This project is only possible because of ECI,” says Amey project manager (working with Staffordshire County Council) Stephen Knott. “Everyone was committed to the Christmas possession deadline and missing it would have cost the council £300,000-£500,000.”
At the time of Construction News’ visit in mid-July, Galliford Try was lifting the last components of the new bridge into position, having demolished the original structure during a 54-hour possession over Christmas and Boxing Day in 2014 (see box, below).
The contractor installed the 12 main bridge beams during two separate overnight possessions at the end of June and beginning of July. Getting to this stage has required significant preparation and careful planning due to limited working methods permitted near the railway and access constraints.
The road bridge was originally Network Rail-owned, but is being replaced by a project jointly funded by Staffordshire County Council and Stoford Developments, developer of the business park, and will be a council asset on completion.
“Development at the site had been stalled for more than 15 years because of the complex and costly infrastructure requirements,” says Mr Knott. The total project is worth about £6m.
Planning permission for the business park was granted on the condition that the Burton Old Road Bridge, would be rebuilt to accommodate heavy goods vehicles, a combined pedestrian footpath and cycleway, and safe containment over the railway.
It will also carry services across for the new 10 ha development. The business park, which will be known as Liberty Park, will contain offices and warehouses, creating more than 1,000 jobs. Its triangular site is bound by the A38 and WCML and London Midland railways (see diagram).
Demolishing the bridge without damaging the overhead power lines for the railway was one of the first construction risks assessed by the team.
With little time before the Christmas 2014 possession, Galliford Try secured the services of supply chain partner Colas Rail to lower the power lines onto the ground, protect them with panels during demolition and reinstate them immediately after the work was complete.
‘The bridge is made up of 12 simply supported beams with abutments at either end resting on spread footings onto rock’
John Dixon, Amey
The alternative would have been to demolish as much as possible without damaging the cables during the 2014 possession, and demolish the remainder in a separate Christmas 2015 possession, at a cost of £110,000.
Construction of the new bridge began in earnest in January 2015. “The bridge is made up of 12 simply supported beams with abutments at either end resting on spread footings onto rock,” explains Amey senior structural engineer John Dixon. “Due to time constraints, we went for the simplest solution to meet Eurocode requirements”.
The beams weigh between 33 and 40 tonnes, and parapet members weigh 9 tonnes each. The bridge is 5 m wider than the original bridge and spans 25.8 m between bearings. Widths for the carriageway, pedestrian/cycleway and verge are 7.3 m, 2 m and 1.7 m respectively. The concrete pad foundation supporting the bridge approach structures is between 2 m and 3 m thick.
Bridge construction activities, which take place near or over the railway, are carried out over the course of about 30 night-time railway possessions, which are up to seven hours long. These activities include erecting hoardings near the railway, erecting scaffolding and formwork for the concrete abutments and installing bearings, beams and parapets, as well as finally pouring the deck concrete.
The bearings were installed in June and have been designed for longitudinal, transverse and thermal movement and impact. Deck concreting is due to take place in August, with bridge completion due in November.
Forming the side beams that support the bridge parapets are ‘U’ section beams, while inner beams are all inverted ‘T’ sections. The precast concrete beams are 1,360 mm deep and positioned at 1 m centres along the width of the bridge, with a 30 mm gap between the bottom flanges. These bottom flanges create a lower-deck level where operatives can safely work (see diagram).
Plates cast into the beams feature eyes that provide safe lifting points.
Quicker with concrete
A standard steel parapet will be used to contain vehicles on the bridge. Usually, these members are connected to the concrete deck via a cast-insitu concrete plinth. But due to the nature of working within tight possession windows, these plinths have been redesigned by Amey as 9 m-long precast concrete members so that they can be fixed more quickly.
The plinth also provides a means of edge protection when the deck is being concreted. The deck will be 200 mm thick, with a 400 mm edge thickening.
Across the project, value engineering the design and construction method has delivered significant savings. By redesigning the bridge to skew across the railway track, adjusting its width and redesigning the abutments, the new structure no longer bears onto a 450 mm-diameter high-pressure Victorian cast-iron water main. Diverting the pipe would have cost £100,000 and would have significantly delayed the project.
The approaches to the bridge have also been value engineered to save £315,000. Here, instead of building retaining walls on the bridge approaches, one has been replaced with an embankment, which also reduced pressure on the water main, and the other three have been redesigned as reinforced earth walls.
Although the project would probably not have gone ahead if the haul road solution had not been found, these other savings, including £275,000 from changing the alignment of the highway, amount to £800,000 on the £3m contract.
Including the haul road solution, £1.8m of savings have been made on the Midlands scheme, largely down to getting the contractor involved early.
Staffordshire County Council had to appoint a contractor for the project as quickly as possible, to be in a position to carry out bridge demolition during the Christmas/Boxing Day railway possession, which had been pre-booked.
It used the Midlands Highways Alliance as a first port of call to select a suitable partner and used the ‘direct call-off’ mechanism to appoint Galliford Try because of the contractor’s experience on similar projects, its health and safety record and best price based on a model scheme.
“The Midlands Highway Alliance provided the perfect opportunity for us to collaborate with stakeholders and make this challenging project the success that it is,” says Galliford Try framework manager Gary Morris.
Early contractor involvement between August and November 2014 allowed key decisions to be made swiftly and jointly to ensure the project would stay on programme, and significant construction and cost risks could be reduced.
Appointing Galliford Try using a NEC3 option C – target price with activity schedule – contract got the ball rolling to solve the main challenge on the project: how to access the north side of the bridge (which is enclosed by the A38 dual carriageway and two rail lines) once the bridge has been demolished.
Building the northern abutment before Christmas 2014 was one option considered by the team, but time and cost constraints meant that this was unfeasible, especially as the bridge had yet to be designed.
“Another solution was to build a slip road and access ramp off the elevated A38,” says Galliford Try framework manager Gary Morris, “but because of the proximity to other junctions [and potential traffic disruption], this was rejected by Highways England. It would also have been a very costly solution.”
Nearby level crossings could not be upgraded to support the weight of construction traffic either, so another solution had to be found.
Past experience of working on the rail projects alerted the contractor to look into historic haul routes nearby. A suitable 2.5 km route from a main road near Huddlesford across arable land was identified and extended to the site.
Galliford Try designed the route to support a 1,000-tonne crane in transit and gained permission from three landowners to allow the haul road to be built in just 10 weeks.
This involved clearing vegetation, excavating to base level, laying a geotextile and depositing 8,000 tonnes of clean hardcore quarry material along the route. Work started on the haul road on 24 November 2014 and was completed in the week before Christmas.
“The solution cost just £250,000 compared with the £1m-plus cost of building the north-side works,” says Amey project manager Stephen Knott.
Crucially, building the haul road meant that access to the north of the site could be maintained during the entire project, significantly reducing the risk of work overrunning. In fact, the quarry material will be reused in the business park development, diminishing the haul road’s actual cost further.
Christmas Day possession
The original two-span Burton Old Road Bridge provided access to a house and a carpark for Lichfield Trent Valley Station. It also had a 7.5 tonne vehicle weight restriction.
The car park had to be permanently relocated and residents of a nearby house were treated to a stay in a hotel for the inconvenience caused during bridge demolition during Christmas and Boxing Day 2014.
The 54-hour possession was meticulously planned: “We produced an hour-by-hour programme to demolish the bridge during the possession,” says Galliford Try project manager Sunil Karra.
The first operation was to survey the track, lower the power lines on the ground and protect them with panels. Two mobile cranes began by extracting the bridge parapets, which was followed by demolition of the deck and central pier.
Excavators on the protected track removed demolition arisings and deposited them on the business park site for later reuse. So risk averse was the operation that lorries were not relied upon to transport the arisings further away in case they got stuck in snow, causing a delay in the super-tight programme.
“Network Rail reviewed progress during the possession every three hours. If things were running late, the whole operation could have been called off to make sure the railway opened in time,” says Mr Karra.
After the bridge demolition, site workers reinstated the power cables and surveyed the track prior to handover.
In the final tally, the original bridge was safely demolished and the railway line was handed back with a few hours to spare.
Total savings: £1,791,382
- Lowering overhead-line equipment to allow the entire bridge to be demolished during the Christmas 2014 possession and, therefore, not requiring an additional possession in 2015 to remove the remaining bridge. Amount saved: £110,000
- Value engineering the highway alignment. Amount saved: £275,032
- Creating a haul road to allow site access to the north side for the duration of the project and not requiring the north abutment to be constructed ahead of demolition. Amount saved: £991,350
- Redesigning bridge with a skew to avoid the water main and not requiring the water main to be diverted prior to new bridge construction. Amount saved: £100,000
- Redesigning the bridge approach’s four concrete retaining walls as an embankment (which also reduced pressure on the water main) and three reinforced earth walls. Amount saved: £315,000