Walker Construction recently completed a £1.2million design and build contract to install a new foot and cycle bridge over one of Kent’s busiest railway lines, the collaborative efforts of the entire team successfully resolving a long-term road-safety issue. Project manager, Jim Arnott (right), and site manager, Paul Maxton (left), describe the project.
Network Rail’s Thanet Line runs across north Kent carrying commuters and holiday makers to-and-from the Kent seaside towns of Herne Bay, Margate and Ramsgate. A mile east of Herne Bay station the track runs through a cutting and under Blacksole Bridge, a five-arch brick bridge carrying Margate Road over the line.
As Herne Bay has grown the volume of vehicle and pedestrian traffic using Blacksole Bridge has increased substantially but, without a pedestrian footway, it’s gained a notorious reputation. Signage warns ‘No footway for 120 yards’ and, with a blind bend at the south end, crossing the bridge is hazardous. Local residents, fearing a serious accident, have vociferously campaigned for a solution for years, their vigour reaching a crescendo when it was announced that Blacksole Farm, to the south of the bridge, was to be developed.
But the plan promised the solution they wanted. In 2003, Canterbury City Council granted planning permission to the Kitewood Group for the creation of the Altira Business Park, a high-quality, 30-acre industrial/commercial development. One of the conditions the council imposed was that a pedestrian bridge had to be provided but, to the intense dismay of the campaigners, not until 17,000m2 of the site had been developed.
Kitewood entered into an Option Agreement with Urban&Civic to provide a Sainsbury’s superstore and petrol station on part of the site and in June 2013, Kitewood, in conjunction with Urban&Civic, submitted a planning application for the bridge, fast-tracking its provision by waiving the 17,000m2 trigger. As Richard Hepworth, Director of Project Management at Urban&Civic, said, “We take a long-term view of everything we do and tend to invest in infrastructure first – the bridge provides connectivity to the store and we wanted that in place as soon as possible.” It was a hugely popular decision, one that led tireless campaigner, former local councillor Peter Vickery-Jones, to exclaim “I have had my arguments with Kitewood in the past but all that is forgotten and forgiven – I just want that bloody bridge!”
Walker Construction won the contract to provide the new bridge along with its associated access points, lighting, a fully-lit footpath into Altira Business Park, access routes for inspection and maintenance, security fencing and landscaping. Overall design of the scheme was passed to Walker Construction’s design division, WSS Construction Consultants, the design, construction and installation of the bridge being awarded to Hythe-based bridge and gantry fabrication specialist Nusteel Structures.
Nusteel proposed a single-span Warren Truss Bridge, its versatile design concept allowing different cladding and parapets to be used to create a unique, eye-catching structure. Armed with this, ‘a small army’ of WSS engineers and designers started work on the multitude of design facets involved. The 52m-long bridge would be positioned parallel to the existing road bridge and approximately four metres to the east, allowing immediate access to the existing pavement on the north side and needing a straightforward, 150m-long footpath to connect with The Boulevard in Altira Business Park on the south side.
Preliminary work on site started in July 2015 and soon revealed an unexpected hazard when “the ground began releasing a pungent-smelling smoke which obviously caused concern.” (Walker Construction Incident Report). The fire brigade were called, a search revealing nothing more than several broken bottles, an innocuous find next to a bridge over a railway line. Although the incident prompted an environmental investigation, the discovery of three intact bottles both solved the mystery and raised the stakes: they were No.76 Special Incendiary Grenades, ‘Molotov Cocktails’ used by the Home Guard during the Second World War and probably left by the bridge ready for use in the event of the threatened invasion in 1940. The police were called, the area cordoned off and the Army’s Explosive Ordnance Disposal team contacted. A further ten grenades were found and transferred to a skip, where a controlled explosion destroyed them and the phosphorus left to burn itself out. Work on the site would have to proceed with caution!
As work progressed, Walker Construction, WSS, Nusteel, the developers and the stakeholders worked together in a series of design coordination meetings to ensure that the project’s technical aspects were addressed and that Kent County Council and Network Rail’s criteria were met, WSS co-ordinating and managing an extensive approval processes on behalf of both.
As the bridge spanned a busy mainline railway, Network Rail’s requirements were particularly rigorous, their review covering every aspect of the project from start to finish. Working next to a live railway line meant the site had to comply with ALO (Any Line Open) working conditions which meant creating a working environment in which there was no danger of machinery on the site fouling the line in the event of either human error or an accident. Inevitably, this can only be achieved by introducing a physical barrier between the working area and the track, the type of machinery used and the site’s topography determining the strength of the barrier. In this instance, a piling rig, albeit a small one, was to be used at the top of each embankment, the risk being mitigated by using 7m-long, sheet steel piles to create a barrier, these being driven into position during Network Rail line blocks. Pragmatically, WSS designed the piles to also form part of the temporary works system that created the piling mat and, after trimming them down, to form the retaining wall around the lower part of the bridge abutments.
Work started on 7 September 2015, the site being prepared ready for the construction of the two reinforced-concrete bridge bases that would be located at either end of the bridge. Piletec Geotechnical bored six, 450mm diameter, 9m-deep pile shafts for each base using sectional flight auger (SFA) piling to allow a small rig, a Klemm 702, to be used. SFA piling is quiet, vibration free and overcomes the need for casings or bentonite to support the bore. Shafts are bored to the required depth using a hollow-stem auger which is then slowly retracted, drawing the spoil with it, the resulting void being filled by a high-slump concrete pumped down the auger’s hollow stem. Once the auger has been removed and the bore filled, a steel reinforcing cage is inserted into the still wet concrete.
As the bridge was to be constructed and finished in Nusteel’s workshops and then craned into position, a high degree of accuracy was needed to ensure the fixing points on the bridge lined up perfectly with the holding down bolts cast into the bearing shelves on the bridge abutments. With a design tolerance of just 15mm, site manager and project engineer Paul Maxton’s setting out had to be absolutely spot on.
Construction of the bridge started in Nusteel’s Lympne workshops in January 2016, some four months after work had started on site. Built by a team of three craftsmen and two apprentices, the bridge was constructed in two parts: one 42 metres long, the other 10 metres long. The bridge was painted and ready for delivery by the middle of March, its size and weight necessitating a 95-mile-trip up the M20, round the M25 and back down the M2 and A299 to the site which is just 25 miles from Nusteel’s workshop. Having arrived at the site, the two sections of the bridge were spliced together and the electrical containment fitted: the bridge was ‘good to go’!
Lifting the bridge into position was a challenge compounded by the only location for the crane being the south end of the bridge: lifting a 64-tonne bridge with a lifting radius of 46 metres across a railway line and lowering it into position with pinpoint accuracy called for something special, and very big. Sarens provided a massive 1,000-tonne, Liebherr LTM 11000 DS crane of which there are just two in the country: once on site the crane would take 24 hours to rig using the services of a second, 200-tonne crane.
After weeks of close liaison and detailed planning between Walker Construction, Network Rail, Kent County Council, Highways England, the Environment Agency, Kent Police, Nusteel, Sarens and the local residents, installation was planned for Sunday, 20 March. Network Rail scheduled a 20-hour period of Disruptive Possession on the line for a variety of maintenance purposes, during which the team were allocated a 12-hour Work Site Window to carry out the lift and complete the installation.
The actual lift involved a team of twenty from Walker Construction, Nusteel and Sarens and took place on a dry, spring day. Articles in local newspapers along with the arrival of the bridge and a massive crane ensured a sizeable audience, so-much-so that Kent Police asked that one lane of the adjacent road bridge be cordoned off and a temporary traffic management system put in place to protect the crowd.
The Work Site Window opened at 7:30am and the lift started at 3pm, taking just 20 minutes from start to finish. The bridge was gently lowered into position accompanied by applause from the crowd and audible sighs of relief from Paul Maxton and the WSS design team: alignment was perfect.
Everyone was delighted with the outcome of the project, Richard Hepworth (Urban&Civic) complimenting Walker Construction “…as one of the best contractors I’ve worked with during the last five years.” and Phil Johnson, WSS Construction Consultants’ divisional manager, describing it as a perfect example of a design and build scheme. “It’s a testament to how the developers, stakeholders, construction and design teams have worked together in perfect harmony. You frequently hear reports of dysfunctionality in D&B teams undermining the success of the project – this shows how successful they can be.”
Poignantly, the new bridge is named in memory of 20-year-old RAF Pilot Officer Albert Hugo Friday who lost his life on Friday, 30 August 1942, when his Spitfire suffered catastrophic engine failure. Although the young fighter pilot bailed out he died from his injures close to Blacksole Bridge, a memorial marking the tragic event. Local artist Kate Samuels was commissioned by Urban & Civic to design and provide the enamelled name plaques that show a flight of Spitfires over Herne Bay’s skyline.
The bridge was finished on 18 April 2016, and formally opened on Tuesday, 26 April 2016, by the then Lord Mayor of Canterbury, Cllr Sally Waters, the opening ceremony being attended by members of Pilot Officer Friday’s relatives.
Urban&Civic’s development director, Nigel Wakefield, told reporters at the opening “When we first started looking to get planning permission, we came down and met the local people. They told me the one issue they had was safely walking over the bridge. We promised them then that if we got planning for a food store, we would provide a new foot bridge.”
The local residents are delighted with their new bridge which, after so many years of taking their lives in their hands, now provides a safe method of crossing the railway. Having campaigned for the bridge since 2007, Cllr Peter Vickery-Jones voiced their thanks: “I think the developers have been really honourable with this. There was no requirement for them to install the bridge other than a moral obligation to the people of Herne Bay. I am so convinced it will save lives.”