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A trio of southern bridges

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Willingdon Tree, Oyster Pond and Cat’s Back – three delightful names, but what are they? The answer is they are all footbridges, recently installed on the network at Eastbourne, Newhaven and Wandsworth respectively. They all also presented their own challenges – a level crossing so dangerous it had to be closed before its replacement bridge was ordered, long pedestrian diversions and protected trees in the way of craneage.

All three were installed by   B&M McHugh, based in south London and holders of the minor works contract for Kent and Sussex. However, these three projects were awarded as individual design and build contracts from GRIP stage 3 to 8.

Willingdon Tree

This pedestrian-only crossing was a lightly used means of access from a housing estate onto the Willingdon Levels, a lowland marsh area used for agriculture and recreation. The crossing was located between Polegate and Hampden Park stations in Eastbourne, on a slight curve, with 80mph traffic and up to 145 trains crossing each day.

In the normal course of events, its replacement by a footbridge would have been relatively low priority in Network Rail’s plans to eradicate level crossings. The key issue that raised its risk rating to C (Very High) were the number of near-misses reported – 19 incidents in five years. These included a near miss with a young child aged between 8 and 11, and two girls observed sitting in the four-foot, very close to touching the conductor rail.

Such was the concern with the risks to young users that Network Rail took the unusual step of seeking permission from East Sussex County Council to temporarily close the crossing to users for seven months until a footbridge could be provided.

Network Rail’s route managing director for the South East, John Halsall, described Willingdon Tree crossing as “one of the most frightening level crossings on my route”.

To allay local concerns at this temporary lack of access across the line to Willingdon Levels, Network Rail held a local public meeting on 7 November 2016. Network Rail’s route managing director for the South East, John Halsall, told the meeting: “We have seen several incidents where people, including children, could have been killed and we also know that young people use this crossing as a means to trespass on the railway.

“I know this will come as a shock to some, but I cannot leave this crossing open. I’m keen to work with the community to close it, so we can keep them – and their children – safe.”

Following the meeting, the crossing was closed off by palisade fencing on 13 November 2016. At the meeting, local anglers, who used the crossing daily to access a fishing lake, were vociferous in their concerns at the lack of a suitable alternative access route. As a result, Network Rail agreed to provide a pontoon footway through an adjacent bridge over a drainage channel. However, the floating walkway provided to meet anglers’ concerns was in reality barely used.

The proposed footbridge was to be a standard steel structure with a span of 14 metres. The layout of the Network Rail land boundary, and the land purchased, resulted in a straight stair on the Down side and a 180° cranked flight on the Up side. The design for this was undertaken by Ipswich based MLM Group.

Work to build the bridge began in January 2017, with the construction of the foundations, which were 12-metre-deep CFA piles installed by a Klemm 709 rig working during normal hours behind hoardings. The trestle and stair steelwork erection by B&M McHugh personnel took place in an eight-hour rules of the route possession on 22 April, and the bridge span during another possession on the 23rd.

The bridge was completed and opened to the public in May, as had been promised at the public meetings. It has received a positive reception from the local community and, importantly, removed a high risk crossing from the railway.

As the bridge was located adjacent to private gardens, and also as a result of the site’s history of stone throwing at trains, it was agreed that the mesh screens would be provided throughout.

Oyster Pond

The footpath from Beach Road to Seaford Beach in Newhaven passes over the single line railway between Newhaven Harbour and Bishopstone stations on an ‘Exmouth’ type footbridge. This design of precast concrete bridge, a product of Exmouth Concrete Works, was widely used by the Southern Railway and Southern Region, from the early 1920s to late 1970s, but many have since been replaced as corroding reinforcement and spalling concrete weakened them.

Oyster Pond footbridge had been deteriorating for some years and, to maintain its integrity, had a temporary timber prop on the down line formation (see below) and the trestles had been encased in blockwork.

In 2015 Network Rail approved the replacement of Oyster Pond footbridge with a standard steel structure.

Like the bridge at Willingdon Tree, the land available meant the layout was asymmetric, with a single flight on the Up side and a 180° cranked flight on the Down side. The new bridge is of twin track span to permit future doubling here and is located four metres west of the existing structure. This optimises the use of available land for the stair flights and also permitted the new foundations to be constructed prior to the demolition of the concrete structure.

An early task was therefore to gain planning approval for the repositioning of the new bridge from Lewes District Council, which was achieved on 20 October 2015. The formal closure of the footpath by East Sussex County Council began on 1 February 2016 and a very long diversion alongside Mill Creek provided to maintain access to Seaford Bay beach.

Working closely with MLM Group, the design was developed to incorporate the extensive experience of fabricating steel footbridges for Network Rail by fabricator Convira Group.

Network Rail land to the west of the site provided a compound for B & M McHugh whilst the working access to the site was through a Southern Water sewage treatment works. Work to build the bridge began in January 2016, with the construction of the foundations, which here were CFA piles driven 19 metres deep through alluvial and fluvial deposits, again installed by a Klemm 709 rig working during normal hours behind hoardings.

A good working relationship with the Southern Water operations team enabled a 500-tonne crane to be positioned in the works. The old bridge was demolished in a single 57-hour possession on 12/13 May and the new structure erected in two eight-hour rules of the route possessions on 6 and 7 May.

The completed bridge reopened to public use on 4 April 2016.

Cat’s Back footbridge

Cat’s Back footbridge is a pedestrian and cycle bridge, located between Clapham Junction and Wandsworth Common stations, which provides a crossing point over the four-track cutting that dissects Wandsworth common.

The bridge deck, 3.8 metres wide, was of steel trussed girders with concrete-encased cross girders and a heavily spalled concrete deck. In 2015, Network Rail agreed to replace the superstructure.

B&M McHugh was awarded the contract to replace the superstructure with a standard steel footbridge of similar width and to upgrade the side span parapets and surfacing.

As the only crossing point of the line within the common, it was a well-used bridge by walkers, runners and cyclists as well as by pupils at Northcote Lodge School, whose pupils used it to reach their playing fields. A long diversionary route was provided alongside the railway boundary to Bellevue Road at the southern end of the common, returning on the opposite side.

The key problem to be overcome in planning the project was the craneage for the demolition and construction works. Wandsworth Borough council was concerned that several of the common’s mature trees would have to be removed or heavily trimmed to enable a 250-tonne crane to access the works, and so they requested that a larger crane be used. As a result, the project was planned around the use of a 1000-tonne Demag AC1000 road crane, located 50 metres back from the bridge, with lifts planned over the tree canopy.

The works started on 3 January 2017, with the team first carrying out work to the side spans during normal working hours. Abutment brickwork repairs took place during night-time rules of the route possessions.

On 13 January, a temporary trackway for that weekend’s crane and lorry access was laid across the common. This ran from Bolingbroke Grove to the site using Dura-Base HDPE panels laid directly on the grass.

The existing span was lifted out for offsite demolition and recycling at the start of a 52-hour possession on 14/15 January. Temporary timber bracing had previously been installed between the parapets to ensure the span could be lifted safely.

The existing bearing shelf was broken out on each side using hydraulic breakers mounted on 13-tonne excavators. The crane placed new precast cill beams on each abutment before adding the new steel superstructure, designed by MLM Group and fabricated by Nu-Steel. The following day, the temporary access trackway was removed, returning the common’s grass to normal use.

Final finishing works followed, with the bridge being completed by 24 February. It was formally opened by students from Northcote Lodge School on Tuesday 22 March.

Bruce Karsten, vice-principal of Northcote Lodge School, said, “Network Rail has done a great job in keeping us up to date with the works and we are grateful that they have completed everything so speedily.  The boys are looking forward to being able to use the bridge again on their way to and from school as well as having access to the sports pitches across the railway line.”

So, three great names for three much-needed new bridges. Cat’s Back is probably the highest profile, while Willingdon Tree was arguably the most necessary in terms of public safety. But all were installed in a timely manner and are welcomed by their local communities.

Who said that footbridges were simple structures?

Written by Bob Wright

Bob Wright
Bob Wrighthttp://therailengineer.com
SPECIALIST AREAS - STRUCTURES, RAILWAY INFRASTRUCTURE. Now retired, Bob mainly worked in general contracting with May Gurney, and latterly Kier, and was involved with various Network Rail structures frameworks. For the last 40 years Bob has been a voluntary civil engineer on the North Norfolk Railway, latterly as Director. He also acts as a consultant to a number of other preserved railways.


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