Striding proudly across the River Mersey and the Manchester Ship Canal at the so-called Runcorn Gap is a stupendous railway bridge. Not as well known, perhaps, as some of the magnificent coastal railway bridges and viaducts, it is nevertheless impressive in its setting, immediately adjacent to the (some might say) equally impressive Silver Jubilee Bridge – the through-arch road bridge that carries the A533. Now, a £5 million scheme is underway to refurbish the railway bridge structure.

Constructed between 1863 and 1868, the Runcorn railway bridge, also known as the Britannia bridge or even, locally, as the Queen Ethelfleda viaduct, was constructed for the London & North Western Railway. The contractors were Brassey & Ogilvie, working to a design by William Baker. All of the ironwork was supplied by Cochrane Grove & Co.

Photo: GBickerdike.

Photo: GBickerdike.

Lattice

As constructed, the bridge had six wrought-iron double-web lattice girders that form three spans each 93 metres long. The wrought iron was replaced by steel in the early 20th century.

Each pair of trusses is 8.5 metres high and is linked by top and bottom box-girder chords. They support a metal deck that carries the twin-track overhead-electrified railway. There is a clearance height of 22.8 metres above the high-water mark. Each girder contains 711 tonnes of iron and is fastened by 48,115 rivets. An unusual construction method was employed in that, rather than lifting completed girders into position, they were built up piece by piece in situ.

The approach viaducts (exclusive to the present scheme) are major structures in their own right. To the north is a curving 49-arch viaduct, then a short embankment, followed by a 16-arch viaduct. A gradient of 1 in 114 was necessary so that sufficient shipping clearance height could be obtained under the central spans (The Admiralty had insisted on a clearance of 75 feet).

On the south bank there is a similarly constructed viaduct of 33 arches. All of the viaduct piers, the bridge abutments and the bridge central piers are of sandstone, with the viaduct arches being of brick.

The bridge lies on the 8.5-mile line that connects Weaver junction with Ditton junction, which today forms the Liverpool branch of the West Coast main line (WCML).

Photo: GBickerdike.

Photo: GBickerdike.

Buckingham Group

After 150 years of service, this Grade II* listed structure was requiring extensive maintenance. Buckingham Group Contracting was awarded the work as main contractor, in turn making use of Taziker Industrial, Sea Training International and Carmet Tug as subcontractors.

The scheme is currently in phase two of three. Phase 1, also undertaken by Buckingham Group Contracting, involved intrusive surveys to the main bridge piers – coring work as part of the development for Phases 2 and 3.

Phase 2 is a year long project due for completion in July 2018. It involves mechanical repairs and waterproofing of the east and west bottom cords along all three spans. The total area to be prepared and repainted is 560 square metres.

Attention is also being given to the cantilevered walkway that runs along the east side of the bridge. Formerly a right of way that was closed to the public in 1965, this footpath remains important as a walking route that gives access to the bridge spans.

The current work involves the removal, using bespoke lifting frames, of the cantilevered walking route’s cast iron parapets across all three main spans. There are 94 parapet bays in total, each 3.2 metres long and formed from five interlocking cast iron components – the top rail, two lattice panels, bottom rail and ‘bullnose’ with ornate cast iron posts between bays. The elements weigh between 100kg and 400kg each.

The recovered elements are taken off-site for refurbishment at a dedicated workshop near St Helens. Where elements are found to be too damaged for reuse, they are being replaced with new castings sourced from a foundry near Preston.

With the parapets removed, the walkway cantilevered beams and bottom chords have been grit blasted and repainted. Repairs to the steel cantilever brackets have included the removal and replacement of the end plates, so that the parapet post supports can be strengthened.

This has required the erection of three 93-metre-long underslung suspended scaffolds, which are encapsulated for the grit blasting and painting to protect the marine environment. It is estimated that 30 tonnes of grit will be used to complete the blasting across the three spans.

Installation of the suspended scaffolding was particularly challenging. Working 20 metres above the tidal River Mersey, with full exposure to the weather, made things difficult. The south span’s suspended scaffold had to be designed with reduced headroom to accommodate cargo ships using the Manchester Ship Canal.

The paint system being applied is an M24 paint system (two-pack epoxy) with a polyurethane top coat that has a matt finish to match existing colours.

Challenges

Because the bridge is so exposed to the elements, high winds passing over and through the underside of the structure have governed activities such as lifting and scaffolding works. Chinstraps are the norm when working on the bridge so people don’t lose their hats!

A wind-monitoring station is installed on the structure, linked to the site office in order to provide wind-speed alarms. Handheld monitors are deployed too. In addition to the winter winds, heavy rain and ice/snow have restricted the works. A relatively calm day in the site compound can be misleading, with very different conditions existing on the bridge structure.

This ornate bridge has a pair of large castellated turrets at each end and smaller turrets linking the spans. The story is that the southern bridge abutment was built on the site of a Saxon burh (fort) erected in 915 by Queen Ethelfleda (or more correctly Æthelflæd, oldest daughter of Alfred the Great and herself ruler of Mercia from 911 to 918) – hence the local name for the bridge. The castellation of the turrets is said to be a nod to that.

All of the turrets have required cleaning and waterproofing. Cast-iron drainage runs from the main turrets to the bearing shelf were also cleared and renewed, in some cases requiring the use of a rope-access team.

A 600kg cast-iron navigation bell, located on the west side of the structure, is to be removed for off-site refurbishment and placement in a public open space. However, removal presented problems because of difficult access. The solution, scheduled to take place on 27 May, is to use a helicopter to lift the bell during an already planned 54-hour disruptive possession.

Meanwhile, down at river level, the timber fenders and associated steelwork that protect the piers have deteriorated and require renewal. This will be accomplished during the summer of 2018 using a specialist barge. Only a narrow time window, between 1 June and 31 August, is available to undertake these works as the intertidal flats and marshes of the Mersey Estuary provide winter breeding grounds for thousands of wading birds.

The barge will be located on spud jacks in the river and will work on the fenders depending on the water level. The works will be planned around the tides and will involve 24-hour working. The fenders are being renewed using sustainably sourced Ekki hardwood – an extremely hard wood originating in subtropical Africa.

Photo: GBickerdike.

Photo: GBickerdike.

Bore

The large tidal range and flow, a feature of the Runcorn Gap, has presented difficulties. The tide rises over a two-hour period each day, but then takes ten hours to go back out again. With the water level ranging from 0 metres to 6 metres in less than two hours, this makes the area a very hazardous environment to work in and around.

Buckingham Contracting has employed Sea Training International to provide site water rescue for both the river and canal locations. This is required whenever any leading-edge works are being undertaken, in order to mitigate the risk of someone falling in.

With quick sand and soft mud exposed when the tide is out and then a tidal bore when the tide comes in, the site teams have needed to be stood down for around 45 minutes each day when carrying out leading edge works. This is because any rescue attempt during that time would be unsafe for the Sea Training International team.

Tight fit

This project has also been made more difficult because of the limited operating space on and around the structure. The team has a narrow walking route along the eastern side of the structure, which has to be used to carry all materials and equipment to site.

The walking route is shared with a third-party cable route carrying an 11kV cable between Widnes and Runcorn, which limits working space further. To ease the burden, the team has designed and fabricated a number of trolleys to move materials along the walkway.

A specialised lifting frame has also been fabricated to lift out the cast iron parapet elements, of which the heaviest is around 400kg. After using the trolleys to transport each cast iron element back to the loading bays at each end of the structure, all equipment and materials are hoisted down to ground level, some 20 metres below. This is a very slow process and involves rigorous lifting techniques to minimise manual handling.

Besides the risk to staff of working next to an operational electrified railway, working at height and within restricted space has been a normal part of the day-to-day challenges that the staff have had to face.

The majority wear harnesses and are clipped on during some of their activities, whilst trained rope-access staff have been brought in to work in otherwise inaccessible spaces, such as the bridge baffles, and to access the outer piers during possession working.

Photo: GBickerdike.

Renewing the timber fenders at water level requires a rescue boat. Photo: GBickerdike.

Consents

During the early stages of the scheme, before works could commence on site, the project had to obtain a number of licences and consents. Runcorn Rail Bridge is a Grade II* listed structure and, due to the nature of the bridge and its location, the consents process took around 12 months.

Approval of the proposed works was also required from the Marine Management Organisation. The Mersey Estuary is a site of special scientific interest (SSSI) and a Ramsar site. It is heavily protected so the pre-works surveys had to be very thorough.

Listed building consent via Halton Borough Council had to be obtained. Licences from Peel Ports for the Ship Canal were also required and it is necessary for Buckingham Group to keep in contact with the Harbour Master each day for ship movements on the canal, during which all works have to be stood down and hot works are not permitted to prevent sparks dropping onto passing ships.

As part of Phase 3 of the project, Buckingham Group is working on the Grip 3 (option selection) approval in principle for the bearing replacement. This work is scheduled to take place in late CP6/early CP7 and will involve jacking up the span structures to access their bearings – clearly an involved undertaking on such an iconic listed bridge carrying the WCML into Liverpool. It should, however, see this great structure fit for another century and a half of supporting the WCML.

Thanks to Will Metcalfe, project manager with Buckingham Group Contracting, for his help with this article.