Barrett Byrd Associates

Plans for a new River Mersey road bridge in Halton would not only remove congestion from the existing Runcorn to Widnes link but is also key to increased regional prosperity. Claire Symes reports.

Big is the only way to describe plans currently being developed by the Mersey Crossing Group (MCG) and consultant Gifford for a new road bridge over the River Mersey. The project is not only the largest local authority transport scheme in the pipeline but the £335M bridge itself will probably be the longest constructed in the UK in recent years.

Realisation of this major scheme would remove a bottle neck around the existing Silver Jubilee Bridge between Runcorn and Widnes (see box) which currently carries over 90,000 vehicles a day. Around 80% of the traffic using the existing bridge is through traffic which could be better served by a new bridge with better connections to the regional road network.

“The Silver Jubilee Bridge is over capacity and is not only a bottle neck to traffic but is also restricting economic development within the region,” says MCG chairman and Halton Borough Council (HBC) leader Tony McDermott. “Construction of a new bridge is essential to future economic growth and will have a big influence on traffic flow in the whole region.”

Need for a new bridge crossing over the Mersey was first voiced in the early 1990s. HBC chairs the MCG which is a consortium of local authorities and business interest groups who have joined together to campaign for a new bridge.

MCG appointed Gifford as lead consultant in July 2001 to oversee and champion the project from concept through to completion. The project has just reached a milestone with delivery of the design submission, as part of HBC’s Local Transport Plan, to the Department for Transport in a bid to gain government approval and funding for the scheme.

“Over the last two years we have headed up a team of over 20 specialist consultants who have worked on developing detailed plans for the scheme,” says Gifford director Ian Hunt. “The study looked at all the environmental, social and economic impacts of the various route and design options and also included public consultation.”

In April this year the route for the span was chosen and will bypass residential areas close to the Silver Jubilee Bridge. The New Mersey Crossing will join the Central Express Way in Runcorn to the south with the A557 in Widnes to the north. The span is 2.5km up stream from the existing bridge and will carry the new road over the River Mersey’s tidal estuary and the Manchester Ship Canal.

“Construction of the new bridge will allow the Silver Jubilee Bridge to be used solely by local traffic and provide proper facilities for pedestrians and cyclists,” says Gifford engineer Sas Fernando. “The narrow dual lanes of the existing layout means that pedestrians have to use a very unwelcoming footbridge suspended off the main structure and cycling across the main bridge could be viewed as an extreme sport.”

Local public support for a new road bridge in the area is almost overwhelming with 97% in favour and more than 70% backed the route currently being developed.

Gifford’s proposal for the new bridge includes three 360m cable stayed spans supported by three 110m tall towers and a consistent deck construction throughout to suit either launch or cantilever construction. Structural strength of the bridge will come from the extra deep deck design with pierced webs to give the bridge a ‘lighter’ appearance.

“The 7m thick deck will allow a dual deck to be incorporated which would create the potential for a separate footpath and cycle path on the lower section,” says Hunt. “There would also be room for a light rail system to be carried on the lower deck which would simplify development of any future extension to the existing Liverpool network.”

Concept design also envisages that centrally mounted cable stays will be used to suspend the deck and maintain navigation heights at high water in both the Mersey and the adjacent Manchester Ship Canal. The deck will carry a two lane dual carriageway with hard shoulders that will give scope for widening the crossing to a three lane dual carriageway in the future.

Complex geology and sensitive ecology have greatly influenced the overall design and route selection. “Crossing the Mersey downstream of the Silver Jubilee Bridge was ruled out in the early stages because it is a haven for wading birds and is designated as a Special Protection Area and Site of Special Scientific Interest,” says Fernando. “The preferred route has been selected on the basis that it will cause the least impact on the environment and estuary dynamics.”

Foundations for the piers on the southern bank are straightforward and can be founded in the competent sandstone bedrock. But on the northern side, the site is underlain by a thick layer of Glacial Till over the sandstone which is a know aquifer on the northern side.

“Piers on the northern bank will have to be founded in the Glacial Till because much of the area has been used by heavy industry and piling through to the sandstone aquifer could create a pathway for contaminants,” says Hunt. “Piers within the river channel will be supported in the sandstone but hydrological investigations have shown there to be little contamination in the estuarine sand banks, so present little environmental risk.”

Economic studies carried out present some compelling data and suggest that the new bridge could help create more than 3000 jobs, add £85M to the local economy each year and increase property prices. Estimates also indicate that over 30 years the new link could save around £1000M in reduced journey times alone.

DfT’s initial reaction to the plan is expected in December this year and, according to Hunt, the decision could go either way. But if the plans are given the green light and allocated government funding, construction work on the three year build could begin in 2005. “It would be an ambitious but not impossible programme,” says Hunt. “Plus the opening date would tie in with Liverpool’s year as European City of Culture in 2008.”

BOX

Bridging the Runcorn Gap

Building a road crossing between Runcorn and Widnes has been a challenge against which many engineers – including Thomas Telford – have pitted their wits over the years. Despite the numerous proposals only two road links have ever been built between the two towns – the UK’s first transporter bridge and the existing Silver Jubilee Bridge.

At just under 500m the Runcorn Gap is one of the narrowest points in the Mersey Estuary and this logical crossing point has been the site of a ferry since the 12th century. Plans for a road crossing at the Gap date back to the early 19th century but lack of finances and the need for a large navigational headroom meant these plans were doomed to failure.

First fixed crossing across the Gap came in the form of the Ethelfleda Rail Bridge which opened in 1868 but work on a road crossing did not begin for another 33 years. Construction of the Manchester Ship Canal in the 1890s parallel to the River Mersey further complicated matters for ferry passengers. The new canal ferry crossing had to be completed using two boats and passengers had to scramble over the canal’s gantry wall between the two boats.

Work on the transporter bridge – a gondola suspended from an overhead rail running between towers on both banks – began in late 1901 and carried its first passengers in 1905. The high level rail allowed the gondola to be carried 4m above high water level but maintained the navigation height in both the Mersey and canal.

The structure was dogged with a poor safety record and reliability problems. This, combined with increasing volumes of motorised traffic, fuelled demand for a permanent road link in the 1930s. But drivers had to wait until 1961 for their wish to be granted in the form of the Runcorn Widnes Bridge which was later renamed the Silver Jubilee Bridge after it was refurbished in the 1970s.

The new bridge’s steel truss arch was the third largest in the world when it opened and carried around 9000 vehicles per day on its dual lane deck when it opened. Traffic volumes continued to increase and the deck was modified in the 1970s to carry two lanes of traffic in either direction.

Today the Silver Jubilee Bridge has reached its maximum capacity with around 90,000 vehicles using the crossing each day.

Back