Wisbech flood defence scheme scoops top award and is now on course for national accolade

PUBLISHED: 16:09 11 May 2015 | UPDATED: 16:09 11 May 2015

Freedom Bridge, Wisbech. Retaining Wall.

Freedom Bridge, Wisbech. Retaining Wall.

Archant

The ambitious five-year scheme to improve Wisbech's flood defences along the River Nene has won a prestigious regional award.

Cambridgeshire County Council’s scheme to improve the retaining wall, carried out under contract by Skanska and Breheny, picked up the infra-structure award at the annual RICS Awards East of England held at The Apex in Bury St Edmunds.

It will now go forward to the RICS Awards Grand Final on October 16 at the The Dorchester Hotel, London.

The Freedom Bridge retaining wall project, a 313m flood defence scheme was completed last February and addressed the shortcomings of the pre-existing structure whilst also increasing flood defence levels to protect the town centre even allowing for global warming.

A supporting statement submitted by Skanska as part of the project’s competition entry stated: “The River Nene posed some significant risks during construction as it’s a deep, fast flowing navigable river with a tidal range of approximately 6m.”

It also pointed out: “The structure retains the B198, one of the main arterial routes into the town centre, and comprises steel sheet pile and reinforced concrete walls tied back to buried anchor blocks. The retained height is up to 7m and the existing steel parapets form part of the town’s flood defences.”

Additional funding was found for the £2.841 million project after completion of Phase 1A to improve the streetscape after feedback from Wisbech Town Council.

The project team engineered a solution to retrofit brick slip cladding and coping units to the reinforced concrete parapet to enhance its appearance. Bricks were chosen to match the previous flood defence works in the area and provide continuity along the river front.

The four years of work saw no injuries or incidents being reported.

Early contractor involvement led to a change in the way part of Phase 1B was carried out with Skanska proposing an alternative solution to remove the weak cantilevered footway so a new one could be built. Skansks proposed constructing a new steel sheet piled wall in front of and tied into the existing retaining wall.

This improved health and safety and environmental aspects on site by eliminating the need for workers to use temporary platforms suspended over the river.

It also minimised construction waste and disposal as the concrete cantilever was recycled on site and used to backfill the void behind the sheet piling.

It also reduced construction costs, length of programme time and the need for future maintenance.

Pile driving had to be carefully monitored to limit the likelihood of damage occurring to adjacent properties especially as some were listed buildings through noise and vibration.

The east coast tidal surge of December 2013 caused damage to temporary works collapsing two panels of brick in the process, but due to the rapid response of the site team the river did not breach the temporary flood protection measures and the site perimeter was secured to stop members of the public accessing it to watch the surge.

Once the Phase 1D wall was completed the redundant flood defence was removed and the 3m wide strip of land in between was landscaped and opened as green public space.

Steve Dighton, business development manager for J Breheny and former bridge manager for Cambridgeshire County Council, said: “This is a great result for everyone involved. From the outset it was going to be a 10 year project, but was condensed down to five years and there is now one final phase to complete this summer. What is offers for Wisbech now is a one in 200 year protection for flood risk rather than the previous one in 50 year protection.”

He explained the project was completed despite numerous constraints including the seven metre tidal rise and fall of the Nene - the third largest in the UK.

“Trying to complete everything with such a constraint was a real challenge especially in terms of traffic and road closures and for the projet as a whole,” he added.

Mr Dighton said the project had resulted in numerous other benefits for Wisbech including street improvements, re-piling of the retaining wall, new flood protection wall which also services as a vehicle restraint, new paving and cycleway.

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