3 November 2011

Costain’s experience in both marine works and nuclear de-commissioning has been recognised once again with the award of a £2million contract to demolish an offshore steel sheet pile barrier wall for client Magnox, at Bradwell, in Essex. 

The barrier wall stands approximately 400m offshore and formed part of the former nuclear power station’s cooling system.  Cold ‘inlet’ water was drawn from the seaward side of the wall and the warmer ‘outlet’ water was pumped out on the landward side, the barrier wall preventing the cold and warm water from mixing. 

Construction work started at Bradwell in 1957 and generation began in 1962.  Power production ceased in 2002.  Following extensive de-commissioning works the site is due to enter a 100-year ‘care and maintenance’ period in 2015. Therafter, final site clearance can be completed.  The site adjacent to the existing Bradwell station has been earmarked by the Government as the location for one of the UK’s new generation of nuclear power plants. 

The two steel barrier wing walls, each approximately 100m long, are separated by a 30m-wide concrete central section.  The sheet piles for the walls were driven 15m into the river bed back in the 1950s. 

“To remove them”, said Hugh Nicholson, Costain Senior Planner, “a barge-mounted long reach excavator will open a diver access trench on either side of the piles.  Divers will then use underwater Oxy-Arc cutting torches to cut the piles into 5m panels, commencing one metre below the existing riverbed level. 

“The final cut to release each 14-tonne panel will be made above the water line, with the load being supported by a barge-mounted crane.  The scrap steel will be loaded onto a barge and taken to a metal re-cycling facility in the Thames.”  Costain and specialist marine contractors Red 7 are co-operating on the project. 

“Touch wood, it should be fairly straightforward,” said Hugh.  “Once the first few panels have been removed we should be through the learning curve, then it is a case of keeping going until all the panels are removed.”  Once the piles are removed, the access trenches can be backfilled. 

Works started in mid-October 2011 and are due to complete in February 2012. 

Environmental considerations have dictated that the works take place over the winter months in order to avoid any potential impact on the local oyster breeding season. 

Ends