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29th March 2015 | Today's High Tides | 08:25 - 3.90m | 21:02 - 3.82m | Full Tide Tables

Wallasea Wild Coast

The RSPB’s Wallasea Wild Coast project has reached an important milestone, with the completion of the operation to ship tunnelling spoils from the London Crossrail project into the site.

Crossrail has been the amazing project to create a new, largely underground, railway across London, the largest civil engineering challenge in Europe, with a cost of over £15 billion. At Wallasea a new ship unloading pontoon was installed and since August 2012 some 2.9 million tonnes of clay and other tunnelling materials have been imported into Wallasea Island, being carried round from R. Thames in a fleet of seagoing ships. Each ship carries over 2,000 tonnes of material, and there have been up to six ships engaged in this trade at a time.

The tunnelling under the centre of London has been an incredibly complex operation, working in some places extremely close to existing buildings and threading its way through the network of existing underground railway and other tunnels. However the work has gone very quickly and with few problems, so that the major ‘civils’ are now substantially complete. The ships are presently clearing the remaining stockpiles of material at the wharves at Northfleet Kent and Barking Creek. There will be comparatively small amounts to deliver in early 2015 while the work goes on to install railway and signalling systems and finish the huge station caverns which have been excavated.

The Wallasea Wild Coast Project was designed to create a major new wetland habitat for migrating waterbirds and wildfowl, the largest of its kind in Europe. The previously low lying island is being reshaped by the import of material before the sea walls will be breached to allow the R. Roach to flow into and out of the island. This work is being carried out in a phased way, the island being divided into five ‘cells’, each providing  varying conditions and habitats carefully designed for different birds and creatures.  The project was designed so that Crossrail would provide sufficient material for ‘Cell 1’ – the largest of the cells which is towards the eastern end of the island. There will eventually be six deliberate breaches of the seawall, of which the first three will be into ‘Cell 1’. Breaching of the seawall is obviously the last major item of work for the completion of each cell, and the breaches into ‘Cell 1’ were originally planned to take place in 2016, but Crossrail’s tunnelling work has gone so smoothly and quickly that the breaching into ‘Cell I’ has been brought forward, the intention now being to breach the seawalls in July 2015.

Although the complex tunnelling work went very smoothly, problems were encountered at first in being able to transport the heavy and sticky London Clay along the conveyors into Wallasea Island. While work was done to modify the hoppers and conveyors some material had to be disposed of elsewhere so that the huge tunnelling machines were not held up. That has meant that the design of ‘Cell 1’ has had to be  modified to use slightly less material, and some material has had to be taken from ‘Cell 5’ in order to complete ‘Cell 1’.

It was always known that Crossrail would not provide enough material to complete the Wallasea Wild Coast Project, and that other sources of material would have to be found. The RSPB now needs to identify sources for about 4 million tonnes more of suitable material. Possible sources include the Thames Tideway Tunnel (the major tunnelling project to capture all of the storm overflows from the many sewage works in Central London), and the groundworks for the possible ‘Sizewell C’ atomic power station on the Suffolk coast. It may be also that ‘HS2’ – the government’s promised High Speed rail line from London to the North might generate large quantities of material which need to be disposed of for re-use in a project which will generate massive environmental benefit.  Other possibilities might include major port dredging projects. At present however no definite source has been identified.

The original planning consent for the Wallasea Project was for completion by 2019, and the unloading jetty in the River was to have been removed by then. That planning consent has now been extended to 2025. It is likely that when Crossrail’s material is finally expended the unloading pontoon may be ‘mothballed’ until another major capital engineering project comes on-stream  needing  to take advantage of the unused capacity in Wallasea Island. With the notable exception of the problems getting the sticky clay along the conveyors, which have largely been overcome, the Wallasea Shipping operation has worked very smoothly, with not a single marine problem or incident throughout, and because of the patience and tolerance of other river users there has been a minimum of disruption or inconvenience to leisure boating activity. Wallasea has been demonstrated to be a project that really works and we firmly believe that it is not a question ‘If’ the Wild Coast Project will be completed, – merely a question ‘When?’