Clay, chalk, sand and gravel waste material will be transferred by ship to Wallasea Island where it will raise the ground level of the island helping to create 607ha of tidal wildlife habitat. The material will create hillocks and dips into which seawater will ebb and flow.
Faber Maunsell Aecom is designing the wetland, the largest scheme of its type in Europe. Marine environmental consultancy ABPMer will examine hydrodynamics and environmental impacts.
Faber Maunsell Aecom associate director Philip McLoughlin said: "The spoil from Crossrail will raise the land and different levels will create different habitats – mudflats, salt marsh and intertidal."
The area is so large that the material from Crossrail will only provide approximately two fifths of the fill required. This amounts to an estimated 3M to 4Mm3 of the 7.5Mm3 total fill that the project needs.
The RSPB will submit a planning application for use of Crossrail fill next week, and a public consultation will start in December. Essex County Council is expected to reach a decision in the spring. Work on Wallasea is expected to start in Autumn 2010 and will take between five and 10 years.
The cost of the project has increased from an initial estimate of £12M and Crossrail is making a significant contribution to the cost of the project.
"This is a ground-breaking deal between one of the UK’s leading companies and an environmental charity," said RSPB chief executive Graham Wynne. "It is absolutely wonderful news for wildlife."