Plans for Europe's biggest man-made coastal nature reserve project were officially launched by environment secretary Owen Paterson last week.
The £50m reserve, twice the size of the City of London, will be used to combat threats from climate change and coastal flooding and provide a home for tens of thousands of migratory birds, said the RSPB.
The charity is working with Crossrail, which will deliver 4.5 million tonnes of earth from tunnelling work to help build the nature reserve in Essex. The earth will be sculpted into a wetland landscape of mudflats, salt marshes and lagoons last seen 400 years ago. Contracts for work on the project will be put out to tender at a later stage, a spokesman said.
Contractors will build eight miles of coastal walks and cycle routes and supply plants such as grasses and aquatics. Crossrail has built a jetty and material-handling facility. At its peak, 10,000 tonnes of soil will be unloaded from ships daily.
"This landmark project has never before been attempted on this scale in Europe," said an RSPB spokeswoman. "Wallasea Island on the Thames Estuary will be transformed from farmland into a thriving wetland by 2019."
She added: "Without projects like this, rising sea levels threaten to see another 1,000ha of land lost in the next decade. Wallasea Island will provide 670ha of secure habitat for wildlife to thrive well into the future."
The coalition Government has set a combined target for the re-creation of salt marshes and mudflats of 3,600ha by 2015. The Wallasea Island Wild Coast Project will deliver nearly one-fifth of the total.