The job involves shipping more than 4 million tonnes of Crossrail tunnel waste material from three Thames-side wharves to the island.
It is also understood to include extensive earthmoving works at Wallasea Island to create hillocks and dips into which seawater will ebb and flow to attract rare birds such as spoonbills and black-winged stilts.
The succesful firm will be expected to construct the wharves, which will carry enough capacity to handle a steady stream of tunneling waste.
The mud flat and salt marsh habitats created at Wallasea Island will act as a carbon sink and will soak up 2.2 tonnes of carbon per hectare per year.
Transporting tunnel waste by water amounts to a quarter of the carbon cost of road transport.
Requests for further information need to be made by 13 August.