During construction of London’s landmark Crossrail, more than three million tonnes of spoil has been excavated from beneath the capital and shipped to Wallasea Island to create Europe’s largest man-made wetland.

AECOM has carried out the design of the site earthworks for this ambitious conservation project, which will help to replace the marshland lost along the Essex coast. The created habitat will include salt marshes, mudflats, salt marsh pools, water creeks, lagoons, grazing marshes, seawalls and bunds.

As Wallasea Island is two metres below sea level, various embankments and earthworks are to be built around the site, using the earth excavated from Crossrail. During excavation, it became apparent that there was less waste material than anticipated. AECOM’s ground engineers, working closely with the Royal Society for the Protection of Birds (RSPB), were tasked with redesigning the site earthworks, using the redesign to enhance the ecological value of the island, providing a diverse range of new habitats whilst ensuring the tidal flow of water on and off the island would be managed.


Patrick Cox