Earth from Crossrail tunnels used for landmark conservation project

Europe’s largest construction project reached another milestone earlier this month when three years of tunnelling work to create Crossrail was finally completed.

Work on creating the high speed rail link that will connect Reading and Heathrow in the west, through new tunnels under central London to Shenfield and Abbey Wood in the east started in May 2009 and is not expected to be complete until late 2018.

But of the myriad construction issues the engineers behind the £14.8bn project had to overcome was what to do with the estimated 7.5 million cubic metres of earth the work to create 26 miles of tunnels under London would produce.

The solution involved a partnership with the RSPB to transform Wallasea Island in Essex into the largest man-made nature reserve in Europe.

The wildlife charity says the Wallasea Island Wild Coast project is a landmark conservation and engineering scheme for the 21st century, on a scale never before attempted in the UK.  

“The aim of this project is to combat the threats from climate change and coastal flooding by recreating the ancient wetland landscape of mudflats and saltmarsh, lagoons and pasture. It will also help to compensate for the loss of such tidal habitats elsewhere in England.”

Moving earth from London to Kent 

Since boring work to create the two tunnels that Crossrail trains will run through started at Royal Oak near Paddington in May 2012, about 5 million tonnes of earth has been transported from up to 30m below the streets of central London to a jetty on Wallasea Island and then on to an 800m conveyor belt.  

The earth from Crossrail's tunnels closest to Essex was loaded directly on to ships near Canning Town in east London, while the byproduct of excavations from the western tunnels was put on freight trains that were then sent to Northfleet in Kent before being loaded on to ships.  

The last of the 2,000-plus shiploads will arrive in 2016, after which the RSPB will source other soil to complete the reserve.  

But long before starts Crossrail transporting an estimated 200 million passengers a year from 2018, a labyrinth of mudflats, mud islands, saltmarshes and lagoons will have been created on land in Kent that used to be two metres below sea level at high tide.

The RSPB points out that because the earth comes from so deep underground, it is not contaminated and will not harm the wildlife that it is intended to help.

The 670-hectare wetland reserve has been designed to encourage birds such as spoonbills, Kentish plovers, avocet, dunlin, redshank and lapwing to breed in the UK as well as providing a haven for Brent geese and curlews in winter.

Saltwater fish such as bass, herring and flounder will use the winding creeks as a nursery, helping the small local seal colony, while the new environment is also ideal for water-based plants including samphire, sea lavender and sea aster.

Although the reserve is planned to be in development until around 2025, the RSPB welcomes visitors “to come along and view the progress as each phase comes to life and the marshland naturally regenerates”.

Image credit: Stephen Richards