Wallasea Island – infrastructure working on behalf of conservation

As the country’s infrastructure continues to develop, it’s vital that we ensure our natural environments, and the wildlife they contain, are protected. With this in mind, the UK’s developers are now being asked to make their projects more environmentally responsible and engaging for the general public. This is what the Crossrail team has been able to do by using spoil from the tunnel excavations to help create a new island and bird sanctuary on the banks of the River Crouch at Wallasea. Declan Burns of ESG explains how this was achieved.

Saltmarsh at Wallasea Island. Credit: Ben Hall,

Dealing with a mountain of waste

To cope with London’s ever increasing population, the Crossrail project was designed to increase capacity across the capital’s rail network. By 2018, the scheme will have created 42km of subterranean tunnels, as well as nine new stations. Needless to say, a construction project operating on such a great scale, generates an enormous amount of waste. Due to the extraordinary size of Crossrail, the tunnel boring machines (TBMs), operated by Joint Ventures, have unearthed around six million tonnes of spoil as a by-product of the works.

The problem which faced developers was how to address the colossal amount of waste material in a legal, safe and environmentally responsible manner. After hearing about the Royal Society for the Protection of Birds’ (RSPB) Wallasea Island Wild Coast project, a ground breaking conservation scheme in Essex, and the largest of its kind in Europe - the Crossrail team decided to put their waste to good use.

“We’re keen to complete the Wallasea Island Wild Coast Project by 2025. To do this, we still need around eight million tonnes of clean soils. “We’re interested in speaking to any supplier who can provide reasonable quantities of material by ship to our jetty at Wallasea. If you think you’re able to help in this way, please do get in touch" -Chris Tyas, RSPB

From spoil to soil

To construct the new subterranean passageways, the TBMs, each weighing nearly 1,000 tonnes, and measuring seven by 150 metres, started digging in November 2012.

To help with the tunnelling process, which uses polymers to facilitate the handling and management of the waste soils ESG was brought on board by Atkins to contribute to the assessment of the potential environmental impact of the tunnel spoil. The aim was  to ensure that the waste was safe for relocation to Wallasea Island and other land redevelopment schemes. The company developed methodologies to determine the concentrations of the polymers within the excavated soil following biodegradation.

In order to pass strict environmental controls, the soil then had to be tested for key chemical parameters such as asbestos, cyanide, aromatic hydrocarbons, arsenic, and cadmium. If significant amounts of these contaminants had been present, they could have resulted in environmental issues for the spoil’s intended location, such as toxicity, carcinogenicity, polluted water or stunted plant growth.

Following the completion of ESG’s analytical activity, and then a robust assessment, the excess Crossrail spoil was declared legally compliant and safe for re-introduction into the environment.

A collaborative approach

Throughout the relocation process, the Crossrail team, Atkins, Living Ventures and ESG’s Multi-Sector Services team, collaborated effectively to help ensure that just over three million tonnes of waste material was safe to be shipped to Essex via the RSPB jetty at Wallasea. The toxin-free soil was then distributed to help create the Wild Coast project. In order to see the project through to completion, the RSPB still needs an additional eight million tonnes of clean soils, ideally from a range of large-scale construction projects.

Wallasea: a new home

Once completed, the RSPB reserve will provide a haven for a wide range of nationally and internationally important wildlife, and a spot of natural beauty for the local community. The conservation scheme has recreated the ancient wetland landscape of mudflats, saltmarsh, lagoons and pastures, which provide a natural flood barrier for England’s eastern lowlands.

Wallasea is now home to a range of native UK birds, which change throughout the year. In spring, it is home to breeding waders, oystercatchers and the highly acrobatic redshanks. In summer and autumn, visitors will be able to watch the flowers and butterflies come into their own, as well as ringed plovers, dunlins, curlews, and greenshanks. Of all the seasons, it’s winter in which the sanctuary contains the most amount of wildlife, with wigeons, brent geese and golden plovers being in abundance.

Balancing responsibilities

Through its Biodiversity 2020 Strategy, the Government has set itself the target of halting the overall loss of England’s biodiversity by 2020. However, the UK’s population is expected to increase by over four million in the same time period and many groups, such as the Institution of Civil Engineers, is calling for any future government to prioritise infrastructure spending and development to support this growth.

New major projects including the £15bn roads investment strategy are making their way through the construction pipeline. It falls on the developers working on these projects to take charge of their environmental responsibility to support the Government’s Biodiversity 2020 strategy, while still meeting the country’s demands for improved infrastructure.

Through a remarkable feat of engineering and by making use of cutting-edge science, the team behind Crossrail, Europe’s largest infrastructure project, and its contracting Joint Ventures, has proven that this is certainly achievable.

RSPB’s Chris Tyas, RSPB Wallasea Island project manager, commented: “We’re keen to complete the Wallasea Island Wild Coast Project by 2025. To do this, we still need around eight million tonnes of clean soils. The Crossrail project has provided a perfect example of how the construction and conservation industries can work together to achieve fantastic results.

“We’re still interested in speaking to any supplier who can provide reasonable quantities of material by ship to our jetty at Wallasea. If you think you’re able to help in this way, please do get in touch:

Declan Burns is managing director, Multi-Sector Services, ESG