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Simon Phillips & Mervyn Dunwoody: Spreading it around

Over 7M.m³ of material will be excavated while building Crossrail. Both client and delivery partner are committed to reusing virtually every particle, but transporting it across London is no mean feat.

With 42km of new tunnel and eight new sub-surface stations to build, Crossrail will produce an unprecedented amount of excavated material − 7.3M.m³ to be exact, which at peak production may require up to 600 lorry loads each day. Generally in the order of 300 loads per day will be moved in the central London section alone.

Since its inception, client Crossrail has been determined to recycle materials but there are few projects that require such enormous volumes. The plan is that up to 2M.m³ will be recycled to be reused as aggregate and hardcore. This still leaves a sizeable amount to take care of.

“Over 99% of material is reusable. The only problem is the sheer volume of it,” says Crossrail construction logistics manager Simon Phillips.

“Over 99% of material is reusable. The only problem is the sheer volume of it.”

Simon Phillips, Crossrail

During the project’s development phase, investigations were carried out by Phillips to determine suitable opportunities for reusing the material in a environmentally beneficial manner.

“I discovered that less than 70km away long-term plans were afoot to construct a Royal Society for the Protection of Birds (RSPB) scheme on Wallasea Island off the Essex coast, which will transform 620ha of arable farmland to coastal marshland. We worked with the RSPB to help realise these plans sooner rather than later.”

Once swathed in marshland and then reclaimed from the sea for farmland, rising sea levels brought about by climate change have placed this site under high flood risk . The RSPB aims to return Wallasea to its former glory by reshaping the land to create a wildlife haven.

Roughly 2.5 times the size of Hyde Park and Kensington Gardens put together, the Wallasea site will require a lot of material to remould it, which is where Crossrail comes in. Clay, gravel and chalk totalling 4.1M.m³ will be transported to Wallasea by ship and the Crossrail team will engineer this material to create the habitats.

“For us, a key driver is meeting our commitment to beneficially reuse the excavated material but clearly delivering cost-effectively is a major consideration,” admits Phillips. “To send that much waste to landfill would have massive cost implications. This site is perfect as it has planning approval and we have engineered a start date that coincides with our construction programme. The scheme will need an awful lot of material. We are sending over 4M.m³ to Wallasea, but it could be twice that amount.”

Reusing materials

Crossrail is currently in discussion with the South East England Development Agency (SEEDA) about two schemes which may use the remaining 1.2M.m³ of materials created during Crossrail’s big build. This will be compacted to create development platforms for two mixed use development schemes in Kent. However, transporting this volume of material from central London to the chosen sites is a major operation.

“A major consideration is to minimise the impact of Crossrail,” says Crossrail Central construction manager for stations, logistics and Custom House Mervyn Dunwoody. “At its peak 200,000m³ of excavated materials will be generated per month. We are planning to limit road transport as much as possible to control the impacts on the road systems.”

“A major consideration is to minimise the impact of Crossrail. At its peak 200,000m³ of excavated materials will be generated per month.”

Mervyn Dunwoody, Crossrail Central

“Another major consideration is keeping the TBMs [tunnel boring machines] moving − this is project critical. We need to ensure they do not stop because materials have not been removed from site in a timely manner.” Pinpointing schemes such as Wallasea that is linked by water and the SEEDA projects near rail terminals avoids the reliance on the road network.

The Thames will be a key Crossrail freight route. Instone Wharf in the Limmo Peninsula and other wharves along the river will be used for shipping excavated material. Located near the eastern tunnel portal where the TBM travelling west begins its journey, Instone Wharf is ideally positioned as the location for transporting material by ship from the tunnelling site.

Materials excavated from the eastern tunnelling drives will be loaded onto ships. It is currently projected that five 2,000t ships supported by barges will travel down the Thames each day at the project’s peak. Rail will be pivotal for transporting material from the western tunnelling drives to the two prospective SEEDA sites. A maximum of four trains of 17 wagons per day would make their journey from Westbourne Park near the western tunnel portal in Royal Oak to the SEEDA sites in Kent.

“Rail freight will be spread across the day to ensure the trains miss peak travel times. Minimising disruption to commuters will require rail planning expertise. Luckily there is no shortage of that across the Crossrail team, which includes Network Rail,” says Phillips.

Finalising routes

Station construction will require road transport for the first part of the journey, in order to link in with the rail and water routes. With station construction programmes beginning before the TBM drives, there is no option to use the conveyor belt route through the tunnels to the water and rail freight facilities.

“We have to use lorry transport at the station sites dotted across central London − it is unavoidable,” says Dunwoody.

Crossrail is working with the relevant local authorities to finalise routes to access station sites and is seeking to minimise disruption. Holding areas for vehicles will be created near each site, to avoid blocking the capital’s main roads. Excavated material will be transported by road to recycling centres which are planned to be located at the wharf sites.

“Overall 85% of materials will be moved by rail or water. The impact on Londoners will be minimised and better still, we will have contributed to a truly sustainable project at Wallasea Island,” adds Phillips.

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