Crossing the capital
- Construction ,
- Management ,
- Waste ,
- Pollution & Waste Management
London's Crossrail project is on track to achieve its environment targets. Paul Suff finds out how
Crossrail will link Heathrow and Reading in the west with Abbey Wood and Shenfield in the east, passing through central London and increasing rail transport capacity in the capital by 10%. The full service is due to start operating fully in 2019. Before trains can travel on the route, more than 100km of track will have to be laid, 40 stations built or upgraded and 42km of new tunnels constructed beneath London. The work has significant environment impacts. The tunnelling alone will involve excavating around 4.5 million tonnes of material.
Environment manager Cathy Myatt says Crossrail picked up the baton passed by London 2012 to drive sustainability standards on major construction even higher. “We are certainly pleased with where we are,” she says. “Contractors are exceeding waste targets, with 97% of demolition waste and 99% of construction waste being diverted from landfill, and 99% of excavated material beneficially reused – a large proportion of which is being shipped to Wallasea Island in Essex to create an RSPB nature reserve.”
Myatt also reports some other notable achievements, such as Crossrail’s development of a new BREEAM standard for evaluating the environmental performance of its new underground stations and its requirement that, where practicable, contractors use diesel-powered plant machinery with newer, cleaner engines or retrofit emissions-control devices on to existing engines.
Laying the foundations
Work on Crossrail, which is Europe’s largest construction project, started in May 2009 and most of the tunnelling and major civil engineering works will be completed by the end of this year. From the start, Crossrail acknowledged that the scale of the project meant it could help shape the future of construction, and its aim is to set a new standard for environment management for the industry. That vision, entitled “Setting the standard for environmental performance and leaving the legacy of a sustainable railway”, involves setting high benchmarks for contractors.
“Three-pronged” is how Myatt describes the approach adopted by Crossrail to ensure its environment vision becomes a reality. The first element of that was to put in place measures to ensure the construction works achieve industry best practice across the entire project. “We gathered information on what was currently achievable in terms of waste, for example, and set that out in the works information accompanying companies’ contracts,” explains Myatt. The sustainability team worked with Wrap to set its targets to reuse or recycle at least 90% of the estimated 1.3 million tonnes of construction and demolition waste generated over the main construction period of the project (to 2016), and at least 95% of the 6 million tonnes of clean earth from excavating the new underground stations and train tunnels.
The high standards and targets are accompanied by a strong assurance regime. “We’ve got a system of audits and inspections to ensure contractors are meeting our standards, and robust reporting requirements to provide visibility on how they are performing as the project progresses,” says Myatt.
Above and beyond
Best practice is the minimum level of attainment, however, and the second strand of the Crossrail approach to environment management is to encourage contractors to excel. With contractors generally exceeding the targets for both construction and demolition waste, and excavated materials, many have sought from the beginning to pursue higher standards of performance. “We want contractors to focus on areas where they can realistically ‘push the boundaries’ of what is regarded as best practice. Our ambition is to set the new ‘norm’ in several areas,” says Myatt.
Waste is one such area. Phil Bailey, environment manager at the Hochtief Murphy Joint Venture (HMJV) – the main contractor for the 2.6km tunnel under the Thames that links North Woolwich and Plumstead in south east London and is known as C310 (see panel, right) – summarises the company’s commitment to exceeding Crossrail’s waste targets: “We aim to divert 95% of our construction and demolition waste from landfill and recover all clean and excavated material.”
To reduce waste HMJV is using hoarding made from 100% recycled plastic, which, unlike conventional plywood hoarding, can be reused on other projects. The panels can also be returned to the manufacturer for recycling at their end-of-life. The contractor has also received an exemption from the Environment Agency to reuse tarmac that previously formed the diversion roads at the tunnel entry and exit points at North Woolwich.
Another area of focus for Crossrail is air quality. Non-road mobile machinery used on construction projects is estimated to cause 15% of London’s PM10 particle emissions, a major contributor to poor air quality in the capital. Under its environmental miminum requirements, Crossrail has to implement measures to control emissions from construction equipment, hence the requirement for contractors to use diesel-powered plant machinery with newer, cleaner engines (Euro IIIB standard) or retrofit diesel particulate filters (DPFs) on to existing engines.
Myatt says Crossrail learned from the experience of London 2012 on controlling such emissions and decided to go further. “Also, I knew Crossrail would come under the spotlight if London had a period of poor air quality,” she says. Compliance has not been easy, however.
Bailey reports that HMJV is 100% compliant across the plant where more efficient versions are available or where DPFs can be fitted – it is difficult to fit such equipment to small dumpers, for example.
“More than 20 pieces of plant have either Euro IIIB standard engines or DPFs fitted,” says Bailey. Reaching this position involved HMJV working closely with suppliers to find solutions for different types of plant. He also notes that few hire companies are prepared to invest about £3,000 in fitting DPFs to their machinery unless demand is sufficient.
Crossrail is committed to reducing its carbon footprint during the construction stage and into the future when trains start running. At the start of the project, total carbon emissions for the construction phase were predicted to be 1.7 million tonnes, and Crossrail set a target to lower that overall figure by at least 8%, mainly by reducing the energy contractors consume. Myatt says the project is on track to meet that target.
Again, HMJV is seeking to go further, this time by reducing carbon emissions by 10%. Bailey says the measures introduced by HMJV include use of:
- hybrid mobile elevating work platforms (MEWPs) and lighting towers, which emit 94% less carbon compared with conventional MEWPs and towers;
- “eco-cabins”, which are fitted with motion sensor lighting and double glazing;
- LED site lighting; and
- early connection to the grid to reduce generator use.
To encourage those working on the project to identify improvements and solutions to problems, Crossrail operates its Innovate 18 programme. “It’s about helping Crossrail to be better, but it’s also about the project’s legacy,” says Myatt. Ideas that are accepted are also eligible for funding to develop them. These include the trial of low-carbon concrete in the reconstruction and refurbishment of the Connaught tunnel, a 550-metre link between Royal Victoria Dock and Royal Albert Dock in east London, which dates from 1875 and was closed in 2006. Another is the reuse of excavated clay as an aggregate.
Myatt also points out that many contractors have implemented initiatives to save water, although Crossrail has not set a target. At Whitechapel station rainwater is captured on the operating platform and gravity-fed via a sediment interceptor into retention tanks for reuse. On the C310 tunnel, HMJV is reducing its use of potable water for tunnelling operations by using surplus groundwater from a dewatering scheme, saving more than 2 million litres a week.
The final component of the Crossrail approach to environment management is “sharing” across the project. “All contractors have to be certified to ISO 14001 and employ an environment manager,” says Myatt. She explains that these requirements have the benefit of creating a community of environment practitioners across the project, which has helped to establish a cooperative culture. ‘We get them all together every other month to discuss issues,” she adds.
Crossrail has also installed a member of its environment team to work alongside contractors in their main site offices. “It’s the first project I worked on where you’ve got the client and contractor working in the same office,” says Bailey. “Their presence keeps you on your toes as they can see what you’re doing, but they can also be a great source of help.”
Bailey explains that Crossrail checks all section 61 prior consent applications before they are sent to a local authority. “Crossrail provides a level of assurance and we work with its environment team to ensure all s61s are up to standard. Having that assurance available is good for us as it can take up to six months to get everything together for a big consent application,” he says. Bailey finds that councils often turn the applications around relatively quickly because they know Crossrail has already examined them.
Myatt says the close client-contractor working relationships aid coordination. She gives the example of where several contractors are working in one location, which, unless activity is carefully coordinated, can exacerbate environmental problems, such as noise. “At these sites, we’ve put in place cumulative noise management plans to identify the combined noise impacts so we can take steps to reduce the impacts on the local community.”
Close cooperation is also the hallmark of how Crossrail and its contractors work with local authorities and the Environment Agency. “We have a single point of contact at each of the two councils [Greenwich and Newham] in the areas where we’re working as well as at the agency,” says Bailey.
“It’s easier to keep one person in the loop. When the tunnelling machine broke through at North Woolwich, for example, I was in daily communication with the council contact in Newham, so they knew what we were doing day to day.”
Positive environment message
A key goal for Crossrail is to promote a positive environmental culture throughout the project and put in place the legacy of an environmentally aware workforce. Crossrail’s “Greenline” recognition scheme and environment awards support this objective, rewarding individuals and teams on construction sites who go beyond their normal job requirements in tackling environment issues and encouraging positive behaviour.
The Greenline scheme, Myatt explains, is aimed at communicating environment information to everyone on the project to provide the knowledge of what needs doing and the motivation to get involved. “It demonstrates that the recipient has shown high-level commitment to the environment through leadership and guidance, and in their decision-making,” she says. HMJV has achieved Greenline status. Bailey says such recognition will help HMJV when it tenders for future contracts.
Driving up environmental standards across the industry so that future major construction projects, such as HS2, start from a higher level is the underpinning objective for Crossrail. As Myatt says: “The next project will hopefully build on what Crossrail achieves and take environment standards a step further.”
Two types of tunnel boring machines (TBMs) are used on the Crossrail project to reflect the differing ground conditions along the route. The Thames Tunnel (C310) is bored mainly through chalk, so slurry TBMs, named Mary and Sophia, are used, whereas earth pressure balance machines are deployed elsewhere because the ground is predominantly London clay, sand and gravels. Each of the eight TBMs used on the project are operated by a team of 20.
Across the 42km of tunnels, the TBMs will excavate 4.5 million tonnes of material, and install 250,000 pre-cast concrete tunnel segments to form the lining. The 2.6km tunnel C310, which links North Woolwich and Plumstead, is being bored about 15m below the river bed. Mary and Sophia are 110m long, weigh about 980 tonnes and drill at a rate of 100m a week.
Hochtief Murphy Joint Venture (HMJV) is the main contractor for C310. Environment manager Phil Bailey says HMJV is committed to preventing pollution and minimising the negative impacts of construction work. “HMJV aims to go beyond environmental compliance and meet best practice across all activities,” he says. Achieving its environment objectives requires HMJV to innovate. An example is its proposal to increase the size of the pre-cast tunnel segments, so fewer need to be shipped from the manufacturer in Ireland. “Making the segments slightly larger means the overall number that will be installed across the project is reduced by 7%,” explains Bailey.
Material (80% of which is chalk) excavated by Mary and Sophia is piped back as slurry to the C310 base at Abbey Wood where there is a separation treatment plant. After being separated from other materials, chalk passes through a filter press. This squeezes out the water and compacts, or presses, the chalk into “filtrate cake” at the rate of 15 tonnes an hour. These cakes have a moisture content of less than 35%.
A large proportion of the excavated material from the Crossrail project will be used to create a huge wildlife reserve at Wallasea Island, eight miles north of Southend-on-Sea, which the RSPB will transform into 1,500 acres of tidal wildlife habitat. The chalk from C310 is not suitable for Wallasea, so most of the material from that tunnel will be transported to Veolia’s Pitsea landfill facility at Holehaven Creek to help transform the site into high-quality land for public access and a chalk-grassland habitat.
The other excavated materials, such as gravel, are transported to a washing and grading centre at Tilbury for separation. Larger aggregate is sold for use in the construction industry, with finer graded material sent for use in landfill restoration.
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