Above the Standard: HOCHTIEF at the “Crossrail” Project in London

In ever-expanding cities across the world, city planners are rethinking their transportation policies and setting their sights on sustainable mobility. In spaces that had been allocated to cars, people are now the focus. People and the environment benefit from expanding bicycle path networks, car-sharing services, and better local public transport connections. A look at London shows where we are heading – and that HOCHTIEF is a safe companion on this path. In the UK capital, the international construction company is making a key contribution to a highly sustainable tunneling project.

“Crossrail” is a new 118-km rail line from west to east offering access to Heathrow Airport. It is currently one of the largest transportation infrastructure projects in Europe: More than 10,000 engineers and builders have been feverishly working to build 10 new stations and drill 42 km of tunnels.

In a joint venture with J. Murphy & Sons, HOCHTIEF has been a key partner in one of the most demanding lots. In June 2015, the team completed – on time and within budget – the construction of the almost 3-km-long tunnel section C 310, which leads from Plumstead, underneath the Thames River, to North Woolwich. With the construction of the two tubes – each having an outside diameter of more than 7 meters – the team provided an impressive performance not only with regard to engineering, but also in economic, ecological, and social terms.

“Sustainable aspects are gaining in importance, particularly for major infrastructure projects, and are having an increasing influence on the awarding and execution of projects,” says Riku Tauriainen, who led the Crossrail project on behalf of HOCHTIEF. Especially in London with the Crossrail project, the client demanded very high standards. Because of their many years of experience, the tunneling experts were well prepared.

Energy demand on construction site greatly reduced

Since the beginning of the C 310 project in early 2011, the team had focused on reducing emissions at each work site. As an example, they saved 80 percent of the energy demand for construction site lighting. The site was equipped with LED lights, which require considerably less energy than conventional light sources. In addition, materials and excavation materials were recycled, transport durations were significantly reduced, and new technologies were used. By optimizing construction workflows, employees reused some 1,200 tons of material. The performance of occupational safety and health standards were also optimized.

When installing the inner shell of the tunnel, a difference of only 10 cm may mean monetary savings of thousands. HOCHTIEF adapted the width specified by the client of the formwork segments – referred to as “tubbings” – from 1.5 to 1.6 meters. This idea resulted in an entire chain of positive effects. First, the volume of segments that had to be produced, transported, and used was reduced by 7 percent, reducing CO2 emissions and costs accordingly. Underground, where the two tunnel-boring machines “Sophia” and “Mary” worked around the clock, the installation of a total of 3,405 concrete rings went considerably faster. Due to the lower number of segments, there are now fewer connection joints between segments, and thus fewer possible “weak points” in the tunnel. The project team gained several working days in this way.

Groundwater recycled and reused

In terms of conserving resources, employees also had effective ideas. For example, since groundwater had to be removed from the excavation site, tunnel experts collected the water and recycled it. Combined with collected rainwater, it was used in propulsion, in bentonite recycling, and as a spray liquid as well as for mortar preparation. Thus, the team saved 2 million liters of drinking water per week – 68 million liters during the entire project: an amount that would fill 27.2 Olympic swimming pools! For this achievement, the joint venture was awarded a prize in the category of “Innovation and Environmental Performance” by the client. It had specifically promoted and called for sustained acting through internal competition.
The tunnel team used the opportunity to ask for sustainable ideas internally as well.

The “Green Idea Tree” was consequently created in order to continually improve ecological efficiency. The best proposals were awarded and implemented. One of these ideas was to dry the lime sludge taken from the Thames River underground during the early phases of the project. This procedure made it possible to use the sludge again as environmentally friendly material in other projects. Other excavation materials were used to replenish and to redevelop the building site. A total of 3 million tons of excavation materials from the Crossrail project were shipped to Essex in order to create a bird sanctuary in a river delta. Transporting the materials by ship – a total of 1,528 charges – was the best low-emissions alternative and served to avoid numerous truck trips through downtown London, which already experiences heavy traffic volumes. The habitat will provide a safe home to tens of thousands of domestic and migratory birds and will have a pronounced balancing effect on the wildlife.

Employees engage in social projects

Aside from environmental issues, the team at lot C 310, led by project manager Riku Tauriainen, also took into account social aspects. In addition to constant exchanges with local residents, employees did volunteer work. They organized transport services for seniors to go shopping, repainted Salvation Army accommodations, and collected debris by hand in an adjacent public park. After both tunnels became accessible, residents were allowed to explore them in an open house of sorts.

The installation of the tracks and the building of stations began in 2015. The first trains will travel through the tunnel in 2018 and transport thousands of people daily. HOCHTIEF has made its lasting contribution to this project as well as to its vision: “HOCHTIEF is building the world of tomorrow.”