Sustainability underpins our work. From the start of a project we aim to turn it into an opportunity for growth, and to maximise sustainable outcomes for the environment and the local community. By taking cars off roads, metros are essential to reducing greenhouse gas emissions and improving air quality in urban areas.
But building infrastructure in already congested cities can generate a huge carbon footprint and environmental damage.
Concrete is the major source of carbon on tunnelling projects. Our engineers work continually to make tunnels more sustainable.
On the Northern Line extension (NLE) being built in London, our engineers worked with contractors FLO – a joint venture between Ferrovial and Laing O’Rourke – to identify potential resource and carbon savings. They found that reducing the thickness of the segments lining the walls of the tunnels from 280mm to 250mm would save about 2700m² of concrete and 1500t of carbon.
Replacing ordinary Portland cement with alternatives, such as ground-granulated blast furnace slag (GGBS) from steel manufacturing, produces concrete with lower embodied carbon. On the NLE, we used concrete for secant piling with 95% GGBS – much higher than the norm. It reduced embodied carbon by 80% compared with conventional Portland cement. The slag-based concrete was carefully designed to optimise the performance of fresh and hardened concrete, including its long-term durability, and minimise the environmental impact.
Adopting a more sustainable approach has financial as well as environmental benefits. As part of our multidisciplinary design role for Crossrail on the Elizabeth Line in London, we collaborated with manufacturers and future asset operators on LED lighting for new underground tunnels and stations in the central section. LEDs will produce significant whole-life cost and carbon savings compared with conventional lighting – £2.4M in energy savings and 23,400t of carbon.
Quantifying emissions avoided with Moata Carbon Portal
To ensure sustainability initiatives are captured, we have developed a sustainability and innovation database. It includes the estimated cost, time and carbon savings achieved on a project. Meanwhile, our Moata Carbon Portal tool is the first calculator to measure the lifetime capital and operational carbon footprints of BIM-designed assets.
Moata Carbon Portal was introduced when the NLE was at the technical phase of design (RIBA stage 3/4). Moata Carbon Portal is normally most beneficial at the optioneering stage of a project, but we were keen to use it to quantify the amount of carbon avoided by our design solutions. Using Moata Carbon Portal enabled us to process whole designed assets – such as Battersea Station - in one go.