Costain sees benefits of production-thinking approach

Applying modern methods of construction to a complex tunnel fit-out project helped Costain mitigate a predicted 72-week programme overrun, improve safety and sustainability, and reduce quality issues, Simon Gilmour, head of design, told GIRI’s members' meeting. 

Costain operates in the economic infrastructure sector and Simon says the company talks about ‘production thinking’ rather than modern methods of construction. “We take a more holistic approach, and MMC is only a part of it. It is something we are pushing hard. Our CEO has said this is top priority for Costain in 2024.”

To demonstrate the benefits of this approach, Simon shared a case study of a Crossrail tunnel project that Costain worked on in 2013. The logistics of the tunnel meant that aspects of the fit-out design were problematic to deliver, in particular the emergency passenger walkway. “Our tender assumed we could achieve a rate of 200 linear metres a day. Once we developed the logistics plan and installation methodology for the walkway, the best we could achieve was 60 linear metres a day. This would have seen the project overrun by 72 weeks.”

The initial design for the walkway that Costain inherited was for a metal bracket with a pre-cast concrete plank on top, but a combination of factors made this impractical. “The concrete cassette was too bulky – we couldn’t get enough of them into the tunnel at a time – and difficult to lift safely. The ‘stick build’ metal brackets were too slow to assemble. The walkway itself clashed with the track-laying train, which had a bigger gauge, and the design would have required us to drill 250,000 fixing holes into the tunnel.”

Rather than proceed with this design, Costain applied a production-thinking approach to the problem and replaced the concrete plank with an aluminium one, which was smaller and lighter – just 10kg compared to half a tonne. “We didn’t need any special lifting equipment, so it was safer. We also preassembled the walkway bracket and put other services on it, and it sat on adjustable arms so we could fold it out of the way of the tracking-laying rolling stock to avoid damage.”

A standard bracket arrangement also allowed Costain to use an automated drilling ‘robot’ to drill the 250,000 fixings in the tunnel lining. To overcome the challenges of drilling into the tunnel segments, Costain had to 3D scan the entire tunnel, convert this into a 3D CAD model, and create a flexible design bracket. This had multiple pre-form fixing holes and worked in multiple fixing arrangements. The drilling robot had 20 pre-assured drill pattern design to choose from and produced its own ‘as drilled’ information for O&M records. Wi-Fi was installed in the tunnel to enable the robot to geo-locate and reference itself against the 3D model.

Not only did this solution claw back the 72-week overrun and improve quality, but it also led to significant sustainability gains. “We reduced concrete use by seven tonnes and saved 670 tonnes of CO2e.”

Simon believes this project encapsulates what Costain terms production thinking: the design was changed so it could be assembled as quickly as possible; it was made off site; used new technology by bringing aluminium into a tunnel environment; it was a LEAN, production-focused solution; and it used parametric design and robotics.

Costain has gone on to apply learnings from the Crossrail walkway to other projects and is investing in the next-generation of tunnel fit-out. This includes the use of cast-in sockets to eliminate the need for drilling, and greater use of AI tools in design, such as CFD analytics. The company has also developed a trial robotics solution called ATRIS for lifting and fixing.

“Heavy tunnels are horrible environments to work in and quality is always an issue. We are sold on production thinking to solve these issues. We know it can save money and programme. However, things can and do go wrong. You still have to put the time and effort in and tackle the problem forensically or you won’t see the benefits.” 

Simon closed by confirming Costain’s commitment to production thinking. “We have a dedicated lead, we have developed tools and training, and we have embedded production thinking in our work-winning and delivery processes. Data is now our focus for 2024. It is where we need to go to really sell the benefits of this approach.”

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