Designing the deepest point on London’s Elizabeth line

We developed the designs for the civil, structural, architectural, mechanical and electrical elements, and provided construction planning, passenger and transport modelling, and rail safety assurance services. During the design phase, we had a 120-strong team working on this one station.

Space at Liverpool Street was limited. The station is in a busy area and had to be built with minimal disruption to the daily lives of people and local businesses.

David Eastland, who was lead MEP design director on the station, responsible for developing the mechanical, electrical, public health, fire, acoustics, and escalator and lift engineering systems, says the physical constraints made the station one of the trickiest to design and build. They included expensive real estate, Victorian sewers, existing Tube lines and the Post Office railway. A 16th century burial ground was an additional complication. Archaeologists uncovered 4000 human skeletons between 2m and 4m below street level that had to be exhumed and relocated.

“We had to create a great space underground for travellers, but also provide for all the ‘back of house’ systems and equipment,” says David, “all while being sensitive to our neighbours and the surface environment.”

At Broadgate, between the two ticket halls, some 22 telecommunications ducts, 18 high-voltage power cables and two water mains had to be diverted before work could begin. However, they could not be relocated to nearby streets because of the shallow depth of London Underground tunnels. So we designed a ‘corridor’, a ventilated cut and cover structure, to house this tangle of utilities. Co-ordinating the two-year diversion project involved careful negotiation and planning to ensure there was no disruption to services. The benefit for utility companies is that maintenance work can be carried out, or additional services installed, without excavating the road and disrupting traffic.

At the Moorgate ticket hall, we had to align escalator shafts to avoid a huge egg-shaped brick sewer tunnel designed by the 19th century pioneer of municipal sanitation, Joseph Bazalgette (see the story about the Moorgate shaft).

Existing structures restricted the ceiling height at Moorgate. With principal architect WilkinsonEyre “we worked hard to co-ordinate the aesthetics and the services requirement,” says principal engineer Stuart Hill, who designed the hall’s lighting system and electrical services. “An integrated services spine maximised ceiling height. And the exposed fibre-reinforced precast concrete cladding is white, and glows with indirect lighting, giving the feeling of space.”

The Liverpool Street ticket hall is connected to the platforms by inclined lifts, which glide up and down alongside the escalators. Conventional vertical lifts would not fit in the space available, requiring demolition. Inclined lifts overcame that challenge.

The escalators were designed as composite structures formed by a primary lining installed using steel fibre reinforced sprayed concrete, followed by either a sprayed or sheet waterproofing system, then a secondary lining. Due to access limitations, the pilot tunnels for the escalators were excavated up-hill.

Inbuilt resilience

Designers must plan for the unexpected even if futuristic forecasts seem science fiction. David notes that the initial design for MEP systems at Liverpool Street were being developed at the same time in 2007 as Apple launched its first iPhone. “No-one would have envisaged that within 10 years most people on the move would be streaming all kinds of data to handheld devices. Contactless payment through a phone was unheard of,” says David.  Similarly, lighting in 2007 was mostly fluorescent lights, but the station was designed to be able to install light-emitting diode (LED) systems, which were then still in their infancy and have since become the default selection for all buildings wanting to meet BREEAM and CEEQUAL sustainability standards.

“Resilience is crucial and the design for Liverpool Street has to ensure there will be no overload whatever new systems are installed in the future,” says David. That’s about delivering end-to-end connectivity for today, and thinking about future expectations, such as the space, access and cabling routes for what might come. It’s not just about accommodating new technology though. The design of Liverpool Street and other stations considered future impacts of climate change, particularly flooding. The infrastructure is protected from potential flooding in 2100 or beyond, even in the event of a possible failure of the Thames flood defences.