Many of the case studies in our portfolio describe work done alongside partner UK Power Networks Services (UKPNS). UKPNS holds a long-term contract to provide and maintain the energy infrastructure for Heathrow, and recently celebrated 30 years as a partner for the airport. When works require civil engineering support, UKPNS frequently turns to WCS to fulfil that role. Here are just two of our recent collaborations.
Heathrow Substation 96
As part of their ongoing management of the power assets at Heathrow, an upgrade to an existing substation was to be designed and built in the form of a new modular substation. The only problem was that it was to occupy the same parcel of land as the existing which was to remain live until the changeover. WCS was called in to oversee the ground investigation and propose a conceptual design for the new substation. Once this was accepted, we moved to detailed design of the installation itself, plus associated infrastructure.
“Site constraints made this project especially challenging,” comments Matthew Smith, Associate at WCS. “Heathrow as a whole is challenging – space is so tight and there are so many services and other buried infrastructure that, really, you can’t put a hole in the ground anywhere without very careful preparation and analysis. But this project site was especially constrained, even for Heathrow.”
One difficulty was that cabling, feeder pillars and other existing infrastructure had to continue in operation, certainly until the new equipment was in place. At that point, some could be isolated and removed, but not before. To solve this problem, a containerised substation supported on an elevated steel frame was proposed as the design solution. This allowed clearance below for the in-situ infrastructure and maintenance access.
For WCS and Matthew, this is a familiar solution for such projects but, again, constraints made it unusually challenging. The new substation was to sit adjacent to, and indeed partly above, assets owned by Transport for London. “One of the stops on the Piccadilly Line is Heathrow Terminals 2 & 3, and the ticket hall is located right next to our site, below ground. Unsurprisingly, LUL wanted reassurance that our proposed solution would not negatively impact their structure.”
In addition to normal design documentation, WCS had to complete a Conceptual Design Statement for London Underground, outlining plans before works could be approved. “I think it helped that we have done many projects with London Underground too,” adds Matthew. “Our experience means we know what to provide in terms of the design and documentation that LUL need, and to keep the design phase of the project on programme.”
Once the conceptual design was accepted, detailed design could proceed. “Because of the restricted nature of the space, it was something of a chess game – you move a column to avoid an asset below, and you have to recalculate all of the load analysis, and see what effect that will have on the foundation, and whether that now fits,” continues Matthew.
WCS was asked to join this now completed project in 2019, with the substation up and running from 2022.
Heathrow Terminal 5 EV Coach Park
WCS were commissioned to carry out all civil engineering design for an innovative EV Coach Park at T5, including upgrading of the existing coach park to support an electric vehicle fleet. The existing surface here was heavily pitted, so resurfacing had to be carried out, with several new structures also required, including a welfare cabin for drivers and three substations. As usual, associated infrastructure had to be planned – ducts, troughs and foundations for additional elements such as feeder pillars and the actual chargers, as well as the substations.
Again, WCS was asked to oversee ground investigation, a service we were able to provide from our approved supply chain.
Fire safety added significant complications to the project. In the unlikely event of a vehicle battery fire, the risk exists of fire spreading across the fleet of parked busses.
In order to progress the design, the project partners commissioned independent fire safety consultants – again through the WCS supply chain – to prepare a formal report to assess the danger of fire spread and make recommendations for mitigation. Comments Matthew: “It was a vital early step in the process which informed the design development across disciplines and provided further reassurance to the client.”
WCS was fully involved in the fire safety discussion because there was civil engineering input required. The guidance followed at Heathrow necessitates that any area that could be flooded by the fire services arrival in the unlikely event of a vehicle fire also requires a subsequent drainage solution to prevent the potentially contaminated water runoff finding its way into Heathrow’s regular surface water system. In this case we designed a new underground isolation tank connected to a valve which can be manually triggered, to direct surface water to the isolation tank for safe collection at a later date. It was additionally decided that the appropriate method to prevent fire spread was to have approximately 4.5m high fire-proof barriers separating groups of buses when charging. The solution for this posed engineering challenges for WCS in the design, which uses a steel frame barrier structure rising off reinforced concrete foundations.
WCS started on this project in the summer of 2022, and expects to submit completed detailed design this summer (2023).