The UK Government has given its official approval for a £33 billion plan to expand London’s primary airport, Heathrow. The project includes the construction of a new third runway measuring 3.5km. However, this plan will require London’s busy M25 gyratory motorway to be relocated 150m to the West, with a section running through a tunnel.
Construction of the runway itself could cost £21 billion. The design of the runway has yet to be decided but it seems likely that this will feature concrete base layers with asphalt layers on top, a structure that allows longevity while ensuring a smooth surface and retaining skid resistance in Britain’s sometimes inclement weather. The financing for the project will come from private sources.
An alternative plan for a slightly shorter runway of 2.7km that would not have required the motorway to be relocated was rejected. Although this would have been significantly cheaper at £23 billion, it was not considered as providing sufficient capacity for larger aircraft for the future.
Moving the M25 will be no small engineering feat and the new tunnel will have to be sufficiently wide to cope with the heavy traffic volumes that the M25 handles at present, as well as providing the capacity for anticipated traffic growth. The M25 is one of the busiest motorways in Europe, handling around 220,000 vehicles/day and having seen peak traffic levels well over 262,000 vehicles/day. The section passing Heathrow Airport also features very high traffic loads, so the new twin tunnels will have to be wide enough to provide sufficient space for the necessary lanes. This portion of the project is expected to cost £1.7 billion, with a cut and cover type tunnel being the most likely option. Whether this will also have a stipulation saying that no diesel machines will be allowed onsite and that electric or hydrogen-fuelled equipment will be required instead, as with the Lower Thames Crossing project now gearing up, remains to be seen.
There will also be major upgrades to other facilities across the airport to deliver the necessary capacity. The expansion project will boost the airport’s capacity to 756,000 flights/year and 150 million passengers/year. The project is to be fast-tracked through the permissions process, allowing construction to start in 2029.
The project to build the third runway is not without controversy however. The option selected will require the demolition of several homes next to the airport and there are environmental concerns over the work needed to the area. A number of rivers and several existing roads will have to be diverted, while the airport boundary will be expanded to the North (where the homes will be demolished). There are also environmental and safety concerns over the increased numbers of flights passing over London, an estimated jump of 760 flights/day overflying the city.
