When it is completed, the airport terminal building will be a futuristic blend of open space, natural light and spectacular airfield views. The main building envelope is 384 metres long, 165 metres wide and 43 metres high. It is supported by 11 pairs of giant steel support arches, rising 39 metres from the ground. With two further sub-ground levels, overall floor space covers 300,000 square metres – or the equivalent of 50 full-size football pitches.

Whilst the project itself is futuristic in concept, traditional construction values are essential to its success. Quality of materials is, of course, an essential element and for the drainage systems beneath T5A, cast iron proved to be the material of choice.

AMEC were responsible for the design of the services to T5A and Laing O’Rourke, one of the main contractors involved in T5, is directly responsible for installation of the below-slab drainage systems on T5A substructures. A spokesman describes cast iron as “The Rolls Royce of materials”.

He says: “Everything we use has to be of top quality and cast iron is certainly that. Whilst it may be a traditional material, it has all of the modern qualities we need for a major and complex installation of this type. Joint couplings mean that the system can be very flexible and when you are working on multiple levels with a lot of different bends you don’t have to worry about dealing with varying access heights. From the installer’s point of view, cast iron systems are very straightforward and cost effective to fit. Timescales are always critical on a project of this scale, so being able to use a system that is fast and easy to fit has enormous advantages.”

While the flexibility of the system is a bonus at the installation stage, it is also the long-term qualities of cast iron that make it the ideal solution. As one Laing O’Rourke engineer says: “We know we have installed a system that will have a long life – we would expect over 50 years from this system with repair and maintenance being kept to a minimum.”

He continues: “The system we have used is manufactured to a high standard. It has an epoxy resin coating on the inside which offers chemical resistance and a zinc external coating makes it corrosion resistant, so it is well protected inside and out. All of the other qualities of cast iron also come into play: it is non-combustible and it has excellent sound deadening qualities. It is extremely robust, which is another important factor in an area of this type, which is a combination of massive steel and concrete structure. And finally, with respect to sustainability, cast iron is manufactured from recycled material and is ultimately fully recyclable.”