The Five Billion Pound Super Sewer
London’s Victorian sewer network is at bursting point. Its tunnels are regularly pushed past their limit, and each week the equivalent of 300 Olympic swimming pools full of raw sewage is released into the Thames, totalling 39 million tonnes every year. Now a huge engineering project is underway to massively expand the capital’s capacity to deal with its own waste.
The first episode follows the creation of the first stretch of the supersewer in east London. Lead engineer Emmanuel Costes has to build a massive 80-metre deep shaft that connects to the supersewer and make it watertight using a specialist technique called ‘slipform’. It is a risky approach as it involves pouring concrete constantly for 15 days – and delays could spell financial disaster.
In this second episode, construction begins in the heart of London. Two key connection shafts along the Thames are to be dug to enable the super-sewer to be built. In Battersea, a challenging construction technique called ‘diaphragm-walling’ is employed to build a massive 90-metre-deep shaft. But these are the deepest tunnels ever dug in London, and with challenging rocks that haven’t been disturbed for 52 million years, the digger struggles to cut through the ground.
In this third and final episode of the series, tunnelling in central London finally begins. To complete the 16-mile main section of the super sewer, four bespoke tunnelling machines have been designed and work is underway to prepare for their launch. In Battersea, one of the strategically most important sites on the project, the team must assemble the 15m tunnel boring machines on site.