The first episode follows the creation of the first stretch of the super sewer in east London. Lead engineer Emmanuel Costes has to build a massive 80-metre deep shaft that connects to the super sewer 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. The programme follows Steve Perry and his team at the treatment works in Beckton as they attempt to install the biggest pumps ever used in Britain to deal with sewage. The pumps are critical - with so much more sewage due to head to Beckton via the new super sewer, each one has to be capable of pumping three cubic metres of sewage per second. If they aren't installed correctly, millions of tonnes of the capital's waste will be stuck underground.