When London’s current water treatment system was designed 150 years ago, the city had four million inhabitants.

The population has more than doubled since then. The 1,800 kilometers of brick tunnels from the Victorian era can’t hold all of the city’s sewage. When it rains, the system becomes overloaded. Then, the excess water runs into the river. Every year, 55 million tons of raw water end up in the Thames.

The Thames Tideway Tunnel, built in part by Ferrovial Construction, will reduce this figure by 90%. When finished, the tunnel will run under the river for 25 kilometers, connecting the old sewage system’s locks and outlets and collecting network overflows. From there, wastewater will be directed to the Beckton treatment plant south of London.

The works of Ferrovial Construction

Our task consists of excavating the 12.7-kilometer central tunnel from Fulham to Bermondsey. Two tunnel boring machines (TBMs) measuring 8.8 meters in diameter will be used. They operate under high pressure and at depths of up to 60 meters under the river bed. The project also entails building eight wells and pumping stations, as well as handling the earth extracted.

When finished, this large drain under the Thames will use gravity to funnel excess sewage away from the city to where it can be treated.