The century-old sewage system that serves the District of Columbia in the United States is no longer able to manage the pressure placed upon it by urban growth. The system’s deficiencies are most apparent when it rains hard. It is small in scale and it quickly overflows in parts of the U.S. capital of Washington, sending stinking, untreated waters into the streets and the nearby waters of the Anacostia River and, ultimately the Potomac, which flows past the buildings of American power.

One of the solutions adopted by the district under its Clear Rivers Project has been to build a hydraulic tunnel called the Northwest Boundary Tunnel (NEBT) to enable it to manage better these overflows during rainstorms. The tunnel, built by Webuild, is 8.2 kilometres long and 30 metres deep. It will store excess water until the treatment plan can receive it.

As is the case for most underground work, residents do not see this invisible infrastructure being developed, in contrast to roads and railways, which are far more visible. “People cannot understand the importance of this work if we don't take them into the tunnel”, said Carlton Ray, Vice President of the Clean Rivers Project, during a Community Daily Tour. “It makes me so happy to know that this tunnel will save us from this problem”, said student Cathelin at the end of the tour. "And in 2025 we can go back to fishing and swimming in Anacostia”, added his friend William. Once the entire Clean Rivers Project is completed, the system will be able to reduce by 96% the amount of untreated wastewater that flows in the nearby water bodies, improving the quality of life of some five million residents.