USA: Pure water in the Capital
ANACOSTIA RIVER TUNNEL, USA
Washington was immediately thought of as a modern and efficient city when it was first designed by French architect and urban planning expert Pierre Charles l'Enfant. Since 2010, it is at the heart of a modernization plan, one of the most cutting-edge and complex projects dedicated to managing and containing river water: i.e. the DC Waters Clean River, a 20 year project that cost $2.6 billion to reduce pollution and overflooding of the Potomac River and its affluents: the Rock Creek and the Anacostia.
A large scale operation to control the discharges and capture and purify water before it has the chance to reach the existing rivers, therefore safeguarding population, the ecosystem and wild fauna.
An important piece of the programme - whose pivoting point is the Northeast Boundary Tunnel - is the Anacostia River Tunnel. 3.8 km long, it is largely developed under the river's waters, with 6 water catchment wells (9 to 22 metres in diameter and 30 metres deep), 3 connecting tunnels (1.4 and 3 metres in diameter), and various concrete works including 5 aeration and gas control chambers; all built and put into operation in 2013-18.
An engineering challenge that used highly innovative technologies, including next-generation gaskets and fiber-reinforced segments, in their first use in the United States. Geologists, geotechnical engineers, divers, and hyperbaric medicine specialists were involved in the construction of the Anacostia River Tunnel - a truly complex and technologically advanced work that won awards such as Sustainability Initiative of the Year in 2017 and ENR Global Best Project Award in 2018.
And do you know why? Because thanks to the Anacostia River Tunnel, the danger of flooding has been reduced by 86 percent, while the volume of untreated rainwater and wastewater has dropped by 98 percent.
THE WORK AND THE TECNIQUE
KM TUNNEL
SHAFTS
TUNNELS
DC WASA - District of Columbia Water and Sewer Authority
Joint venture Salini Impregilo (now Webuild Group), SA Healy and Parsons Group.
Sustainability Initiative of the Year award (2017) given by the International Tunnelling and Underground Space Association (ITA-AITES).
The Award of Merit in the water/wastewater sector (2018) awarded by ENR Global Best Project Award
CULTURAL INSIGHTS
The last double mile
The District of Columbia's main water authority, DC Water, disclosed that the Anacostia River Tunnel prevented more than 17 billion gallons of material from the metropolitan area's sewer system (where more than 6.30 million people live) and 900 tons of solid waste from flowing into the river in the tunnel's first year of operation.
This system prevented in a marshy area with high average rainfall, shallow groundwater and historically prone to devastating floods this system has essentially prevented 90% of waste and sewage from flowing into the freshwaters of the Anacostia River, exceeding even the most optimistic expectations, which had been based on a year of average rainfall.
Thanks to black and white-water segregation and stormwater capture over the past decade, the water quality of the Anacostia has improved considerably until it was awarded the first positive grade in the State of the River Report Card in 2018.
Danger of floods
Volume of untreated rain water and waste water
Waste and liquid sewage in the Anacostia River
You could also be interested in
Discover other works
