The Clean Rivers Project is a massive $2.6 billion infrastructure program being undertaken in Washington, D.C., to prevent sewer overflows into local waterways, including the Anacostia and Potomac rivers. The problem stems from a third of the cities antiquated "combined sewer systems," which collect rainfall and sewage in the same pipes.
During heavy rainfalls, these systems become overwhelmed and sewage overflows into the local waterways. As a result, about three billion gallons of raw sewage is dumped into D.C.'s streams and rivers each year.
To mitigate the problem in Washington, D.C., the city launched the Clean Rivers Project – aka D.C.'s "Big Dig" – essentially an ambitious plan to build huge underground tunnels that will be able to store this sewage/rain water runoff until it can be safely transferred to a local wastewater treatment plant. The goal is to save the Anacostia and Potomac rivers from severe pollution – two rivers that are important waterways in D.C., and which eventually flow into the Chesapeake Bay.
The project is expected to be complete by 2025, and it is estimated that 96 percent to 98 percent of all sewage and storm water will be diverted and treated by this new system.
Currently, a 12,300-foot-long tunnel, called the Anacostia River Tunnel, is being built – it is the second of four tunnels. The three other tunnels include the Blue Plains Tunnel, the Northeast Boundary Tunnel and the Northeast Boundary Branch tunnels. The engineering team carving out the Anacostia River Tunnel is using a huge tunnel-boring machine (nicknamed "Lady Bird") more than 100 feet below the surface.
This enormous machine provides real-time data and includes geotechnical instruments that monitor the integrity of the infrastructure at or near the vicinity and surface of the tunneling. With a 26-foot diameter cutterhead and carbide drill bits, 443 feet long, this machine cuts through about 100 feet of "Potomac Clay" every day.
Changes to the project's conceptual design continue to be considered and debated. A "Green Infrastructure" modification has been proposed, which may allow for the shortening of one of the tunnels and perhaps eliminating the need for another tunnel altogether. This proposal essentially calls for replacing part or all of the tunnels with plant-filled drainage areas, cisterns, permeable alleys and rain gardens.
Environmental advocates, however, are highly skeptical of the changes and do not believe that this "green infrastructure" will be as effective as the tunnels.
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D.C. Water's website for the Clean Rivers Project can be found here:
An overview of the problem and the project can be found here:
A great video showing the tunneling process:
International Tunnel "web magazine" provides updates and specifics about the Clean River Project:
Discussions and descriptions regarding the proposed "green infrastructure:"