DC Water’s fourth tunnel boring machine (TBM) is chewing its way under Tingey Street today to create a tunnel to support healthier waters. This work is part of the Tingey Street Diversion Sewer. The 8-foot-diameter TBM was launched from a shaft just east of Nationals Park and is remote-controlled, set on a specified course connecting from 2nd to just beyond 5th Street, SE, running under Tingey Street. The tunnel is part of a massive $2.6 billion environmental program, called the DC Clean Rivers Project, to improve the health of local waterways.

As in many older cities, about one-third of the District has a combined sewer system, meaning that both runoff and sewage are conveyed in the same pipe system. Combined sewer overflows, CSOs, occur during intense rains when the volume exceeds the capacity of the pipes, and some of it must overflow to the nearest water body rather than backing up in homes and streets. Modern engineering avoids this problem with separate pipes for sewage and stormwater. Since the early 1900’s, only separate sewer systems have been installed in the District. DC Water’s plan to significantly reduce CSOs to the Anacostia River is to build massive underground tunnels that will store the combined sewage and runoff during intense rains and then slowly release it when the system has the capacity to treat it.

DC Water General Manager George S. Hawkins, commented, “Evidence of the work for the Clean Rivers Project can be seen across the District, and this tunnel is another step towards our ultimate goal of healthier waterways. When the projects are complete, DC Water will reduce CSOs to the Anacostia by 98 percent and to all of our waterways by 96 percent.”

The Tingey Street tunnel is about 1,200 ft long, has a six-foot-diameter concrete lining and will be able to convey more than 50 million gallons per day of combined sewage to Blue Plains for treatment. It is typical to name tunnel boring machines and this one was ceremoniously named “Go Yard” before being lowered into the launch shaft. It is expected to accomplish its mission and “break through” this week. A larger TBM, the 26-foot-diameter Lady Bird, is currently under the Potomac River, tunneling north for a total of more than 20,000 linear feet. There is also a smaller TBM under M Street, SE, and last year’s tunneling at the 11th Street Bridge on the south side of the Anacostia River was performed by another small TBM.

For more information on the DC Clean Rivers Project, please visit www.dcwater.com/cleanrivers.