UPDATE: Piney Branch Parkway Reopens and Tunnel Work Proceeds

DC Water’s contractor has completed construction site preparation for the Piney Branch Tunnel project. On June 8, 2026, the relocated section of the Piney Branch Parkway was reopened between Arkansas Avenue NW and Beach Drive. With the Piney Branch Parkway relocated, the project can now proceed with shaft and tunnel work.

The above image shows the completed relocation of Piney Branch Parkway

Enhanced safety measures have also been put in place to protect drivers, cyclists and pedestrians. A new three-way stop has been added at Piney Branch Parkway and 17th Street. Rumble strips and jersey barriers with high-visibility reflective markings were installed as well to alert drivers of the new curve in the road.

The adjoining pedestrian and bike trail will be separated from the construction site by barriers and fencing. A raised crosswalk at the work zone entrance will also help pedestrians cross safely and there will be a defined path to guide cyclists through the area. Flaggers will also be on site when equipment or materials need to move across the road.

The trail along Piney Branch Parkway will be maintained for the duration of the project. Expect occasional short-duration closures. The roadway will be returned to the original alignment at the end of the project.

As part of the Clean Rivers Project, Piney Branch Tunnel will help keep combined stormwater and wastewater from being discharged into Piney Branch when the system exceeds capacity during heavy rains.  The tunnel, which begins at Park Road, will capture that overflow and send it DC Water’s Blue Plains Advanced Wastewater Treatment Plant. Once the tunnel is in service, it’s expected to cut overflow volume into Piney Branch by about 96% and the number of discharges from 25 times a year to only once, helping to protect public health and improve water quality in Piney Branch, Rock Creek, and the Potomac River.

Piney Branch Tunnel Project

DC Water’s Clean Rivers Project is constructing the Piney Branch Tunnel Project within Rock Creek Park in northwest Washington, DC.  The tunnel will capture and store a minimum of 4.2-million gallons of sewage combined with stormwater, known as combined sewer overflow (CSO), that will otherwise overflow into Piney Branch when the capacity of the existing combined sewer system is exceeded during storms. The United States Environmental Protection Agency (USEPA) currently lists Piney Branch as an impaired waterbody under the Clean Water Act.

The Piney Branch Tunnel Project will comply with the 2005 Federal Consent Decree entered into by DC Water, the District, the USEPA, and the US Department of Justice, as amended January 2016, and modified December 2020. The project is designed to improve water quality in Piney Branch, Rock Creek, and ultimately the Potomac River and Chesapeake Bay by reducing untreated discharges to the sewer system and increasing sewer overflow storage and conveyance capacity.

Currently, an estimated 40 million gallons of untreated combined sewer discharge overflows into Piney Branch in a year of average rainfall during heavy storm events. This harms local waterways and wildlife. Once completed, the Piney Branch Tunnel will capture and store most of this overflow during storms, reducing these overflows by 96% and limit the frequency of overflow events from 25 to one in a year of average rainfall.