Piney Branch Tunnel
DC Water’s Piney Branch Tunnel
Piney Branch Tunnel overview
DC Water’s Clean Rivers Project is planning an underground storage tunnel that would prevent an estimated 4.2-million-gallon of untreated combined sewage with stormwater, known as combined sewer overflow (CSO) from flowing into Piney Branch during storm events when the capacity of the sewer system is exceeded. Once implemented, the project is estimated to reduce untreated CSO discharge into Piney Branch by an estimated 96 percent in a year of average rainfall.
The Piney Branch Tunnel Project is needed to 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 tunnel would be constructed in the general vicinity of combined sewer overflow (CSO) 049, a combined sewer outfall within Rock Creek Park. The purpose of the project is to reduce untreated discharges from the combined sewer system to Piney Branch, a perennial tributary that drains to Rock Creek, by increasing CSO storage and conveyance capacity. This will reduce the overflow frequency from 25 to one per year of average rainfall and reduce the overflow volume by approximately 96 percent.
The project includes construction of a diversion structure at the Piney Branch outfall, known as CSO 049, to redirect sewer flows to the storage tunnel and eventually convey the combined sewage to DC Water’s Blue Plains Advanced Wastewater Treatment Plant for treatment when the pipes and system can handle the volume. This project is needed to reduce CSOs to improve water quality in Piney Branch, Rock Creek, and ultimately the Potomac River and the Chesapeake Bay; and to comply with the terms of the Federal Consent Decree.
Schedule
| Environmental Assessment | 2024 |
| Procurement | 2024-2025 |
| Construction | 2025-2029 |
Environmental Assessment
DC Water and the National Park Service (NPS) have prepared an Environmental Assessment (EA) to comply with the National Environmental Policy Act (NEPA). The EA analyzes potential environmental impacts that would result from implementing the Project. As the coordinating agencies in the preparation of the EA, DC Water and NPS are working closely with multiple communities and stakeholders. In addition, DC Water is coordinating with multiple federal and local agencies and other organizations through the National Environmental Protection Act and the National Historic Preservation Act compliance procedures.
Public Participation
Public participation is vital to the NEPA review and planning process. DC Water and NPS are seeking comments on the EA prepared for the Piney Branch Tunnel project.
The EA will be available for a public review and comment period from October 15, 2024, to January 3, 2025. To review the EA please visit the project website at https://parkplanning.nps.gov/dcPineyBranch.
If you prefer to mail your comments, make sure they are postmarked by 11:59 pm EST on January 3, 2025, to receive consideration. Mail comments to the following address:
Superintendent
Rock Creek Park
RE: Piney Branch Sewer
3545 Williamsburg Lane NW
Washington, DC 20008
DC Water and the NPS value your input in shaping this project.
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