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Potomac River Tunnel

National Capital Regional Office » Potomac River Tunnel » Document List

The District of Columbia Water and Sewer Authority (DC Water) and the National Park Service (NPS) are seeking comments on an Environmental Assessment (EA) prepared for the Potomac River Tunnel project. The Potomac River Tunnel is a major component of DC Water's Combined Sewer System Long Term Control Plan, also known as the DC Clean Rivers Project. The project would substantially reduce untreated discharges from the combined sewer system to the Potomac River by increasing combined sewer overflow (CSO) storage and conveyance capacity. The project is needed to reduce CSOs that contribute to water quality impairment of the Potomac River and ultimately the Chesapeake Bay; and to comply with the 2005 Federal Consent Decree entered into by DC Water, the District of Columbia, the US Environmental Protection Agency, and the US Department of Justice, as amended January 2016. The proposed controls are estimated to reduce CSOs to the Potomac River by 93% by volume and reduce their frequency from approximately 74 events to 4 events in a year of average rainfall.

Portions of the project would be constructed on lands administered by the NPS. Therefore, the EA has been prepared to document compliance with the National Environmental Policy Act (NEPA), which is required for NPS issuance of construction permits for the project. The EA documents the analysis of environmental impacts from construction of a deep sewer tunnel and supporting infrastructure to provide control for CSO outfalls along the Potomac River in Washington, DC. Supporting infrastructure consists of near surface diversion facilities designed to divert flow from the existing combined sewer system to the tunnel during rain events. A ventilation control facility, emergency overflow structure, and drop, mining, and ventilation shafts would also be constructed. As described in the Federal Consent Decree, green infrastructure (GI) may be implemented in lieu of the tunnel to provide control for CSOs 027, 028, and 029.

The project was originally scoped as an Environmental Impact Statement (EIS) and a Notice of Intent was published in the Federal Register on July 2, 2014. However, since the Federal Register notice was published, DC Water and the NPS have identified opportunities to reduce potential project impacts through improvements to the tunnel design and the relocation of certain supporting tunnel infrastructure outside NPS lands away from significant park resources. The NPS has determined that based upon these design improvements and associated reduction of potential impacts an EA is the appropriate level of documentation for the proposed project.

Public comments will be accepted from October 25 to December 4, 2018. The EA can be found by clicking "Open for Comment" in the list of project links to the left. Click "Potomac River Tunnel EA" and then click "Potomac_River_Tunnel_EA_508_2018_10_25.pdf" to open the document. Click "Comment Now" under the project links to submit comments electronically. Comments may also be submitted in writing to:

ATTN: Potomac River Tunnel EA
DC Clean Rivers Project
Blue Plains Advanced Wastewater Treatment Plant
5000 Overlook Avenue, SW
Washington, DC 20032

A hard copy of the EA can be found at the following libraries:

Southwest Library, 900 Wesley Place SW
West End Library, 2301 L Street NW
Georgetown Library, 3260 R Street NW
Palisades Library, 4901 V Street NW

Comments must be provided electronically or postmarked by November 30, 2018 to receive consideration.

The public is invited to an open house on Wednesday, November 14, from 6:00 to 8:00 p.m. at West End Library (2301 L St NW, Washington, DC 20037). There, you will be able to discuss the project with NPS and DC Water staff, get your questions answered, and learn more about the project and the EA. Individuals requiring special assistance at the meeting please contact DC Clean Rivers Project Public Outreach at (202) 787-4717 or dccleanrivers@dcwater.com.