The Washington DC Metropolitan Area Backup Water Supply Feasibility Study is a comprehensive planning effort led by the U.S. Army Corps of Engineers (USACE), Baltimore District. The primary purpose of this study is to evaluate and identify a secondary water source and additional raw water supply for the Washington D.C. Metropolitan Area (WMA). This critical initiative ensures that regional water supply utilities can deliver enough water to meet demand during emergencies when raw water cannot be safely withdrawn from the Potomac River due to contamination or during severe drought.

The study is formally authorized under the Water Resources Development Act (WRDA) of 2022, Public Law 117-263, Division H, Section 8201(a)(14), dated December 23, 2022. This federal legislation directs USACE to conduct this feasibility study.

The Metropolitan Washington Council of Governments (MWCOG) serves as the non-federal sponsor for this cooperative effort. Funded initially by a $500,000 appropriation under the Energy and Water Bill of 2024, the study operates under a Feasibility Cost Sharing Agreement (FCSA) signed on September 30, 2024. The study is currently funded with 90% federal and 10% non-federal cost-share, per WRDA 2024.

The study area encompasses the entire WMA, spanning the District of Columbia, northern Virginia, and Maryland. Within this region, the study focuses specifically on local jurisdictions and water utility service areas that depend directly on the Potomac River as their primary source of raw water.

The regional water supply infrastructure serves over 4.6 million residents. In addition, the WMA employs more than 3 million people. The National Capital Region is also home to the federal government and hundreds of government defense facilities, including major military bases, the Pentagon, the U.S. Capitol, and the White House. The Washington Aqueduct—a division of the USACE Baltimore District—is the nation’s only federally owned and operated public water supply agency.

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Study Objectives include:

1. Reduce the vulnerability of the WMA’s raw water supply during times when the Potomac River is contaminated, and
2. Mitigate water supply dependence on the Potomac River in the event of drought.

There is one Planning Constraint:

1. Maintain the quality of the water supply to meet regulatory standards.

In identifying viable solutions, USACE evaluated many strategies, including new reservoir storage, existing reservoir modification, direct or indirect wastewater reuse, desalination, diversions from other regional basins, and enhanced interconnections, tunnels, or intakes.