Potomac Interceptor Rehabilitation Project

The Potomac Interceptor Rehabilitation Project is a $625 million effort over 10 years to repair and strengthen one of the Washington region’s largest and most important sanitary sewer systems. The 54-mile pipeline carries about 60 million gallons of wastewater each day from parts of Northern Virginia and Maryland to DC Water’s Blue Plains Advanced Wastewater Treatment Plant for treatment. Built by the federal government more than 60 years ago, it was later transferred to DC Water to maintain and operate. The system includes 11 tunnel sections and two river crossings and serves Fairfax County, Loudoun County, the Town of Vienna, Herndon, Dulles Airport, and Montgomery County, Maryland.

The long-term rehabilitation project is part of DC Water's 10-year, $9.7 billion Capital Improvement Program that supports critical investments in safe, reliable drinking water and replacement of aging water and sewer lines. 

On January 19, 2026, a section of the Potomac Interceptor collapsed along Clara Barton Parkway in Cabin John, Maryland. Information about the incident, including ongoing water quality monitoring and the environmental rehabilitation efforts can be found here.