Major Milestone in Sewer Line Repair Near Great Falls

DC Water crews pumped out the last of the wastewater from the bypass system, then carefully lifted the two-ton steel gate that had sealed off the newly rehabilitated section of the Potomac Interceptor Sewer Line. With the gate raised, wastewater from Virginia surged into the new 54-inch sanitary sewer line, joining flow from Maryland and connecting both to the upgraded infrastructure for the first time.

This final connection near Great Falls signals the new pipe section is now fully operational— renewing a critical part of the region’s sewer system. This achievement represents a significant step in completing this complex and critical infrastructure project, which began in 2022 and faced a setback last year when a part of the original pipe collapsed during construction.

The Potomac Interceptor is a massive sanitary sewer system capable of carrying nearly 100 million gallons of wastewater daily from communities in Virginia and Maryland to DC Water’s Blue Plains Advanced Wastewater Treatment Plant. Rehabilitating key sections of the 54-mile-long sewer line is a high priority project, within DC Water’s Capital Improvement Program to upgrade aging infrastructure.

The newly rehabilitated section of the Potomac Interceptor also incorporated a Vortex Flow Insert (VFI) into the design to improve air quality and reduce long-term maintenance costs. The specialized device spins wastewater in a spiral design, aerating the wastewater to help reduce odor and corrosion.

While the final connection has been made, the project will continue through the end of the year to complete some remaining work, including:

• Connect the new pipe to the existing odor control facility
• Fill and seal the old pipe with concrete
• Install manhole risers and a cover over the vortex
• Backfill the excavation site
• Restore the Potomac Heritage Trail and surrounding natural environment

*Revegetation is not expected until spring 2026, once weather conditions are more favorable.

The upgraded infrastructure reduces the risk of future failures, minimizes odors, and improves environmental conditions near residential areas and public spaces. By modernizing this critical pipeline, DC Water is also helping to safeguard public health, support regional growth, and ensure that wastewater is safely and efficiently transported for treatment. These improvements will also deliver long-term cost savings by improving reliability and reducing the need for emergency repairs and frequent maintenance.

DC Water continues to work closely with local partners, including NOVA Parks and Fairfax County, to ensure transparency and community engagement as this project moves toward completion.

For more information and project updates visit the Potomac Interceptor Project page at dcwater.com/potomacinterceptor.