Potomac River Tunnel project
Reducing combined sewer overflows to protect the Potomac River
DC Water Authority
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Washington, D.C., USA
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2024–2030
The largest-ever awarded contract by the DC Water Authority, at $819 million.
Expected to curtail combined sewer overflows to the Potomac River by 93% during average rainfall years.
Part of the $3.29-billion DC Clean Rivers initiative to improve water quality in the region.
Challenges
- In a year of average rainfall, over 70 combined sewer overflow (CSO) events discharge approximately 654 million gallons of CSO in the Potomac River.
- As part of the DC Clean Rivers project, the Potomac River Tunnel (PRT) project aims to construct a 5.5-mile-long tunnel to control these CSO events and improve the river’s overall water quality.
- The PRT project is a critical piece of the broader Clean Rivers project—a $3.29 billion initiative to improve water quality in the Anacostia and Potomac Rivers, and Rock Creek, while strengthening the sewer system’s capacity.
Solutions
- Secured a design-build contract for the construction of the Potomac River Tunnel alongside CBNA, Halmar, and COWI.
- Responsible for overall design management and the detailed design of underground works, including support of exaction and concrete structures.
- The project requires precise engineering and the use of innovative construction techniques to manage unique surface and subsurface challenges.
- Construction will navigate various ground conditions, ranging from soft ground to rock, using advanced tunnel boring machines.
Highlights
- The PRT project represents the largest-ever awarded contract by the DC Water Authority, at $819 million.
- The 18-foot-diameter tunnel will serve as a crucial mechanism to control CSOs and will extend to Hain’s Point, ultimately connecting to the Anacostia River Tunnel.
- By 2030, the tunnel is expected to curtail CSOs to the Potomac River by 93% during average rainfall years.
"We always want to work with the best in the industry. We chose a partner that would be together with us from feasibility studies into construction to prove the process design. The importance of this was to have a consistent partner that we can rely on. Thats why we chose a tier 1 partner like Hatch."
Project numbers
$819 million budget
5.5-mile tunnel length
18-foot diameter
93% reduction in CSOs
2030, expected completion