Today, DC Water celebrated a major milestone in the Potomac River Tunnel Project with the ceremonial blessing of Mary, the tunnel boring machine (TBM) that will dig the northern leg of the tunnel. The event, at West Potomac Park, marked the official start of tunneling for one of the final and most ambitious phases of DC Water’s Clean Rivers Program.

Mayor Muriel Bowser led the ceremonial blessing with a bottle of DC tap water, symbolizing the District’s commitment to cleaner waterways and marking the beginning of Mary’s historic journey beneath the Potomac River. She was joined by DC Water CEO and General Manager David L. Gadis, DC Water Board Chair Dr. Unique N. Morris-Hughes, and other District leaders, to celebrate the beginning of this transformative infrastructure project.

“The DC Clean Rivers Program plays such an important role in ensuring that we are the safe, clean and beautiful city that we are today,” said Mayor Muriel Bowser. “Whenever you make this type of investment in world-class infrastructure, that’s an investment in our collective future, it’s an investment in safe neighborhoods and clean, swimmable waterways, and it’s an investment in our position as a beautiful waterfront city."

Mary is named after abolitionist Mary Edmonson, who—along with her sister Emily—attempted a daring escape from slavery via the Potomac River in 1848. Her sister TBM, Emily, is scheduled to arrive later this year from Germany to dig the southern leg of the tunnel. Together, they will construct the 5.5-mile Potomac River Tunnel, designed to intercept nearly one billion gallons of combined sewage and stormwater overflows from entering the Potomac River in an average year of rainfall.

“Today we celebrate not just a machine, but a movement,” said David L. Gadis. “The Clean Rivers Program has been a game-changer for our city. We’ve watched the Anacostia River come back to life, and now, with Mary leading the way, we’re turning our focus to the Potomac. This tunnel is one of the final pieces of a legacy that will leave our rivers cleaner, our communities healthier, and our future brighter.”

The tradition of blessing TBMs before they begin tunneling is rooted in centuries-old mining customs. Saint Barbara is revered for her protection against the dangers of underground work, and DC Water has embraced this tradition in past projects, including the Anacostia River Tunnel, as a way to honor the workers and the significance of the infrastructure being built.

Following the ceremony, attendees toured the launch site and viewed the 100-foot-deep drop shaft where Mary will begin her excavation. This shaft is a critical part of the tunnel system that will carry stormwater and sewage to DC Water’s Blue Plains Advanced Wastewater Treatment Plant.

The Potomac River Tunnel Project is a key component of DC Water’s Clean Rivers Program to reduce combined sewer overflows and improve water quality across the District. Once completed in 2030, the tunnel will reduce overflow events from 74 to just four in an average year of rain and cutting overflow volume by 93%.

The blessing of Mary marks a turning point in the Clean Rivers Program — a moment that blends engineering excellence with environmental stewardship. As she begins her journey underground, Mary carries with her the hopes of a cleaner, healthier Potomac River and a legacy of progress for the District.

For more information about the Clean Rivers Program and the Potomac River Tunnel Project, visit dcwater.com/prt.