Final TBM prepares for shipment from Germany to DC, marking a major milestone in the Clean Rivers Program

DC Water has reached a major milestone in the Potomac River Tunnel Project with the successful completion of factory acceptance testing for its final tunnel boring machine (TBM), Emily. This test confirms that Emily is ready to begin excavating the southern leg of the Potomac River Tunnel — a critical step toward reducing sewer overflows and protecting local waterways.

Led by Chief Executive Officer and General Manager David L. Gadis, DC Water’s team traveled to the German factory where Emily was built to ceremonially activate the cutterhead — a massive drill-like component that will carve the tunnel beneath the river.

“Seeing Emily in action was a powerful moment for our team and underscores the scale and impact of what we’re building,” said Gadis. “It’s one thing to plan and design a tunnel boring machine, but watching it take shape reminds us why we do this work — to build a cleaner, healthier future for the District.”

During the factory acceptance test, engineers from Herrenknecht, the TBM manufacturer, ran Emily through a series of operational checks. These included spinning the cutterhead, cycling the thrust rams, and activating the conveyor system — all designed to simulate real tunneling conditions and confirm the machine’s readiness.

Emily will join sister TBM Mary, which is scheduled to begin digging the northern leg of the tunnel in early 2026. Named after Emily and Mary Edmonson — courageous abolitionists from the DC area — the machines reflect DC Water’s commitment to honoring local history while building a cleaner future. Emily is engineered for softer soils, while Mary is designed to cut through hard rock, accommodating the varied geology along the tunnel’s path.

With testing complete, the next chapter begins as Emily prepares for her journey to Washington, DC. The machine will be disassembled for transport and reassembled at the West Potomac Park site in spring 2026. That’s when Emily begins her underground mission beneath the river — ready to dig.

The Potomac River Tunnel is part of DC Water’s Clean Rivers Program, a long-term initiative to reduce pollution in the Potomac River and Chesapeake Bay. Currently, about 650 million gallons of untreated sewer overflow enter the river each year. Once completed, the 5.5-mile tunnel system will reduce overflow volume by 93% and cut the number of overflow events from 74 to just four in a typical year.

Learn more about how DC Water and the Potomac River Tunnel Project are helping create a cleaner, better environment, healthier communities, and support the river’s diverse ecosystem at dcwater.com/prt.