Emily, the Potomac River Tunnel Project's final TBM, has successfully completed its factory acceptance testing. The machine, built by Herrenknecht, will excavate the southern leg of the Potomac River tunnel — a critical step toward reducing sewer overflows and protecting local waterways.

Emily will join sister TBM Mary, which is scheduled to begin digging the northern leg of the tunnel in early 2026. The two TBMs are named after Emily and Mary Edmonson - courageous abolitionists from the DC area. 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, Emily will be disassembled for her journey to Washington, DC. The machine will be reassembled at the West Potomac Park site in spring 2026.

Click here and us/109 for tunnelbuilder archive. Visit https://www.dcwater.com/. 43/25.