DC Water lowers massive cutterhead for Potomac River Tunnel Project

DC Water lowers massive cutterhead

DC Water took a major step Tuesday in the Potomac River Tunnel Project, lowering the cutterhead for ‘Mary,’ the tunnel boring machine that will dig the northern section of the new tunnel.

WASHINGTON - DC Water took a major step Tuesday in the Potomac River Tunnel Project, lowering the cutterhead for ‘Mary,’ the tunnel boring machine that will dig the northern section of the new tunnel.

The 21‑foot‑wide cutterhead acts like a giant drill, carving through rock and soil as the machine moves forward underground.

Because ‘Mary’ will stretch more than 700 feet once fully assembled, crews must lower and assemble each component one after the other.

Once the front sections are in place, ‘Mary’ will begin her 2.4‑mile journey from West Potomac Park to the Georgetown University area. ‘Emily,’ a second tunnel boring machine, will dig 3.1 miles south to Joint Base Anacostia‑Bolling, where it will connect with the Anacostia River Tunnel.

The Potomac River Tunnel is part of DC Water’s Clean Rivers Project, designed to capture stormwater and sewage during heavy rain, prevent overflows into the Potomac River and improve water quality.