Something big is happening underground, as DC Water marks a major step forward for the Potomac River Tunnel Project. Today, crews successfully lowered the massive cutterhead for the tunnel boring machine (TBM) Mary. The 21-foot diameter cutterhead acts as a giant drill, to cut through rock and soil as Mary excavates the northern section of tunnel.

Beginning the week of January 12, 2026, DC Water will begin the next phase of construction for the Potomac River Tunnel Project at the Georgetown University entrance site along the Canal Road NW.

Learn more about winter replacements and protecting pipes from the cold

When temperatures plunge and the ground freezes, replacing lead service lines becomes more challenging—but DC Water doesn’t stop. Our Lead Free DC (LFDC) crews adapt. To learn more DC Water is hosting a virtual community meeting 6 - 7 p.m., Jan 28.