First turn of cutterhead signals the start of excavation for the Potomac River Tunnel Project

In a defining moment for one of the District’s largest infrastructure investments, DC Water has marked its next major milestone in the Potomac River Tunnel Project. The first tunnel boring machine, Mary, has launched her northbound journey breaking through the soil to signal the start of excavation.

With the first turn of Mary’s drill-like cutterhead underground, the machine pushed forward to begin tunneling, representing the transition from years of planning and preparation to active tunnel construction on the $819 million project.

• DC Water has completed soil removal, utilizing excavators and manual digging, to expose the clay lining for the C & O Canal between locks 13 and 14. This is the final step in the clean-up process ...

Work is progressing on the clean-up for the C & O Canal which was used as a bypass while the Potomac Interceptor was repaired. Workers are focused on removing sludge between locks 11 and 12. Soil removal is also nearly complete between locks 12 and 14, reaching the canal's clay liner. Workers are now manually removing additional materials in some areas.