The first of two Herrenknecht TBMs for DC Water’s Potomac River Tunnel has passed its Factory Acceptance Test.
TBM Mary passed the FAT at Herrenknecht’s factory in Schwanau, Germany and will now be disassembled and shipped to the US for DC Water’s Clean Rivers Project.
The 6.4m-diameter TBM, and her sister machine TBM Emily, will excavate an 8.9km tunnel. Mary and Emily will tunnel in opposite directions, cutting through bedrock and soil. Mary will be launched in autumn, working north 3.9km towards the tunnel’s endpoint near the entrance of Georgetown University. Emily will head south, tunnelling 5km to connect to the Anacostia River Tunnel system.
TBM Emily’s factory acceptance test is expected to take place in October. Herrenknecht has supplied TBMs for other tunnels on DC Water’s Clean Rivers Project.
“We are excited to mark this major milestone. These machines are truly a marvel of modern technology and must be custom built for the project,” said DC Water chief executive officer and general manager David L Gadis. “We look forward to Mary’s arrival. She and her sister TBM, Emily, will have their work cut out for them to dig the 8.9km tunnel.”
The two TBMs are named after Mary and Emily Edmonson, who made a daring attempt to escape from slavery on the Potomac River in 1848 and became heroes of the abolitionist movement.
The Potomac River Tunnel is designed to reduce the volume of sewer and stormwater released into the Potomac River by 93% in an average year of rainfall. That amounts to more than 600 million gallons of wastewater and stormwater which will be captured and sent to the Blue Plains Advanced Wastewater Treatment Facility for treatment. It is expected to be completed in 2030.
In October 2023 DC Water awarded the US$819m Potomac River Tunnel contract – the largest ever for the authority – to a joint venture of CBNA and Halmar.
