By rosebell
As the first of two Herrenknecht TBMs for DC Water’s Potomac River Tunnel, TBM Mary has passed its Factory Acceptance Test at Herrenknecht’s factory in Schwanau, Germany and currently is going to be disassembled and shipped to the US for DC Water’s Clean Rivers Project.
While excavation of an 8.9km tunnel is up to this 6.4m-diameter TBM, and her sister machine TBM Emily, they will tunnel in opposite directions, cutting through bedrock and soil. The date of commissioning Mary will be the autumn, working north 3.9km towards the tunnel’s endpoint near the entrance of Georgetown University, whereas Emily is due to head south, tunneling 5km to link to the Anacostia River Tunnel system.
The scheduled date for implementing TBM Emily’s factory acceptance is 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. 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,” said DC Water chief executive officer and general manager David L Gadis.
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.
With the aim of reducing the volume of sewer and stormwater released into the Potomac River by 93% in an average year of rainfall, the Potomac River Tunnel is designed, while that amounts to over than 600 million gallons of wastewater and stormwater which is going to be captured and sent to the Blue Plains Advanced Wastewater Treatment Facility for treatment. It is expected to be completed in 2030.
As the largest ever for the authority, the US$819m Potomac River Tunnel contract was awarded to a joint venture of CBNA and Halmar in October 2023 by DC Water.
