The second TBM for the Potomac River Tunnel has been lowered into the launch shaft.
The CBNA/Halmar International joint venture has lowered TBM Emily into the 30.5m-deep shaft at West Potomac Park.
The TBM, which is designed to tackle the softer ground conditions along the southern section of the alignment, is now being assembled and tested ahead of the start of tunnelling operations.
The new machine is due start tunnelling towards Joint Base Anacostia-Bolling in December. It will join TBM Mary, which was launched in April to excavate the 3.87km northern section through hard bedrock towards Georgetown University.
The two 6.4m-diameter Herrenknecht TBMs will operate simultaneously, boring in opposite directions.
The 8.9km-long Potomac River Tunnel project is part of DC Water’s Clean Rivers Program, which aims to capture and convey excess flows from the sewer system, and improve water quality in the Potomac River and Chesapeake Bay.
