The tunnel boring machine (TBM) for the Regional Connector resurfaced Friday, Dec. 8, at the future Grand Avenue Arts/Bunker Hill Station. The TBM began digging the second tunnel on the project in late September and traveled approximately 4,400 ft from Little Tokyo to reach the deepest station on the alignment.
Crews from Regional Connector Constructors (Skanska/Traylor JV) used what they learned from building the first tunnel to dramatically increase their rate of production on this tunnel. Typically, TBMs will travel 60 to 100 ft per day when working in similar soil conditions. The TBM, however, traveled a remarkable 190 ft in a single day — the TBM’s personal best — and averaged more than 400 ft per week. Crews erected 739 precast concrete rings to build the tunnel so far.
The Herrenknecht TBM will now be walked through the station and re-launched at the west end by the end of the month. To complete the second tunnel, the TBM will need to dig through another 1,370 ft of soil to reach the extraction point at the intersection of 4th and Flower streets in early January.
The $1.75 billion Regional Connector Transit Project is a 1.9-mile underground light-rail extension that will connect the Blue, Expo, and Gold Lines in downtown Los Angeles and will include three new stations. The project will reduce the need to transfer on Metro’s light rail system and make trips to and through DTLA faster and more convenient. The project is scheduled to be completed in late 2021.
A video of the hole-through is available here.