What’s happening below Crenshaw Boulevard?

The launch of the Crenshaw/LAX Line’s tunnel boring machine (TBM) Harriet is now weeks away. The first pieces of the massive tunneling machine were lowered into the excavation site at Expo/Crenshaw in late February.

Since then, work crews have been busy piecing together the machine’s trailing gear as well as the key components needed for Harriet’s initial launch into the soil. The photos above show the progress since we last saw her.

At launch Harriet will begin tunneling south under Crenshaw Boulevard from Exposition Boulevard toward Leimert Park. A fact sheet with more details about the TBM and its role in the project can be viewed here.

10 replies

  1. From the fact sheet:
    “Then it [the TBM] will turn around and dig all the way back to the beginning.”
    First time I’ve heard of a tunneling project that does this. Presumably the TBM will have to be disassembled back into smaller pieces and shuffled around in the Leimert Park station box. Metro, please cover this phase in good detail. TIA!

    • Hi Mike,

      The plan for the TBM has been revised since the fact sheet and sounds a little bit more like what you’re suggesting. Once the TBM breaks through at Leimert Park, the trailing gear for the TBM will be backed up to Expo/Crenshaw. The remaining TBM pieces will be lifted out of the Leimert Park station box and brought back to Expo/Crenshaw to start again on the second tunnel.

      Contributor, The Source

  2. I hope the ground is sturdy enough for the drilling and doesn’t create a big sink hole.

    • Speaking generally, as a TBM moves through the ground it installs concrete tube panels behind it, these are quite wrong enough to hold up the ground around it. Part of the trailing gear does just this.

      The infamous Hollywood sinkhole wasn’t caused by a failure of the TBM, the structural reinforcement or the ground itself; what happened was the contractor has accidentally started digging one of the tunnels a few inches off-track, and instead of fixing it properly they tried to modify the installed concrete panels in a way that weakened the structure.

  3. While they are digging, if they break anything (like a water main) are they going to fix it without cost to citizens?

  4. Wouldn’t it have been a lot easier and cheaper (and faster) to have built a monorail?
    Setting Simpsons references aside, China & Japan (both earthquake prone) have tons of them .

    • Japan has tons of rail transit in general. Subways, high-speed rail, commuter trains, streetcars …. monorails are just one part of a very transit-oriented country.

  5. All this tunneling is uncalled for. The Crenshaw Line should have been physically connected to the Expo Line so as a third route could be created. The entire system should be inter-connected so as alternate routes can be created and the ease of moving equipment for special events. Additionally the amount of time it takes to build a line is outrageous. What took six months in the early 1900’s to construct now takes several years. Is this backwards technology? Rails laid by hand. Supplies sometimes brought to the job site by horse and wagon. One only has to look to the major railroads to see how fast rail can be laid and put into service. It seems only prudent to build these lines as rapidly as possible in order reap the income projected as soon as possible. But instead we hear from the MTA that they would rather keep the contractors working as long as possible even if it increases the cost of construction.