Video: Harriet the tunnel boring machine is now under Crenshaw Boulevard

A significant milestone recently occurred on the Crenshaw/LAX Line: Harriet, the tunnel boring machine [TBM], was lowered into the ground at the future Expo/Crenshaw Station.

In the above video, two large pieces of Harriet — the middle shield and cutterhead — are lowered into the site and then aligned with the front shield, another key piece of the TBM that had been previously lowered. The intricate process took more than an hour; the above footage was sped up to show the work in less than three minutes.

With the shield and cutterhead now in the station, assembly on the entire machine is underway. That should take about a month. It takes time because the TBM is a complex network of conveyer belts, wiring and cables that will be more than 400 feet long and will be able to safely remove 150,000 cubic yards of soil while digging the tunnels.

After Harriet is fully assembled, she will begin excavating and moving south under Crenshaw Boulevard from Exposition Boulevard toward Leimert Park. This stretch of track will include three underground stations: Expo/Crenshaw, Martin Luther King, Jr. and Leimert Park.

There’s also plenty of work happening along the entire 8.5-mile Crenshaw/LAX Line alignment. Check out this post for some fresh pics. And here’s the project home page.

13 replies

  1. This is interesting however here in San Francisco we got two TBMs and they bored twin tunnels north at the same time for our Centrel Sunday.

    • Hi Warren,

      It should take about 15 months.

      Contributor, The Source

  2. Is Harriet’s diameter sufficient for the entire two-track system that Metro requires? How wide is the diameter, anyway?

    • She’s 21-and-a-half feet in diameter. It’s sufficient for Metro’s two-track system because she’ll be excavating two twin tunnels, one for each track.

      Contributor, The Source

      • Do they send it south to LAX digging one tunnel, and then back north to Crenshaw to dig the other?

        • Hi Jamie,

          That’s right. The TBM will start by digging the southbound tunnel and then turn around at Leimert Park to dig the northbound tunnel.

          Contributor, The Source