L.A. Metro completes D-Line subway extension tunnel

California Construction News staff writer

Tunneling has been completed for the Metro Los Angeles D Line (Purple) Extension — a major milestone.

The planned expansion under the Wilshire corridor has added nine miles to the LA Metro D line connecting downtown LA with West LA over the last five years.

Contractors used two tunnel boring machines (TBM) to excavate 40 to 60 feet of tunnel each day. Metro will now continue to work with Skanska-Traylor-Shea and Tutor-Perini/O&G to complete seven new underground stations along the route.

The 400-foot-long, 21-foot-diameter machines used closed-face, pressurized TBM technology that minimizes ground settlement during excavation. They also lined the tunnel with precast concrete segments that were bolted together to form secure rings that are water- and gas-tight.

“During the five years of tunnelling, Metro overcame several technical challenges such as gassy ground, tar sands and engineering feats that Metro has undertaken,” said Lindsey Horvath, chair of the LA County Board of Supervisors and Metro Board Member. “The complexity is matched by the immense value the project will bring to Los Angeles when it opens and carries 30,000 daily riders through one of our densest and most job-rich regions.”