The Los Angeles County Metropolitan Transportation Authority (Metro) announced that its first tunnel boring machine (TBM), named Elsie, has officially broken through to the Wilshire/La Cienega subway station site in Beverly Hills.
It is the first of two TBMs that will reach this last station on Section 1 of the Metro Purple (D) Line Extension Project.
Tunneling for the first 4-mile section of the project is now two-thirds complete. More than 90 percent of the tunnels have been mined safely and Metro anticipates completing tunnel mining this summer. Excavation for all three subway station boxes beneath Wilshire Boulevard has been completed.
Elsie, the 1,000-ton, 400-ft-long TBM, started west at the Wilshire/Fairfax station on May 29, 2020, and broke through to the Wilshire/La Cienega station site about 1 mile away on Feb. 25. Metro’s first TBM Elsie arrived at Wilshire/Fairfax on April 4.
Reaching this milestone is a significant win for Metro. Section 1 of project tunneling has presented challenges that have been successfully overcome by the project. En route to Wilshire/La Cienega, the agency’s modern, high-tech TBMs have mined through a unique combination of soils and geologic conditions, including tar sands and methane gas.
“Metro has reached yet another milestone as it works to bring fast, frequent, and reliable subway service to the Westside,” said Los Angeles Mayor and Metro Board Chair Eric Garcetti. “Tunneling to Wilshire/La Cienega is a big step toward completing the first section to the Miracle Mile and Beverly Hills and connecting Angelenos to the many destinations in both of those communities.”
Metro’s TBMs were first lowered into the ground at Metro’s Wilshire/La Brea station site in the Miracle Mile area of Wilshire in October 2018. While advancing, the TBM tunneled about 60 ft per day. They worked five days a week, 20 hours a day.
Metro’s TBMs are pressurized, closed-face machines that minimize ground settlement during excavation. The tunnel is lined with precast concrete segments that are bolted together to form a ring. Segments also are gasketed to make the joints between segments water- and gas-tight.
When tunneling is finished for this project section, both of Metro’s TBMs will have mined nearly half a million cu yd of earth—the equivalent of filling 2.3 million bathtubs with dirt.
“This project is easily the most complex engineering feat in the modern history of L.A. Metro Rail construction,” said Metro CEO Phillip A. Washington. “The subway travels through some of L.A. County’s most densely urbanized neighborhoods and beneath some of our region’s most challenging geologic conditions. I’m glad that our project team has had such great success in tunneling through this area.”
The TBMs were manufactured in Germany by Herrenknecht AG. Metro has contracted with Skanska Traylor Shea (STS), a joint venture to design and build the first section of the project.
The Metro Purple (D) Line Extension is a 9-mile underground subway project that will extend the line from its terminus in Koreatown to Westwood/VA Hospital in West Los Angeles.
For photos and video of the Wilshire/La Cienega TBM breakthrough or for more information on the Purple Line Extension Project, go to www.metro.net/purplelineext.