The first tunnel boring machine (TBM), named Elsie, broke through to the Los Angeles County Metropolitan Transportation Authority’s (L.A. Metro) Wilshire/La Cienega subway station in Beverly Hills.
It is the first of two TBMs that will reach this last station on Section 1 of the L.A. Metro D Line (Purple) Extension project.
Tunneling for the first four-mile section of the subway project is now two-thirds complete. More than 90 percent of the tunnels have been mined safely and L.A. 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-foot long TBM started west at the Wilshire/Fairfax station on May 29, 2020, and broke through to the Wilshire/La Cienega station site about one mile away on Feb. 25. L.A. Metro’s first TBM arrived at Wilshire/Fairfax on April 4, 2020.
Reaching this milestone is a significant win for L.A. Metro. Section 1 of project tunneling has presented challenges that have been successfully overcome. 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.
L.A. Metro’s TBMs were first lowered into the ground at the Wilshire/La Brea station site in the Miracle Mile area of Wilshire in October 2018. While advancing, the TBM tunneled about 60 feet per day. They worked five days a week, 20 hours a day.
L.A. 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 are also gasketed to make the joints between segments water- and gas-tight.
When tunneling is finished for this project section, both of L.A. Metro’s TBMs will have mined nearly half a million cubic yards of earth — the equivalent of filling 2.3 million bathtubs with dirt.
The TBMs were manufactured in Germany by Herrenknecht AG. L.A. Metro has contracted with Skanska Traylor Shea (STS), a joint venture to design and build the first section of the project.
The $9.3-billion Metro Purple Line Extension is a nine-mile underground subway project that will extend the Metro Purple Line from its terminus in Koreatown to Westwood/VA Hospital in West Los Angeles. Section 1 is expected to be completed in 2023, Section 2 in 2025 and Section 3 in 2027.
