Two TBMs (Tunnel Boring Machines) employed by the Los Angeles County Metropolitan Transportation Authority (Metro)—one named Soyeon, the other, Elsie—have completed many months of work on Section 1 of the $9.3 billion, nine-mile Metro Purple Line Extension subway project by reaching the future Wilshire/Fairfax station near the La Brea Tar Pits in the Miracle Mile.
Tunneling for the first three miles of the four-mile initial section is now complete. Soyeon started at the Wilshire/La Brea station in October 2019 and broke through the eastern side of the planned Wilshire/Fairfax station site about one mile away on May 21. Elsie broke through to Wilshire/Fairfax on April 4.
The 1,000-ton, 400-foot-long TBMs, manufactured in Germany by Herrenknecht AG, were lowered into an excavation pit at Metro’s Wilshire/La Brea station site in the Miracle Mile area of Wilshire in October 2018 and began advancing about 60 feet per day. They worked five days per week, 20 hours a day. Soyeon and Elsie 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 completed for Section 1, both TBMs will have mined nearly a half-million cubic yards of earth, “the equivalent of filling 2.3 million bathtubs with dirt,” Metro notes. The TBMs will now head farther west to the final Section 1 station at Wilshire/La Cienega. They are expected to reach the end of this first four-mile tunneling section in Beverly Hills this fall.
The Metro Purple Line Extension will extend the subway from its existing terminus in Koreatown to Westwood/VA Hospital in West Los Angeles. Metro has contracted with Skanska Traylor Shea (STS), a joint venture to design and build Section 1, which is expected to be completed in 2023. Section 2 will follow in 2025; Section 3 in 2027.
“Reaching this dual milestone is a significant win for Metro,” the agency says. “The underground soil conditions in this area of Los Angeles represent some of the most challenging for the entire project. The agency’s modern, high-tech TBMs have mined through a unique combination of soils and geologic conditions, including tar sands and methane gas. The breakthrough also marks another milepost in the decades-long effort to extend L.A.’s subway farther west underneath Wilshire Boulevard, one of the busiest and most congested urban thoroughfares in the United States.”
“This has been an enormously complex operation that Metro and its contractor Skanska Traylor Shea have successfully conducted,” said city of Inglewood Mayor and Metro Board Chair James T. Butts. “When this project is ultimately completed, we will have fast, frequent and reliable subway service connecting downtown L.A. and West L.A. in just 25 minutes. That will be a game-changer for all of L.A. County.”
“We are proving once again that we can successfully mine through some of the most challenging conditions that any subway project in the world is likely to face,” said Metro CEO Phillip A. Washington. “We have a world-class project team that has extensive tunneling expertise. We are well on our way to delivering this vitally important transit project to taxpayers.”