TBM Hits Construction Milestone on LA Subway Extension

The 22-ft-diameter Elsie broke through into second of three stations April 6. Photo courtesy of Metro.

A 1,000-ton, 400-ft long tunnel boring machine (TBM) named “Elsie” reached a major milestone in a $9.3-billion Los Angeles subway extension program on April 6, breaking through into a planned station about 70 ft deep.

The Los Angeles Metropolitan Transportation Authority (Metro) announced the breakthrough on its official blog.

Elsie reached the Wilshire/Fairfax subway station near the La Brea Tar Pits in the Miracle Mile area of Los Angeles. It is the second station that the design-build team led by Skanska Traylor Shea (STS) has successfully reached via tunnel as part of Section 1 of the Metro Purple Line Extension Project. STS has a $1.6-billion contract for the $2.8-billion, 4-mile, 3-station section, scheduled for completion in 2023. The other two segments, each with two stations and approximately 2.5 miles long, are also under construction.

Elsie and her twin TBM Soyeon are 22-ft-diameter pressurized, closed-face machines. The tunnels are lined with precast concrete segments that are bolted together to form a ring.

According to Metro, the geological conditions are some of the most challenging, including tar sands and methane gas.

On April 3, Metro noted that Beverly Hills City Council decided in favor of Metro’s closure request of Wilshire Boulevard to help speed up construction of one of the stations.

Regarding COVID-19, Metro has said that its contractors are holding meetings outdoors whenever possible to maintain social distancing and using a roll call instead of passing around a sign-in sheet.

Aileen Cho, ENR's senior transportation editor, is a native of Los Angeles and recovering New Yorker. She studied English and theater at Occidental College, where a reporter teaching the one existing journalism course encouraged her to apply for the LA Times Minority Editing Training Program. Her journalism training led to her first stories about transportation, working as a cub reporter with the Greenwich Time. Her work has appeared in the Los Angeles Times and New York Times. Many of her experiences with engineers and contractors have inspired material for her alternative theater productions way, way off Broadway. For ENR, Aileen has traveled the world, clambering over bridges in China, touring an airport in Abu Dhabi and descending into dark subway tunnels in New York City. She is a regular at transportation conferences, where she finds that airport and mass transit engineers really know how to have fun. Aileen is always eager to hop on another flight because there are so many interesting projects and people, and she gets tired of throwing her cats off her computer in her home office in Long Beach, California. She is a very conflicted Mets/Dodgers fan.

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