Tunneling on LACMTA Purple Line Extension Project begins

Written by Kyra Senese, Managing Editor, Railway Track & Structures
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Project map of the Purple Line | Image: LACMTA

The Los Angeles County Metropolitan Transportation Authority (LACMTA) has launched tunneling work on its Purple Line subway extension.

In what officials described Oct. 17 as a key milestone for construction of the first segment of the LACMTA Purple Line Extension Project, twin tunnel boring machines (TBMs), named Elsie and Soyeon, will start by tunneling parallel underground sections of the system between the planned Wilshire/La Brea Station and the existing Wilshire/Western Purple Line terminus.

Each of the TBMs weigh in at 1,200 tons, measuring 450 feet in length, have a diameter of 21.8 feet and will simultaneously excavate about 60 feet per day in the twin tunnels during the next two years.

LACMTA Board Chair and L.A. County Supervisor Sheila Kuehl also noted the importance of the tunneling work for the Purple Line Extension.

“When completed, this line will get our riders from the Westside to Downtown and back, helping them to skip the congested east-west corridors along Wilshire and Santa Monica Boulevards,” Kuehl said.

The TBMs are set to work in tandem, with Elsie expected to trail Soyeon by roughly 150 feet. The machines will be separated by about 16 feet of soil as the cutter heads grind away the soil in their path. Hydraulic arms will be in operation at the rear of the machines to insert concrete segments into the newly mined tunnels, which will further propel the machines forward.

LACMTA broke ground on the first section of the project in November 2014, measuring at 3.92 miles, which will begin at the existing Wilshire/Western Station and reach new stations currently being excavated at Wilshire/La Brea, Wilshire/Fairfax and Wilshire/La Cienega, LACMTA said.

“The Purple Line Extension Project is an important part of Metro’s ambitious plan to improve and expand mobility throughout Los Angeles County and will serve our region’s second-largest job center,” said LACMTA CEO Phillip A. Washington. “This is one of the most significant transit projects we plan to deliver to the public before the Summer Olympic and Paralympic games arrive in Los Angeles in 2028.”

The $2.82-billion section of the project is supported through funds allocated by Measure R, in addition to federal funding. Stantec, an engineering firm offering design and consulting services, will manage the construction of this section.

The first segment of the Purple Line Extension Project is set for operation in 2023, with the second section to Century City to be ready in 2025, officials said. The final section serving the Westwood/VA Hospital is set to be operational in 2026.

Upon its completion, the Purple Line extension will transport passengers between downtown Los Angeles and Westwood in 25 minutes, LACMTA said.

The Purple Line extension is expected to serve 59,000 daily passengers, including 17,000 new customers.

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