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LOS ANGELES (CNS) - Metro and elected officials Tuesday celebrated the completion of nine miles of tunneling for the D (Purple) Line Subway Extension Project that is intended to connect downtown with West Los Angeles.
The transit agency said the construction milestone was accomplished safely in one of the "densest and most geologically challenging urban corridors in the L.A. region."
"This safe completion of tunneling through this part of Los Angeles is a milestone in Metro's work to expand fast and reliable public transit across the region," L.A. Mayor Karen Bass, who is the chair of Metro's Board of Directors, said in a statement.
"When completed, the D Line extension will make Metro transit available to 53,300 more weekday riders traveling between downtown Los Angeles and the Westside."
According to Metro, contractors used the latest Tunnel Boring Machine (TBM) technology to excavate approximately 40-60 feet per day to help complete tunneling for the project. The 400-foot-long, 21-foot-diameter earth digging machines utilized closed face, pressurized TBM technology that minimize ground settlement during excavation.
The machines also lined the tunnel itself with pre-cast concrete segments that were bolted together to form secure rings, making them water- and gas-tight, preventing water and gas-related risks. The same technology was used on Metro's 2009 Eastside Extension Project.
"The D Line Subway Extension is one of the most complex engineering feats that Metro has undertaken," Lindsey Horvath, chair of the L.A. County Board of Supervisors and a Metro director, said in a statement.
"Its complexity is matched by the immense value the project will bring to Los Angeles when it opens and carries 30,000 daily riders through one of our densest and most job-rich regions."
Officials said that, during its five years of tunneling, the project faced many technical challenges, such as gassy ground, tar sands and abandoned oil wells. Near the La Brea Tar Pits, Metro's TBMs made their way through tar sands, and used horizontal directional drills to probe the earth so contractors could identify and remove potential objects before any TBM damage occurred.
Metro also used the same methods to identify and avoid unmapped and abandoned oil wells underneath Beverly Hills High School, officials said.
"We have proven yet again our capability to safely tunnel underneath a range of different structures as well as sensitive and historic sites," Metro CEO Stephanie Wiggins said in a statement.
Funding for the project came from transportation sales tax measures -- Measure R, approved by voters in 2008; Measure M, approved by voters in 2016; and federal funding.
Officials noted the next phase of the project will consist of completing seven new underground stations in Section 1, between Wilshire/Western and Wilshire/La Cienega; Section 2, between Wilshire/La Cienega and Century City; and Section 3, between Century City and Westwood.
The agency is aiming to open the Wilshire/Western underground stations in 2025, followed by the stations between Wilshire/La Cienega by 2026 and the underground station between Century City and Westwood by 2027.