LA Metro completes five years of tunneling; addinig nine miles on D Line

Los Angeles Construction News staff writer

The Los Angeles County Metropolitan Transportation Authority (Metro) has completed tunneling for the D Line Subway Extension Project that will connect downtown L.A. with West L.A., a major construction milestone accomplished safely in one of the densest and most geologically challenging urban corridors.

“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,” said Mayor Karen Bass. “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.

“Thank you to all of the construction workers who have given their time and talent to successfully complete the tunneling.”

Through a joint venture with Skanska-Traylor-Shea and Tutor-Perini/O&G crews will complete 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 end of tunneling work on this project is a triumph of engineering, planning and execution. Our construction team undertook a painstaking process that helped us keep everyone in these communities safe and deliver a better project for the people of L.A. County,” said Stephanie Wiggins, Metro CEO. “We have proven yet again our capability to safely tunnel underneath a range of different structures as well as sensitive and historic sites.”

Contractors used the latest tunnel boring machine (TBM) to excavate 40 to 60 feet per day. The 400 foot-long, 21 foot-diameter earth digging machines used closed face, pressurized TBM technology that minimizes ground settlement during excavation. The machines also lined the tunnel itself with precast concrete segments that were bolted together to form secure rings making them water- and gas-tight, preventing water and gas-related risks. This same TBM technology was successfully employed on Metro’s 2009 Eastside Extension Project.

“The D Line Subway Extension is one of the most complex engineering feats that Metro has undertaken,” said Lindsey Horvath, Chair of the LA County Board of Supervisors and Metro Board Member. “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.”

During its five years of tunneling, construction crews overcame many technical challenges like gassy ground, tar sands and abandoned oil wells. Near the La Brea Tarpits, for example, Metro’s advanced TBMs made their way through tar sands, and used horizontal directional drillings to probe the earth so contractors could identify and remove potential objects before any TBM damage occurred. Metro also safely used the same methods to identify and avoid unmapped and abandoned oil wells underneath Beverly Hills High School.

“Now that tunneling is complete, it won’t be long before Metro completes this mega-project and makes it possible for everyone to travel from downtown L.A. to West L.A. in under 30 minutes,” said Katy Yaroslavsky, L.A. City Council Member and Metro Board Member. “This subway extension will catalyze ridership on the entire Metro System in the years ahead, bringing many thousands of new riders throughout Metro’s transit system.”

Forecasted openings are 2025 for Section 1, 2026 for Section 2 and 2027 for Section 3 of the project.