The Los Angeles County Metropolitan Transportation Authority (LA Metro) has completed tunnelling for the D Line Subway Extension Project.

Over the last five years, this infrastructure project has added nine miles to the LA Metro D line connecting downtown LA with West LA.

Mayor Bass celebrates the end of tunnelling© LA Metro

Karen Bass, L.A. City Mayor and Metro Board Chair said:

“This safe completion of tunnelling through this part of Los Angeles is a milestone in Metro’s work to expand fast and reliable public transit across the region. When completed, the D Line extension will make Metro transit available to 53,300 more weekday riders travelling 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 tunnelling.”

Throughout this work, contractors used two Tunnel Boring Machines (TBM) to excavate approximately 40-60 feet of tunnel each day.

The 400-foot-long, 21-foot-diameter machines used closed-face, pressurised TBM technology that minimises ground settlement during excavation.

The machines also lined the tunnel with precast concrete segments that were bolted together to form secure rings that are both water- and gas-tight.

A TBM cutterhead at the future La Brea station© LA Metro

During the five years of tunnelling, Metro overcame several technical challenges such as gassy ground, tar sands and abandoned oil wells.

Lindsey Horvath, Chair of the LA County Board of Supervisors and Metro Board Member said:

“The D Line Subway Extension is one of the most complex engineering feats that Metro has undertaken. 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.”

With the completion of tunnelling, Metro will now continue to work with Skanska-Traylor-Shea and Tutor-Perini/O&G to complete seven new underground stations along the route.

The D Line Subway Extension Project© LA Metro

Section 1 of the extension is scheduled to open in 2025 between Wilshire/Western and Wilshire/La Cienega. This will be followed by Section 2 between Wilshire/La Cienega and Century City in 2026 and Section 3 between Century City and Westwood in 2027.

Katy Yaroslavsky, L.A. City Council Member and Metro Board Member said:

“Now that tunnelling 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. “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.”