Tunnel Excavation Completed on LA Metro’s Westside Purple Line Extension Section 2

Project Update

January 12, 2023 marked an important mile­-stone on Los Angeles County Metropolitan Transportation Authority’s (LA Metro) Westside Purple Line Extension (WPLE) Section 2 Project, when the second and final tunnel boring machine (TBM) successfully completed its journey and arrived at the interface with WLPE Section 1. This milestone represented the conclusion of tunnel excavation of the 2.59 miles (4.17 km) of twin-bore tunnels that make up Section 2 of the overall project.

Tunneling commenced in April 2020 and experienced several notable challenges during its duration. These included proceeding under the Beverly Hills High School, excavation under several busy thoroughfares (including Wilshire Boulevard), repair of one the TBM’s cutterheads after 1,300 feet of excavation, passage through the Wilshire/Rodeo Station, and the successful alignment connection with the WLPE Section 1 tunnels. The tunnel alignment was monitored by an extensive geotechnical instrumentation monitoring program, and the tunnel excavation was completed within the anticipated response parameters with no noticeable ground movement at surface.

Each TBM excavated a total of approximately 11,540 feet (3,517 m), with an average daily production rate of 22 feet and a best daily advance of 75.2 ft (22.1 m). Traditional segmental lining, with double gaskets, was typically installed and a special lining, consisting of continuous hoop reinforcing, was installed in the Santa Monica seismic fault zone.

There will be a total of 15 cross passages between the two tunnels. Excavation of these structures, 14 of which will be constructed by the Sequential Excavation Method (SEM), commenced in late 2022 and is expected to be completed by the end of 2023.

The design-build contract was awarded to a joint venture between Tutor Perini and O&G Industries (TPOG) in 2017, with construction scheduled to be completed by 2025. The Purple Line 2 CM Partners Joint Venture—led by AECOM, SafeworkCM, Morgner and TEC, with Delve Underground as the lead tunneling and geotechnical consultant—is providing construction management support services to LA Metro.