Los Angeles — July 2, 2019 — Recently, the Los Angeles County Metropolitan Transportation Authority (Metro) reached a major milestone in its Metro Regional Connector project, completing the largest cross-section of tunnel in the city. This will allow trains on the new light-rail system to switch tracks seamlessly underground, while facilitating Metro operations.
When complete, the Metro Regional Connector will feature a 1.9-mile light-rail system designed to improve mobility in downtown Los Angeles. The Regional Connector is a key part of Metro’s Twenty-Eight by ’28 Initiative, a highlighted list of transit and mobility projects for potential completion by the 2028 Summer Olympic and Paralympic Games.
“We are honored to continue our work with L.A. Metro to prepare the city not only for the influx of visitors during the 2028 Games, but to improve transit connectivity and mobility for all Los Angeles residents,” said Macaria Flores, Arcadis City Executive in Los Angeles.
Contracted as Metro’s construction manager on the $1.75 billion project, Arcadis monitored design compliance, provided independent verification and managed the mining and construction of the cavern.
The tunneled cavern measures 287 feet long by 58 feet wide by 36 feet high and sits beneath existing building foundations and major utilities. To complete this mined crossover tunnel (a complex engineering feat), the design-build team adopted a technique called sequential excavation method (SEM) — also known as New Austrian Tunneling Method (NATM).
The method allows for the construction of large and complex caverns using conventional equipment and materials, with very little surface settlement. It’s the preferred tunneling method in earthquake-prone areas.
“The complexity of using a mining application such as SEM demonstrates how collaboration between the designer, contractor, construction manager and infrastructure owner is crucial to maintaining safety and construction performance,” said Dominic Cerulli, Arcadis senior project manager and SEM cavern resident engineer on the Regional Connector project.