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The Regional Connector Transit extends from the Metro Gold Line Little Tokyo/Arts District Station to the 7th Street/Metro Center Station in downtown Los Angeles, connecting passengers from Blue, Expo, and Gold lines. This project creates the second one-seat ride for travel across Downtown Los Angeles linking South North and East of greater LA.
Traylor held primary responsibility for the twin tunnels which are 9,450 linear feet long and 18 feet, 10 inches in inner diameter. The project included construction of three underground stations: Central, Broadway, and Hope Stations. The stations are up to 440 feet long, and 110 feet deep. The project also included a connection to 7th and Flower Station. The entire alignment is within potentially gassy conditions.
The cross passages and crossover caverns were constructed using Sequential Excavation Methods (SEM). The track crossover cavern presented its own challenges due to its size (58 feet wide, 36 feet high, and 300 feet long) and proximity to existing historic structures. The excavation was completed in March 2019, two months ahead of schedule and within the acceptable building settlements of 0.65 inches.
The tunnel boring machine (TBM) was a rebuild of one of the Herrenknecht TBMs from our University Link Light Rail Tunnels project in Seattle. It was modified to navigate a tighter curve radius to accommodate the three tight curves along the alignment.
The one machine, Angeli, was used to bore both tunnels. Each of the two launches were extremely challenging due an abrupt change in cover (from five to 20 feet) and the need to immediately mine downward at a 4.5% grade into a 600-foot horizontal curve. The team created a simulated earth paste to ensure pressure was maintained and relied on the TBM’s sophisticated computer system to successfully launch with negligible settlement. The mining was extremely productive, setting multiple records for Metro, and was completed more than three weeks early.
In November 2019, the team was awarded the International Tunneling Association’s (ITA) Project of the Year (between €50M and €500M). This highly competitive award recognized our innovation and ability to overcome challenges throughout the life of the project.