The project will extend from the Metro Gold Line Little Tokyo/Arts District Station to the 7th Street/Metro Center Station in downtown Los Angeles. Once constructed, passengers will be able to transfer to Blue, Expo, Red, and Purple lines, bypassing Union Station and creating a one-seat ride for travel across Los Angeles County.
Traylor has primary responsibility for the twin tunnels which are 9,450 linear feet long and 20 feet, 7 inches in inner diameter. The project includes construction of three underground stations: Central, Broadway, and Hope Stations. The largest, Broadway, is 440 feet long, up to 90 feet deep, and 60 to 140 feet wide. The project also includes a connection to 7th and Flower Station. The entire alignment is within potentially gassy conditions.
The joint venture took over the in-progress advance utilities relocation contract as a change order at the outset of the project. Close coordination with local agencies and an extensive re-sequencing of the project was conducted to minimize overall schedule impact. All utilities along the alignment have been either relocated or protected in place, particularly along Broadway and Hope, where the utilities are large and numerous.
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 ft wide, 36 ft high and 300 ft long) and proximity to existing historic structures. The excavation was successfully completed in March 2019, two months ahead of schedule and within the acceptable building settlements of 0.5 inches.
The tunnel boring machine (TBM) is 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. Traylor Precast, LLC mobilized our Little Rock, California plant to make the precast concrete tunnel segments. 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). Winners were announced at an awards dinner in Miami held in conjunction with the Cutting Edge conference. This highly competitive award recognizes our innovation and ability to overcome challenges throughout the life of the project.