Another innovation involved the location of a fan plant at the junction of the two lines coming into Little Tokyo, which will provide ventila- tion for the underground transit lines. WSP’s design analysis confirmed that this plan would work at this location, which resulted in a signifi - cant cost savings for the client. “When it was determined an additional tunnel ventilation fan plant was needed at that junction, it created an opportunity to use the TBM launch pit beneficially,” Hansmire said. “So rather than being back - filled, it became the perfect location for the fan plant, thus avoiding additional excavation.” Utility Protection and Relocation One major challenge during the construction of the tunnels was working around or relocating the existing underground water and util - ity infrastructure – some of which has been in place for more than a century, and none of which could afford to be disrupted. In addition, construction needed to minimize disruption of the downtown roads located directly above the worksites. “It has been our biggest issue, requiring some very careful coordina - tion as we balance the competing demands of utility work that requires closing lanes of traffic, while accommodating roadway traffic during those construction times,” Hansmire said. The significant success of the tunneling work was recognized in July with a national honor from the Underground Construction Association, which named the Regional Connector its Project of the Year . Environmental Justice Meeting the commitments made for mitigation of environmental im- pacts, particularly in the Little Tokyo neighborhood, posed challenges that kept the designers on their toes. Noise and vibration impact of construction and rail operations required extensive efforts to properly establish design-build performance requirements, and to work with the stakeholders and the final designer to ensure mitigation is achieved. “Connecting two existing transit lines that use systems equipment of different designs and ages demanded careful planning that required ex - pertise and experience in rail transit systems,” Hansmire said. “While the path was complicated, what was set in motion years ago when we started planning the project came together as expected, and with the tunnels completed and the underground stations being concreted, that vision is fast becoming a reality.” Stakeholders that will benefit from this extension include several major Los Angeles cultural institutions along the route, including the Walt Disney Concert Hall, the Colburn School and The Broad art museum. “The all-encompassing multidiscipline scope of the Regional Con - nector project has been a professionally rewarding opportunity to use my career-long project management and technical experience of many projects,” Hansmire said. “The Regional Connector project encompasses all technical disciplines for underground rail transit … everything is included.”
Construction image of the cavern. Photo: LA METRO
team – including SEM experts and experienced tunnel engineers from the contractor, the final designer, the construction manager, and LA Metro’s technical consultants – met daily to assure ground stability, ground support quality and performance, and adjacent building and utility responses. Upon completion of contact grouting in July 2020, the cavern excava - tion and the final lining installation completed successfully without exceeding predicted movements and imposing structural impacts on the adjacent structures. Commuters will notice something unusual at the Grand Av Arts/ Bunker Hill Station. For the first time, the LA Metro system is using high-speed elevators in a station instead of escalators. The new station, located about 100 feet below the surface, will feature six high-speed elevators with hoisting equipment located below the elevators—rather than above—to avoid the visual impact at the station entrance pavilion. At that depth, the elevators will transport passengers from the rail con- course level to the surface more quickly than escalators. The Broad and the Disney Concert Hall are in the background. Photo: LA METRO
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september 2020
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