Through Metro’s preliminary engineering phase, engineers from both Metro and JMB worked together to ensure that conceptually, the proj - ects could work together, and changes could be made to each party’s designs so the two projects would complement one another. During the coordination process, several challenges were addressed, including: • the integration of changes from one project into the other; • finding a suitable area available for construction staging, since both projects were planned to progress simultaneously; • planning for two mega structures to be built independently of each other, since at the design stage it was not clear which project would start and complete construction first; and • ensuring through real estate easements that all parties would have the access needed to different areas of the property both in the temporary condition (during construction) and in the permanent condition. These challenges were overcome in part by regular meetings, good coordination, and sharing electronic files, including 3D BIM models regularly. Additionally, in this joint development process both parties collaborated closely so that the designers of the high-rise understood the needs of an underground heavy rail subway system and vice-versa. “Without that understanding, it would have been much more challeng - ing to undertake,” Kothari said. Section 3 Challenge For Section 3, the most critical element for constructing the project was identifying the launch site for the Tunnel Boring Machine. The site originally identified as the best location for the staging area was on U.S. Army Reserve property at 1250 Federal Avenue but was later moved to the VA campus. This change required extensive collaboration with representatives of the VA to make it possible. “The site selected was located in a historic district, protected by the National Historic Preservation Act, thereby requiring collaboration with the Federal Transit Administration and VA’s historic preservation staff,” Kothari said. “VA approval of the environmental documenta - tion prepared for the new construction site was also required, thereby requiring coordination with VA on drafts of the documentation.” Negotiations proved successful, and all agreements with the VA were completed, allowing for a timely start to construction. Technical Innovations The emergency ventilation design implemented many innovative solu- tions to deal with Metro requirements to control smoke and heat that could potentially be generated by a serious rail car fire that generates a fire heat release rate of 86,528,000 BTU/hour. “The need to control the smoke and heat generated by such a large fire required innovative solutions,” Kothari said. To meet this stringent criteria, the station design incorporated high ceil- ings in the platform areas that act as a reservoir to contain smoke dur-
This 2.6-mile Section 2 extension includes additional stations at Wilshire/ Rodeo and Century City Constellation. Construction is 49 percent com - pleted, and revenue service on Section 2 is expected in 2025. In May 2021, a groundbreaking ceremony was held for Section 3 of the project. Construction is currently 34 percent complete and consists of another 2.6-mile stretch of twin-bored tunnel that will include sta - tions at Westwood/UCLA and a new terminus station at Westwood/VA Hospital in West Los Angeles. Section 3 is scheduled for completion in 2027. “The presence of an active fault line on both Sections 2 and 3 align - ments required our team to locate fault zones and design the tunnels to remain safe, should a fault rupture occur,” Kothari said. “WSP pro - vided the preliminary geotechnical investigations and crossing designs and worked alongside the design builder during final investigation and design of fault crossings.” The contractor’s final design program included large-scale laboratory testing to confirm the findings of the design assumptions. The project team faced a few other hurdles at Sections 2 and 3. Section 2 Challenge During the planning stages of this project, there were two possible locations for the entrance to the Century City Constellation Station, both on corners of the busy intersection of Constellation Boulevard and Avenue of the Stars. Ultimately, Metro determined the best option would be an entrance on the northeast corner of the intersection, on an undeveloped property owned by JMB Realty (JMB). In working with JMB to secure the easement, Metro became aware that the property owner had plans to develop the vacant land into a development with high-rise towers. Metro saw this as an opportunity to work with JMB in a mutually beneficial joint development agreement. The elements of the Metro entrance that need to be placed on the pri - vate property are the entrance plaza at the surface and the underground portions of the entrance, which connect patrons to the actual subway station, and additionally some ventilation gratings and a set of emer- gency exit stairs.
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csengineermag.com
January 2023
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