L.A. Metro’s Purple Line Extension Project Will Reshape Daily Commute for Los Angeles

When the world’s top athletes descend upon Los Angeles for the 2028 Summer Olympic Games, a new underground rail line will provide a critical means of transportation to many of the venues for athletes and spectators alike.

The $9.5 billion Metro Purple Line Extension Project is a nine-mile heavy rail line that will operate as an extension of Los Angeles Metro’s Purple Line from its current terminus at Wilshire/Western Station to a new western terminus in West Los Angeles near the Veterans Administration (VA) West Los Angeles Medical Center in Westwood. The full project, which is divided into three sections, is on target for completion before Los Angeles hosts the 2028 Olympic Games.

The subway extension will connect the D Line (Purple) to several major destinations, with stops near the La Brea Tar Pits and the Los Angeles County Museum of Art, Beverly Hills and the campus of UCLA (where the Olympic Village will be located when Los Angeles hosts the 2028 Summer Olympic Games.)

“The nine-mile extension will provide an easy, reliable means of transportation to the Westside of Los Angeles, the second-largest job and population center in the entire region,” said Ashok Kothari, WSP USA project director. “This project will improve mobility and reliability, transit service, and access to major activity and employment centers. During the Olympics, it will provide a critical means of transportation for athletes and international spectators.”

WSP has been providing environmental and engineering services to the Los Angeles County Metropolitan Transportation Authority (Metro) since early planning studies began in 2007.The firm’s responsibilities have included the preparation of the alternatives analysis, environmental impact and funding reports, preliminary engineering, request for proposal (RFP) documents and design support during construction services including systems testing and commissioning.

“Activity centers in the study area are served by the city’s infamously congested roadway network, which is forecasted to deteriorate further with increases in population and employment,” Kothari said. 

The final environmental impact statement and environmental impact report (EIS/EIR), which was prepared by WSP, determined that when the project is completed, travel time from the existing end of the Purple Line, Wilshire/Western Station, to the new Westwood/VA Station will drop from an average of 46 minutes by car to just 15 minutes by subway.

Section 1 

Groundbreaking was held in November 2014 for Section 1, a twin-bored, four-mile tunnel extending from the existing Wilshire/Western Station and includes underground stations at Wilshire/La Brea, Wilshire/Fairfax and Wilshire/La Cienega. 

With design work complete and construction having reached the 75 percent mark, Section 1 is on track for opening in 2024.

To celebrate the 50 percent completion milestone for Section 1, a “Halfway Completion Ceremony” was held on June 2, 2019 at the La Brea Tar Pits area, attended by local officials, members of the design and construction team, and the local community. 

It was an appropriate location for the event, as the unique area posed some of the biggest geologic challenges for the extension project.

Section 1 Challenges – Construction in the La Brea Tar Pits Area

Challenges associated with the La Brea tar pit area included the need for careful, accurate assessment of the “tar sand” properties for tunnel and station design, determination of the most appropriate construction methods in the gassy ground and awareness of the potential for encountering Ice Age-era fossils, similar to those displayed at the La Brea Tar Pits and Museum in the Wilshire/Fairfax Station area.

To investigate this area prior to construction, in addition to geotechnical borings, WSP designed an exploratory shaft to provide information to designers and contractors on soil properties, construction methods in these conditions, gas monitoring data and construction methods to preserve large fossils should they be encountered. Contractors visited the shaft excavation during the Section 1 early procurement phase.

Sections 2 and 3

To stay on target for a fully operational subway extension in 2027, work on the second and third sections of the project is already well under way. A groundbreaking ceremony for Section 2 was held in February 2018. 

This 2.6-mile Section 2 extension includes additional stations at Wilshire/Rodeo and Century City Constellation. Construction is 49 percent completed, 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 stations 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 alignments required our team to locate fault zones and design the tunnels to remain safe, should a fault rupture occur,” Kothari said. “WSP provided 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 private 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 emergency exit stairs.

Through Metro’s preliminary engineering phase, engineers from both Metro and JMB worked together to ensure that conceptually, the projects 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 challenging 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 documentation 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 solutions 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 ceilings in the platform areas that act as a reservoir to contain smoke during the early stages of a fire. Downstand enclosures around the vertical circulation (stairway and escalator) openings are designed to prevent smoke from rising into the concourse, allowing those areas to remain free of smoke and allow patrons to move to a point of safety.

A large over-platform exhaust (OPE) duct/plenum will be placed over the platform with chimneys alongside the concourse. This design was verified using computational fluid dynamics (CFD) to analyze the convey smoke from an under-concourse train fire into the OPE. 

To address Metro’s concerns for protecting patrons during a fire in the crossover, during the final stages of design an internal exhaust plenum connecting the tunnel end of the crossover to the emergency ventilation fan plenum was added.

“This will allow for smoke extraction at either end of the crossover, permitting evacuation in either direction after identification of the location of the railcar fire,” Kothari said.

Other technology incorporated during the Advance Preliminary Engineering phase was the use of platform heat detectors to quickly activate the emergency ventilation system and the use of Revit 3D design software to model the station, which in turn was used to prepare the CFD model.

“Many of these innovative ideas came as a need to solve unique problems created by the large fire and were initiated by WSP’s ventilation expert William Kennedy, who passed away in 2012,” Kothari said. “It was designed in conjunction with the Purple Line Extension design team, with assistance from WSP’s modeling team based in New York City.”

Environmental Considerations

Aware of the need to minimize any negative environmental impact, the design and construction team have taken measures whenever possible to create opportunities for improvements to the communities located along the new extension. 

The maintenance of way (MOW) building constructed as part of the project is located on a brownfield site that was successfully remediated by removing underground storage tanks and contaminated soil. Additionally, the project team actively treated an underground hydrocarbon plume left by the former industrial facility.

“We engaged a third-party commissioning agent to oversee the integration of the various mechanical, electrical and plumbing systems to maximize the efficiency and performance of the MOW building management system,” Kothari said. “The building features a 353-kilowatt photovoltaic system over rooftop parking, which was a major contributor to achieving a LEED Gold certification from the U.S. Green Building Council.”

The project team also incorporated a value engineering proposal (VEP) proposed by the Section 2 Design/Build Contractor, Tutor Perini/O&G JV into the tunnel segments, which allowed the use of a specially reinforced concrete segmental lining in lieu of a steel segmental lining through an area of seismic faults. 

The special concrete lining consists of hoop reinforcement with continuous bars, dense rebar mats, additional steel fibers and the installation of interior bands to mitigate soil and water ingress in the event of a seismic event. The VEP was a collaborative effort between Metro, WSP and the contractor.

Communication Tools

The use of building information modeling (BIM) has added value to the project through near-real-time collaboration amongst all the many disciplines of the design teams and with the client which accelerated the design development process. 

“Modular stations were envisioned to improve system-wide uniformity, and BIM facilitated the highly-coordinated development of these modules which were then strategically combined based on site-specific constraints,” Kothari said. “BIM was used to model existing conditions, such as building foundations and utilities, which led to a much more advanced preliminary design since conflicts with the proposed design were identified and resolved early.”

BIM also helped the design team achieve Metro’s goal of constructing columnless platforms for all stations along the Purple Line Extension.

“BIM has been an invaluable communication tool used to interface with the client, stakeholders, adjacent property owners, third-party agencies, and the community,” Kothari said.

Metro will finish the project with a complex record model and a loaded parametric database, which can be used for decades to come in the operation and maintenance of its facilities.

Communication has been a critical asset for the project, not just between team members, but to keep the community apprised of the progress as well. 

The WSP project team co-located with client staff in an integrated project office (IPO) to facilitate its ability to respond to the client and project’s needs and simplify communication.

“It was very important to the client to have all the project staff in one location as soon as possible and the IPO has enabled us to respond to client requests quickly,” Kothari said. “Our team is available immediately to meet with the client to resolve any issues that arise or respond to any special requests.” Sameh Ghaly, LA Metro senior executive manager for project management, praised the ongoing collaboration the agency has had with Kothari since the advent of his preliminary engineering work on the project in 2010.

“Ashok is one of the most accomplished global mega-project managers in the transportation industry, and under his leadership, the team has provided critical engineering and environmental support to LA Metro, including environmental impact and funding reports, preliminary and advanced engineering, preparation of RFP documents and design support during construction.” 

The WSP project team provides technical support for community outreach meetings and presentations and third party coordination meetings and presentations.

“Public support for the Metro Purple Line Extension Project remains high,” he said. “Metro has a robust Construction Relations unit that disseminates up-to-date information about project progress and responds to community concerns during construction.”

WSP technical staff have assisted Metro with presentations at community meetings where they have been able to answer the community’s questions related to air quality, noise, subsurface conditions and tunneling.  

“Because WSP also prepared the project’s environmental documents and technical requirements, we could explain the construction contract requirements, the criteria for their development, and how Metro would be monitoring construction to protect the community,” Kothari said.

Progress During Pandemic 

Despite the challenges posed in 2020-21 by the COVID-19 pandemic, Kothari said that construction progress on the Metro Purple Line Extension Project has not been negatively impacted. During the “Safer at Home” order in Los Angeles County, services provided by Metro were classified as essential services and construction work was exempted from the order.

“The initial challenge was to put a program in place to rigorously monitor safety procedures at the office and in the field and ensure that anyone who tested positive self-quarantined immediately and reported their condition to their supervisor so that offices were closed and that spaces could be sanitized,” Kothari said. “Additionally, project team members were allowed to telecommute, if feasible, based on their responsibilities. Due to this program, few illnesses were reported at the work sites.”

A benefit from the countywide order was the reduction in traffic around the work sites. For example, on Section 2 at the location of the Wilshire/Rodeo Station, the City of Beverly Hills approved a full closure of Wilshire Boulevard for three and a half blocks for over two months to expedite piling and decking activities. 

“The project was able to complete the decking with significantly fewer impacts to local business and shave months off the schedule because this activity was originally scheduled to occur over weekends between August 2020 through January 2021,” Kothari said.

Mentoring/Protégé Program

WSP established a mentoring/protégé program on Section 3 of the project with Metro’s support in June 2016, designed to benefit the sub consultant firms working with us on the project. The goals of the program were to:

• Assist small businesses, with consideration given to minority-, woman-, disabled veteran-owned and other historically underutilized businesses (HUBs), to increase capacity and access to opportunities to grow their business;

• Create strategic relationships with key smaller firms and establish a go-to relationship between WSP and protégé firms;

• Use WSP’s global resources for knowledge-sharing with subconsultants; and 

• Foster the establishment of long-term business relationships between protégé firms and WSP.

Kothari is grateful for the opportunity to participate in the creation of a major transportation project that will transform mobility options and  quality of life for Los Angeles’ commuters.

“The depth of resources and expertise WSP provides has been a significant benefit to our client on the project, and I have been honored to lead a talented and dedicated team of professionals along the way,” Kothari said. “You feel an extra sense of pride when you play a role designing something so critical to the people who live in your own hometown.”

*This article was originally published in May 2022