Purple Line (D Line) Extension Section 2 Construction Management Support Services
The Purple Line (D Line) Extension Section 2 Project (Project) is the second of three sections to be designed and constructed as part of the Los Angeles County Metropolitan Transportation Authority’s (LACMTA) Measure R Program. The program was approved by Los Angeles County voters in November 2008 and provides a half-cent sales tax to finance new transportation projects. In April 2012, the three sections of the Project were environmentally cleared and adopted by the LACMTA Board of Directors.
Section 2 will extend the future Wilshire/La Cienega Station, which is part of the Purple Line (D Line) Extension Section 1 Project currently under construction, to Century City. The Project is located entirely underground, primarily following Wilshire Boulevard, and includes the design and construction of approximately 2.59 miles of double-track heavy rail, two new stations, as well as the purchase of 20 heavy rail vehicles. The Beverly Drive Station is within the jurisdiction of the City of Beverly Hills, and the Century City Station is within the jurisdiction of the City of Los Angeles. The Project also includes train controls, signals, traffic controls, communications, traction power supply and distribution, fare collection systems and equipment, acquisition of rights-of-way, and utility relocations.
- 2.5 miles of earth pressure balance (EPB) twin bored tunnels and cross passages
- Two new underground stations
Scope of Work
Delve Underground, as part of the Purple Line 2 Construction Management Support Services (CMSS) Joint Venture of AECOM/Safeworks/TEC/Morgner Construction, is the lead tunneling subconsultant on the Project. Currently, Delve Underground is providing CMSS through augmented construction management personnel, including construction manager, principal technical specialists, tunnels/shaft assistant construction managers, office engineers, changes evaluation, geotechnical engineer instrumentation specialist, and tunnel inspectors.
Our engineering services include field management of the CMSS team, contract administration, technical review and evaluation of all underground construction submittals and inspection and monitoring of the tunnel and cross passage excavation, seismic zone lining installation, and installation of guideway track. In addition to the main design-build scope, which encompasses design, excavation, concrete, architectural, mechanical, electrical, systems, and restoration work, the project also involves advanced utility relocations managed by various utility agencies.
Challenges and Innovations
The project encountered several significant challenges during tunneling operations. These included tunneling beneath Beverly Hills High School, excavating under major thoroughfares such as Wilshire Boulevard, performing cutterhead repairs on one of the TBMs after approximately 1,300 feet of excavation, navigating through the Wilshire/Rodeo Station, and connecting the alignment with the WLPE Section 1 tunnels, which was successfully completed.
The tunnel alignment was monitored by an extensive geotechnical instrumentation monitoring program, and the tunnel excavation was completed within the anticipated response parameters, with no noticeable ground movement at the surface.
Additionally, a special tunnel lining section was engineered to accommodate potential displacement across the Santa Monica seismic fault zone. This design ensures the tunnels will maintain structural integrity in the event of a seismic event.
