LA Metro Regional Connector Tunnel Construction, CA
Image credit: © Los Angeles County Metropolitan Transportation Authority - Regional Connector Transit Project (Photo: Gary Leonard)
Ninyo & Moore, a SOCOTEC Company, provided advanced geotechnical instrumentation and monitoring services for the Metro Regional Connector tunnel project in Los Angeles, California, ensuring safe construction of 1.9 miles of rail tunnels and three underground stations beneath downtown LA.
Key Information
Project Name: Metro Regional Connector Tunnel
Client: Los Angeles Metropolitan Transportation Authority c/o Arcadis
Location: Los Angeles, California
Services Provided: Geotechnical Instrumentation
The Challenge
Tunnel Construction Beneath a Thriving Urban Center
For decades, Los Angeles commuters faced a significant transit system bottleneck. Travelers moving between North/South and East/West rail lines were forced to transfer at 7th/Metro Station, adding 20-30 minutes to their daily commutes. This inefficiency discouraged mass transit use and contributed to LA's notorious traffic congestion and environmental challenges.
The LA Metro Regional Connector project presented complex engineering challenges:
Twin underground tunnels extending 1.9 miles and more than 50 feet below grade
Construction through densely populated downtown LA without disrupting businesses or residents
Three underground stations requiring excavation beneath existing infrastructure
Protection of sensitive structures, including the Walt Disney Concert Hall
Maintaining access to cultural and commercial districts like Little Tokyo during construction
The technical complexity was unprecedented. Tunnel boring machines had to navigate through variable ground conditions while engineers monitored potential impacts on existing buildings, utilities, and the ground surface above.
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The Solution
"The integration of real-time monitoring technology with experienced geotechnical interpretation creates a safety net that protects both the project and the community. This level of oversight is essential for managing the inherent uncertainties of underground construction."
The Results
Tunnel Construction Beneath a Thriving Urban Center
The geotechnical instrumentation and monitoring program provided LA Metro and the project team with reliable, real-time information to support construction activities across multiple underground worksites. By closely tracking ground surface movement and subsurface behavior, the team was able to respond proactively to changing conditions and maintain control during excavation.
The completed Metro Regional Connector now delivers measurable benefits to the Los Angeles transit system, including:
Up to 20–30 minutes saved on cross-county transit trips
A seamless connection between North/South and East/West rail lines
An estimated 17,000 additional daily transit trips, reducing congestion and emissions
Improved access to jobs, education, and cultural destinations across LA
The project demonstrates how well-executed geotechnical monitoring supports the successful delivery of complex infrastructure and transit system projects, particularly in dense urban environments with active rail service and sensitive surroundings.
“Major underground infrastructure projects depend on trust—in the data, in the monitoring systems, and in the engineers interpreting them. Our role was to help ensure that tunneling and excavation progressed safely, with confidence in the ground behavior at every stage.”
Image credit: © Los Angeles County Metropolitan Transportation Authority – Regional Connector Transit Project (Photo: Gary Leonard)
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