Regional Connector, Cross Over Cavern, Los Angeles


Los Angeles County, Metropolitan Transportation Authority


Regional Connector Constructors (Skanska - Traylor Arbeitsgemeinschaft)

Consultant for SEM/ NATM: Beton- und Monierbau USA, Inc.
(100 % subsidiary of BeMo Tunnelling GmbH, Austria)
1 SEM/ NATM – Senior Engineer, 1 SEM/ NATM - Superintendent
during cavern excavation on site for approx. 10 – 12 months

Project location

Los Angeles

Start of construction


End of construction


Project total value

approx. 0.85 million €


Fernando Formations

Technical Data

• Provision of key personnel during SEM excavation and support
of a cross over cavern, double side drift tunnel method
• 1 pipe umbrella
Length: 60 feet
2 layers of in total 54 pipes
• Measures of cavern:
Length: 287.22 feet (87.54 m)
Width approx. 58 feet (17.60 m)
Height approx. 36 feet (11.00 m)
• Low overburden/ excavation underneath a lot of installations
(storm sewer, gas, water, sewage etc.)
• Urban environment in downtown Los Angeles
(underneath W 2nd Street between S. Spring Street
and S. Main Street)

Further project related information

• Very challenging excavation
• first large-scale application of SEM/ NATM in Los Angeles