The I-405 Sepulveda Pass Improvements Project is a highway widening development being undertaken by California Department of Transportation (Caltrans) in collaboration with the Orange County Transportation Authority (OCTA), for its owner Los Angeles County Metropolitan Transportation Authority (LACMTA). The total investment on the project is expected to reach $1.03bn.

“The construction works are being carried out with a workforce of 18,000 people.”

Construction works for the interstate highway passage started in 2009 and the project is scheduled to be realised in 2014. The construction works are being carried out with a workforce of 18,000 people.

The project is being implemented on a design-build basis with the main contractor being Kiewit Infrastructure West (Kiewit). It is currently the largest design-build highway project in Southern California by budget.

Sepulveda Pass improvement project details

The project chiefly involves the widening of the San Diego Freeway / Interstate 405 (I-405) by adding a northbound high-occupancy vehicle (HOV) lane measuring 10 miles at the Sepulveda Pass section stretching from Santa Monica Freeway (I-10) to the Ventura Freeway (US 101).

Additional works under the project include the demolition and replacement of three bridges, realigning 27 on and off-ramps, widening of 13 existing underpasses and structures, and construction of about 18mi of retaining wall and sound wall. Improvements will also be made to the adjacent city streets.

Some of the bridges that will be demolished and reconstructed under the project include the Skirball Center Dr Bridge, Sunset Bridge and Mulholland Dr Bridge. Up to eight ramps will be reconstructed along the Wilshire Bl interchange.

Benefits of improving the interstate highway passage

The project will cut down travel times for 300,000 vehicles per day along the Interstate 405, enhance driving safety on the highway, reduce pollution and promote ridesharing.

It is being constructed to overcome the existing and future traffic congestion on the interstate highway.

Construction of the Sepulveda Pass improvements

All the structures under the project are being designed to meet the latest seismic standards.

As of June 2013, three of the eight Wilshire Bl/I-405 ramps were completed. The Sepulveda Pass section will be widened by cutting the hillside and constructing new retaining walls along the west side of the street. It will add a new signalised intersection and a northbound bike lane on the section where the new Skirball ramps meet Sepulveda Bl. A new third northbound lane will be constructed between the new southbound ramps and the Skirball Bridge.

Construction on the north side of Skirball Bridge and the new southbound on-ramp from Skirball Center Dr has been completed. Demolition works are currently underway on the old southbound on-ramp. The reconstructed bridge will be 30ft wider and include a 10ft-wide travel path.

The northbound off-ramp to Sunset Bl will witness a lengthening of the section by 60%. The Sunset section will involve the construction of two ramps connecting Sunset Bl with the I-405, the north side of Church Ln undercrossing will be widened, and 18,775ft of retaining and sound walls will be constructed.

The demolition of the Mulholland Bridge dubbed as Carmageddon has been completed. The 608ft-long Mulholland Dr Bridge will be 10ft wider when reconstructed.

Contractors involved with the I-405 Sepulveda Pass improvements

Kleinfelder is the lead retaining wall and roadway geotechnical engineer for the project. The application of 4D design approach incorporating 3D computer aided design (CAD) with schedule information for the project is being overseen by HNTB.

“It is currently the largest design-build highway project in Southern California by budget.”

The construction management and inspection services for the project are being provided by CALTROP, while the project controls services including certain requested construction management services for the project are being provided by Kal Krishnan Consulting Services.

The main demolition contractor for the project is Penhall. Two Volvo EC460CHR demolition machines for Mulholland Bridge section of the project were provided by Miller Environmental.