SR 4/SR 160 Freeway to Freeway Interchange, Contra Costa County
The Project
The SR 4 Bypass project is a 14.5 mile long segment of new freeway and conventional highway through eastern Contra Costa County and the cities of Antioch, Oakley and Brentwood that is 100% locally funded through fees on new construction. MTCo was the prime consultant for Segment 1 of the Bypass which consisted of 3.1 miles of new freeway, the SR 4/SR 160 freeway to freeway interchange and two local road interchanges, 1.5 miles of local arterial roadway, a 20-acre detention basin and 0.5 miles of flood control channel at a total project cost of $120 Million.
This freeway to freeway interchange project is the most northerly component of Segment 1 and is considered the gateway to the SR 4 Bypass corridor, shifting the intersection of SR 4 and SR 160 1.5 miles south to this location. This interchange was constructed with two separate construction projects the first for construction of the eastbound bridge, the second to construct the Bypass freeway underneath.
The Challenges
The environmental clearance was finalized several years before the start of final design and the SR 4 Bypass Authority Board wanted to accelerate project delivery. Significant residential and commercial activity had commenced adjacent to the proposed Bypass alignment. A major design challenge was to expedite construction of the Bypass while remaining flexible enough to accommodate adjacent development projects being planned under equally aggressive schedules.
This freeway to freeway interchange was located between three cities with different desires on connections, and project components all of which required Caltrans concurrence.
The Results
Working with the SR 4 Bypass Authority staff, a project (SR 4/SR 160 Interchange) was identified that could be designed and constructed a year ahead of starting the main Bypass Segment 1 package. MTCo worked on both projects concurrently and completed the design of both projects within a 2½ year period.
Today the SR 4 Bypass is held up as a model of interagency partnership for accelerated project delivery.