This $632M design-build project increased traffic capacity on the severely congested SR 91 corridor, which carries 280,000 vehicles per day. This was accomplished by extending the existing Orange County Transportation Authority (OCTA) SR 91 Express Lanes eight miles east to I-15 and widening the existing interstate from five to eight lanes in each direction—which included expanding the single HOV lane to two Express Toll Lanes, adding one general purpose lane, and adding an auxiliary lane to manage off/on traffic. The project also included improvements to the I-15/SR 91 interchange, three miles of improvements on I-15, and a tolled express lane direct connector from eastbound SR 91 to southbound I-15. 

The scope of work included 32 bridges and 100 retaining walls—totaling nearly one million square feet (MSE, Soil Nail). The project also included 200,000 cubic yards of PCCP Paving and 290,000 square feet of sound walls.

During procurement, Atkinson/Walsh—a joint venture—presented two Alternate Technical Concepts (ATCs) to deliver a complete and thoughtful technical solution to Riverside County Transportation Commission and, ultimately, Caltrans. These ATCs included: 

1) Revised Express Lane Connectors between SR 91 and I-15: We developed a simplified solution to connect the Express Lanes between SR 91 and I-15 south that reduced the bridge by over 200,000 square feet and the number of straddle bents over SR 91 from nine to two. We also lowered the future SR 91 to I-15 north express lane direct connector ramp by 45 feet.

2) Reduced Lane Widths for Temporary Traffic Control Conditions: We simplified project staging and maintenance of traffic by revising the roadway cross-section for mainline SR 91 traffic. This allowed for 24 feet of outside widening in both directions prior to right-of-way acquisition. It also eliminated the temporary structural section widening and solved sequencing and scheduling issues—limiting the impact of staged construction on drivers.