Fifty miles east of Los Angeles, Colton Crossing created a bottleneck that dated back to 1883. HDR partnered with more than 20 stakeholder groups to design an 8,150-foot flyover structure to take Union Pacific Railroad's east/west tracks 35 feet above the north/south tracks of BNSF Railway, relieving this chokepoint for the industry. In addition to providing economic benefits nationwide due to increased freight mobility from nearby ports of Long Beach and Los Angeles, this pioneering project has improved life for the local community by easing congestion, improving air quality and reducing noise.

Our team initially provided conceptual design, which helped the community and Union Pacific Railroad obtain grant funding and later provided final design and project management services for Union Pacific Railroad.

Navigating a web of project complexities, we addressed the concerns of many community stakeholders, two Class I railroad companies in addition to other affected business owners. After years of inaction, we developed an innovative solution that resulted in overwhelming support and helped secure public and private funding for final design and construction.

Primary design challenges included keeping mainlines open during construction and overcoming tight site constraints with poor soil conditions and seismic considerations. One answer came from the use of cellular concrete for the support structure, a first for this type of application.

Its resiliency characteristics coupled with a simplified construction process compared to using soil proved this to be a time- and cost-saving innovation. In addition, our custom solution eliminated the need to replace the low-quality soil with several thousand truckloads of imported fill material and reduced the size and number of pieces of equipment required for construction. Today, in place of large retaining walls, there are decorative walls that reflect the community of Colton, providing a harmonious connection between freight rail infrastructure and the surrounding community.

Prior to construction, residents repeatedly complained about noise at the busy rail interchange during multiple pre-project community-impact meetings. Immediately upon opening, the flyover design reduced the need for horn blasts by 50 percent and even greater noise reduction is expected in the future.

Delivered under budget and ahead of schedule, the Colton Crossing Flyover has improved throughput for trains for the two largest U.S. freight railroads, contributing to greatly enhanced air quality. The cause is two-fold. First, it has cut the need for trains to stop and idle. Second, it has drastically decreased traffic backups at nearby grade crossings. Mobile source air toxin emissions have been reduced by 76.7 percent. Furthermore, long-term emissions are anticipated to be reduced by 265 percent by the year 2035.