OCEA Project Finalist – Colton Crossing Flyover

September 3, 2014

This is the first of a series about the five finalists for ASCE’s Outstanding Civil Engineering Achievement (OCEA) awards. Established in 1960, the OCEA Award recognizes a project that makes a significant contribution to both the civil engineering profession and society as a whole. The winner of this year’s OCEA award will be announced at ASCE’s Outstanding Projects And Leaders (OPAL) Gala, March 26, at the Renaissance Arlington Capital View Hotel in Arlington, Virginia. Today, read about the Colton Crossing Flyover.


Photo Credit: Keith Philpott Photography


Dubbed the “oldest bottleneck in U.S. history” by the U.S. Department of Transportation, Colton Crossing  was built in 1883 as an “at grade” rail-to-rail intersection situated in Colton, California, about 50 miles east of Los Angeles. With an average of 125 crossings daily, it is one of the busiest and most congested railroad crossings in the U.S. Engineering firm HDR designed an innovative approach to eliminating the chokepoint by constructing an 8,150-foot flyover structure to take the Union Pacific Railroad’s east-west tracks 35 feet above the north-south tracks of the BNSF Railway (the 2 largest freight railroad networks in the U.S.). Passenger rail lines also use these tracks.

However, a multitude of engineering challenges accompanied the project, beginning with the site’s severe space and right-of-way constraints, which did not allow for side-sloped embankments for the approach of the bridge. The HDR engineers estimated that 39-foot-high retaining walls would make up 40% of the estimated $202 million project cost and also require replacement of poor soil.

Instead, the project team employed an innovative approach by using lightweight cellular concrete fill with precast concrete panel walls for the retaining structure. Although it had never been used in this quantity or at this height, cellular concrete offered the exact properties needed: its self-supporting nature meant there was no need for conventional retaining structures; and the material’s light weight also reduced the amount and size of equipment needed to construct the approaches, allowing rail service to go on during construction. All told, use of the material saved more than $30 million, helping to deliver the project more than $100 million under budget, and expedited delivery by 8 months.

The OCEA jurors wrote that the Colton Crossing Flyover is “an excellent example of creativity/resourcefulness in using cellular and precast concrete for retaining structure. [It is a] well-documented project showing connection to multi-modes of commerce and transportation. It is a complex project that eliminated a persistent bottleneck in the community. Cellular concrete is lower density than earthen backfill, so its use in this project eliminated the need for conventional structures because of its self-supporting quality.

“This design decision saved the owner [Union Pacific Railroad] $30 million and solved some of the challenge of working on a constrained, tight site. An intricate project designed to remove a flat crossing between north-south BNSF and east-west Union Pacific tracks was achieved under budget to improve the movement of goods and bring down traffic congestion. Such smart-planning projects should be emulated and occur more often.”

Next in the series, read about the Echo Park Lake Rehabilitation Project

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  • Awesome…!!! I wish Discovery /History channel would do a program on this for their “Engineering Marvels” . I would show it on my Live PDH seminars.


    Franco Davati, P.E.

  • Were there any additional seismic design concerns with this particular approach?

  • L.S.,

    In the Netherlands we more go (half)underground, although we have a big problem: high groundwater level everywhere.
    See i.e. Delft Railway high in the air 1963 (like Colton) and now underground … much better. No horizon-pollution, no noise-pollution, no air-pollution, better/easier communication between areas on both sides of the railway, …

    M.J. Vos MScE/CE of the University of Delft

  • My, congratulations on resolving the excessive queuing of traffic on the Colton Crossing Flyover.
    Colton, California. And, the nation’s others cross-over flyovers should be like wise studied.

  • Nice work

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