US 34 Big Thompson Canyon Permanent Repair

Colorado’s September 2013 floods remain the costliest natural disaster in the state’s history. The extensive rainfall and duration resulted in flow surges exceeding the 500–year flood event.

The Big Thompson River canyons sustained widespread, massive damage. Major sections of the US 34 roadway were washed away completely, along with access bridges and retaining walls. In the “Narrows” section of the canyon, much of the roadway and grade were undermined, washing out the pavement and embankment from below and exposing the wall tie-back support systems. Numerous residents were isolated and cut-off with no access out of the canyon.

Having experienced similar devastation during a 1976 flood, CDOT wasn’t satisfied with implementing a short-term end solution; rather, they committed to completing emergency, temporary repairs, followed by a flexible and resilient permanent solution – engaging Jacobs as the prime consultant and design lead.

Governor John Hickenlooper reassured Coloradans post-flood that the state would “build back better than before,” which guided the innovative design solutions approach for the design team on the complex project that included 23 miles of high-altitude, winding roadway, in a narrow mountain corridor with no cell service.

As infrastructure is increasingly impacted by natural disasters and agencies are challenged to do more with less – incorporating flexible and innovative solutions is key to more resilient upgrades, and quicker, lower-cost repairs in the event of future devastation. On the US 34 project, we implemented several innovative and resilient solutions such as:

By mixing grout and native material under the roadway to form a solid mass to act as an extension of the existing bedrock, we created a solid foundation for portions of the road to allow a 15-foot drivable surface for emergency ingress and egress. This technique had previously been implemented in building construction, but we found a way to apply this solution to the US 34 roadway to extend resiliency and minimize risk in the future.

Pre-flood, the ‘horseshoe roadway curve’ was on the outside of the river around a tight bend and the forces of the flood water completely washed out the road. Moving the road to the inside of the river and allowing the river to run its natural course on the outside, keeps the road intact during a flood event, maintaining access through the area –representing another investment in resiliency.

The project took a unique approach to traffic control, closing the canyon to through travel during two consecutive winter seasons. These closures helped maintain public safety while enabling crews to maximize the number of roadway and river corridor resiliencies in a short time frame. Optimizing the traffic control allowed CDOT to invest more of their budget in resiliency in the corridor.

With the new resiliency measures incorporated into the project, canyon residents will have, at a minimum, emergency access through the corridor during the next event. The solutions built will have a positive impact on the local economy because for 2.5 months after the 2013 flood, the corridor provided limited or no access to Estes Park, negatively impacting the local and state tourism industry. The resilient solutions will minimize the degree of devastation in the next event, significantly reducing the amount of time and expense it will take to rebuild and restore access to Estes Park – meaning, tourism for the local economy and state will rebound quicker.

The community can now rest easy knowing that our team delivered on the pledge to “build back better than before.”

The US 34 Big Thompson Canyon Permanent Repair project is multi-award winning, being named Engineering News-Record’s 2018 National Best of the Best Project and one of American Council of Engineering Companies of Colorado’s 2019 Excellence Award winners. The project also received the ENR Best of the Best Highway/Bridge award for 2018 and ENR's Mountain States Region recognized it with a Judges Special Recognition and as its 2018 Highway/Bridge Best Project.