Colorado DOT Widens Highway Using Redi-Rock Retaining Walls

THE CHALLENGE

When it snows in Vail, Colorado, it's a skier's dream - but for drivers, especially trucks maneuvering steep mountain roads, it can be treacherous. To make things safer, the Colorado Department of Transportation (CDOT) wanted to widen I-70 at both sides of mountain pass locations to allow trucks to pull off and safely chain-up their wheels.

To widen the road, they needed a retaining wall separating the main road and the adjacent frontage road. However, there wasn't enough space between the two to install a small block retaining wall due to the required length of geogrid.

Aesthetics were also very important to the scenic town of Vail. Specifically, they did not want the light poles set in front of, or behind the wall, so they had to find a way to make them a part of the wall.

"A unique design challenge was integrating the long arm light pole columns with the wall alignment in limited space," noted Sean Chiang, Ph.D., P.E. of Ground Engineering Consultants. "The wall had to be interrupted at every light pole base."

Finally, it was critical to complete the project before the winter ski season.

THE SOLUTION

HDR, Inc. was the overall design engineer of the project. They were able to come up with a design using Redi-Rock that was able to support heavy loads and incorporate the light pole bases into the wall.

Chiang explained the solution like this: "The retaining wall was required to support heavy truck loads, resist potential guardrail impact, and accommodate pavement sections and a curb/gutter behind the wall," he said. "The Redi-Rock PC System with freestanding blocks at the top course was the best option for all these requirements."

The Redi-Rock PC System for Mechanically Stabilized Earth (MSE) walls combines strength and beauty, making it the perfect solution for this project. The geogrid reinforcement strips wrap through each block, eliminating the chance of connection failures.

"The Redi-Rock Positive Connection (PC) was chosen because the system doesn't require long lengths of grid due to the weight of the blocks. That allowed it to fit within the area between I-70 and the frontage road," explained Seth Clark, Business Development/Partner of local Redi-Rock manufacturer Signature Stone. "The PC System also met the stringent Load and Resistance Factor Design (LRFD) and American Association of State Highway and Transportation Officials (AASHTO) requirements."

A custom tie-back system was created so the light pole bases could be integrated right into the wall.

In order to set the poles in line with the wall, hidden from view, seven-foot panel forms were custom designed and fabricated at Redi-Rock headquarters with Ledgestone facing and a special anchorage system. Aesthetically, these panels act as columns protruding forward at each light location.

Because each Redi-Rock block has close to six square feet of surface area, it allowed the contractor to install a large amount of block each day, completing the project ahead of time. The aesthetics also played a big role in this project's success.

"On a high profile job like this, Redi-Rock Ledgestone is the obvious choice," said the installer of the walls, Samuel Carter who is the Project Manager at Miller Wall Company. "The Redi-Rock system allows for the high quality aesthetics that suit the area, with superior design capabilities and ease of construction."

12 inch (305 millimeter) strips of geogrid were used to help tie back the wall.

THE OUTCOME

In total, the project included 16,000 square feet (1486 square meters) of Redi-Rock PC System in the Ledgestone texture, up to 15 feet (4.5 meters) in height. The project also included coordinating Redi-Rock freestanding blocks and caps, as well as some custom pieces to allow the light pole to appear as part of the wall.

"At Signature Stone, we are very proud of this project," Clark added. "The contractor, Miller Wall Company, did a fantastic job installing the wall. CDOT and Vail are also happy with the outcome. The custom panel solution for the light piers, coupled with the custom Ledgestone face and color make this project unique and beautiful."

This CDOT project fit seamlessly with the natural surroundings, and provided a safe pull-off area on the highway.

PROJECT DETAILS

Project: Vail Chain-Up Station #187 Manufacturer: Signature Stone General Contractor: SEMA Construction Installer: Miller Wall Company Design Engineer: HDR, Inc. Engineer: Ground Engineering Consultants Location: Vail, Colorado Year Built: 2016