The High Road: Paving at 12,000 Feet

Photos courtesy of the Federal Highway Administration, Central Federal Lands Highway Division

Cottonwood Pass in Colorado is the fourth highest paved road in the nation, making this project an engineering feat

By Julia Edinger

In the heart of the Gunnison National Forest, mountains, pine trees, and lakes decorate a scenic Colorado landscape. Up until this project’s completion, Cottonwood Pass was a gravel road wrapping around the sides of mountains. Now, it’s the fourth highest paved road in the United States.

This $20 million project to improve Cottonwood Pass provided more reliable access to Gunnison National Forest in Colorado. The project reached a summit of 12,126 feet, making it the fourth highest paved road in the nation.

“The purpose of the project was to provide a safe and sustainable roadway that improved access to Gunnison National Forest lands while reducing Gunnison County maintenance costs,” explained James Herlyck, Federal Lands Access Program Manager of the Federal Highway Administration’s Central Federal Lands Highway Division (FHWA-CFLHD).

Planning for a Mountain Pass

The project was a complex undertaking with multiple entities involved in bringing it to completion. Improvements to Cottonwood Pass have come in the way of two separate projects addressing rehabilitation on both the east and west side.

The 12.5 mile span of road was improved with pavement, lane adjustments, and drainage improvements.

Not only did this Cottonwood Pass project pave the gravel road, it also adjusted lanes, shoulders, and drainage. Safety improvements were made through a number of features, including horizontal alignment changes, added signage, and striping.

A dedicated team worked on the project, with FHWA-CFLHD leading and United Companies as the builder. The Colorado Department of Transportation does not own or operate Cottonwood Pass, but did contribute Highway Safety Improvement Program funds and helped with public outreach during the project’s construction.

Other key players included the project manager, environmental protection specialist, geotechnical engineer, and lead highway design engineer. When the project was given notice to proceed in the spring of 2017, the original cost estimate was $27 million. Collaboration and innovative design allowed the project to be completed $6.1 million under budget, according to Herlyck.

Building At Great Heights

“The project began at an elevation of 9,363 feet and ended at the summit of 12,126 feet,” Herlyck stated. “During construction, as one might suspect at these altitudes, weather and temperature were constant challenges.”

The extreme altitudes posed several challenges. For example, crews could only work in the highest regions during the months of summer and early fall, as rain and snow were common in the winter months. That weather wasn’t always predictable, though; in June of 2019 there was a summer blizzard.

The weather conditions of the extreme altitudes required teams to limit construction work to summer months.

Subsurface water posed the other major challenge. The team included additional underdrain and sub-excavation to stabilize the roadway while controlling the flow of water.

“In all, 18,390 feet (almost 3.5 miles) of underdrain was installed and 22,830 cubic yards of sub-excavation was done,” Herlyck summarized.

While many aspects of the project were complicated by the height, it is also one of the greatest sources of pride in regards to the project’s success.

Said Herlyck, “This is the fourth-highest paved road in the United States, traverses a pristine natural environment home to many plant and animal species, and oversees a rugged landscape.”

Environmental Matters

This picturesque mountain pass required careful environmental consideration to protect the surrounding lands, including plant and animal habitats.

FHWA-CFLHD completed National Environmental Policy Act compliance, an important measure in regulating large construction projects to protect the environment.

“We value strong Government-to-Government partnerships to successfully deliver projects,” Herlyck stated. The partnership between FHWA- CFLHD and Gunnison County allowed the project to address the key goals the project intended to address in a way that is conscious of the surrounding environment.

The dedicated team at the Federal Highway Administration’s Central Federal Lands Highway Division enabled the project’s success. The project’s successful outcome was made possible through collaboration with the project manager, environmental protection specialist, and the engineers.

The 12.5-mile span of road was adjacent to a number of precious wildlife habitats, including that of the Canada Lynx and a number of wetland ecosystems. The project not only restored over an acre of wetlands onsite, but also purchased several acres of wetlands nearby.

Other measures taken to protect the environment included using onsite material sources to create all of the rock and aggregate needed for the project, which also helped to reduce emissions from transporting materials. The use of rock buttresses, rather than man-made structures, also allowed the project to blend with the natural environment.

“The collaborative team effort identified these areas and the design resulted in the least amount of disturbance possible, while achieving the project purpose and need,” Herlyck said. “We are proud that the public now has improved access to our national treasures through the investment of federal, state, and local resources.”

In total, 18,390 feet of underdrain was installed and 22,830 cubic yards of sub-excavation was done.

Not all road projects are able to take such careful consideration into the environment, but for a project that is so closely tied to precious federal lands, it was crucial that the team took a new approach. Because of the dedication to the project, Cottonwood Pass will provide safe, convenient access to Gunnison National Forest for years to come.

Julia Edinger is the Editor for American Infrastructure Magazine. She can be reached at julia@builder.media.

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