Rapid growth in the Colorado Rocky Mountain foothills southwest of Denver brought increasing traffic congestion on winding U.S. 285 in the 1970s, prompting concerned residents to begin discussions about improvements with the Colorado Department of Highways as early as 1978.
It would be 13 years before the first improvement project got under way. But once the corridor program started in 1991, it had only a two-year hiatus due to funding issues until its completion on June 19, 2003.
The beautiful 11.6-mile stretch from Parmalee Gulch above Morrison to Log Trail Road near Conifer was rebuilt in five phases, transforming the old two- and three-lane asphalt road into a four-lane divided concrete highway.
Each phase had its own special challenges, rewards and stories that bring smiles to the faces of the three Colorado Department of Transportation (CDOT) engineers who oversaw them.
Blasting their way in
“Phase I was our education in blasting,” said project engineer Jim Zufall, now a CDOT resident engineer at Boulder. “At one point, our blasting subcontractor blew a 12-in. rock all the way over a ridge onto the roof of a home in Parmalee Gulch. After that, we learned a lot about keeping rocks off the road and away from private property, and we learned a lot of lessons about traffic control, too.”
More than 500,000 cu yd of material were moved in the process. The accident-prone at-grade Parmalee Gulch Road intersection was replaced by a 230-ft steel-girder flyover bridge, which at the time of its construction had the tightest curve radius (275 ft) of any steel-girder bridge in Colorado.
The flyover was built with 5-ft-high steel girders fabricated in two pieces, then assembled in place during overnight highway closures.
In the narrow canyon, the merge from the flyover onto mainline northbound U.S. 285 required approximately 1,800 linear ft of cast-in-place retaining walls varying in height from 6 to 26 ft.
Phase II included removal of about 750,000 cu yd of earth and rock. At North Turkey Creek Road, a hazardous and congested at-grade intersection was replaced with separated grades, the first of several such improvements along the corridor.
A typical example of CDOT’s willingness to work with local communities occurred in the Summer Road area where residents were concerned about traffic noise that would follow the Phase II improvements. Zufall, who also was the project engineer for Phases II and III, modified the plans during construction to meet their needs. “We mitigated the noise problem with landscaped earth berms,” he said. “We were all pleased with that result.”
No straight answers
The entire 11.6 miles of the corridor were reconstructed in 10-in. concrete. “That’s unusual for this type of mountain road,” noted Dennis Largent, assistant project engineer for Phases I and II and project engineer for Phase V. “The road was paved full-width in concrete. The first two phases used dowel basket assemblies, but on later phases the paving machine had dowel-bar inserters.”
Although today’s motorists may hardly notice, the first three miles (Phases I and II) of the corridor consist “of almost constant curves. There are almost no tangents [straightaways]. It’s very unusual to do concrete paving in those types of situations,” Largent explained, adding that asphalt is the typical paving material on most curving mountain roadways. Early challenges that occurred in the concrete paving were successfully overcome.
One of Zufall’s favorite memories came from Phase III. “Our office was in a trailer at Elk Meadow,” he said. “Several times I had my first cup of coffee in the morning watching bull elk sparring for control of a harem of 60 to 70 cows.” Built in an area where the canyon finally gave way to more open terrain, Phase III won a CDOT Environmental Award and was noted for its landscaping and rounding of slopes.
“Homeowners at Andrea Lane had concerns about the project, and with their input we changed our design to include mechanically stabilized earth (MSE) walls in order to protect nearby wetlands,” Zufall said. Once again, the result was well accepted.
A Windy wall
Phase IV is best known for its namesake landmark, the prominent southeast-facing Windy Point, where the highway dropped down a steep, sharp eastbound curve and gave motorists their first good view of the Denver metropolitan area far below. Here the road was straightened and widened thanks to months of blasting back the point’s huge rock wall.
“That phase had the most earthwork and the most blasting close to the highway and residences,” noted project engineer John Crowder. “The cut is 190 ft high, one of the tallest in Colorado, and it involved six tiers of tie-back retaining walls. We chose that option after looking at several other alternatives, including a proposed tunnel.”
Considerable fill material from Phases II through IV was used to support the new highway at Windy Point.
“The wall at Windy Point was a design-build feature, and we pushed hard to accelerate the work,” Crowder said. “With our three blasting locations daily, traffic control was a big issue.”
Crowder smiled as he recalled a nearby power line that survived constant blasting for almost a year. “Then, at the very end when we were clearing out dead trees, of course one of them came down the wrong way and cut that line,” he said.
Anticipated— and dreaded
Phase V, which brought the corridor project to completion, could have been nicknamed “congestion reduction.” It also may have been the most eagerly anticipated—and dreaded—of all the phases for residents and through-motorists tormented by frustrating traffic backups at three signalized intersections in the area.
“Residents wanted that section fixed, but understandably they were fearful about what would happen to traffic while we were under construction,” Largent said.
Phase V featured construction of three underpasses and one overpass to eliminate additional troublesome at-grade intersections.
To the surprise of nearly everyone, traffic backups never developed into a major problem during construction. Early on, project officials added auxiliary right-turn lanes and adjusted stoplight timing; both tactics proved effective in limiting backups. Once the intersection grade separations had been completed and the stoplights were removed, traffic flowed smoothly through the construction zone despite ongoing work in the area.
“We got the final phase open 10 months ahead of schedule,” said Largent.
Local officials were so pleased, in fact, that Largent received the unusual honor of being selected Grand Marshal of the Conifer/Aspen Park Christmas Parade. “I got to ride in a Cadillac with my family. We tossed out candy and CDOT trinkets to the kids,” he said.
The final phase of the corridor also required a large amount of work with retaining walls. Among the unique features are a cast-in-place wall to protect an old cemetery at Foxton Road, and, because of its proximity to an electrical substation, a 400-ft cast-in-place wall at Wolf Road in Aspen Park.
Today’s travelers will notice numerous rock faces and what appear to be masonry walls along the corridor. Many of them are, in fact, painted on smooth concrete walls by artists under contract for the project.
“We know that area is the first mountain scenery experience for many westbound motorists coming up out of Denver, so we wanted the improvements to blend in with the environment as much as possible,” Largent said.
Beauty appreciation
Many area residents and frequent corridor motorists are especially grateful that their memories of long traffic backups—caused by the difficult combination of dramatic area growth, proximity to the booming Denver area to the east and traffic signals—can now fade away.
Today’s drivers glide easily along the smooth concrete of the corridor, scarcely noticing the old places where backups occurred. Their memories of following slow-moving trucks for miles without being able to pass are fading, too. The new four-lane highway with its wide shoulders and gentle grades is such an improvement that driving it is a pleasure.
Instead, they are now able to notice some of the major corridor features—frequent wildlife, beautiful mountain scenery, dramatic cuts and graceful new bridges and walls. And, if they gave the matter much thought, they would no doubt be grateful for the enhanced safety of the new highway.
All three CDOT engineers agree that the 12 years of construction went by quickly.
“Traffic volumes tripled from about 10,000 a day when the program began in 1991 to nearly 30,000 a day when it was done in 2003,” Crowder said. “We watched that area of the foothills grow at an amazing rate. I know we were all glad to be able to play a role in helping improve that corridor.”
