High-Altitude Asphalt Paving

By Carol Carder | September 28, 2010

Tourist traffic, limited turnaround space, mixes to withstand an arctic environment — these are just a few of the challenges to high-altitude asphalt paving projects. This past summer Lafarge North America of Colorado Springs paved portions of the Pikes Peak Toll Road while Kiewit Western of Littleton undertook a paving project on Trail Ridge Road in Rocky Mountain National Park.

Virgin Paving on Pikes Peak

"This year's paving was the toughest," says Scott Kenley, project manager, Lafarge North America. Lafarge paved approximately 2,800 tons or around 3,000 linear feet on the Pikes Peak Toll Road. Next year Lafarge will pave from the Summit House at 14,000 feet elevation down a mile. The challenge was the location just below Devil's Playground between 12,000 feet and 13,000 feet elevation. The switchbacks are so tight in this area, the big rigs couldn't negotiate them to bring the mix to the paver. So Lafarge set up a transfer point at Glenn Cove. There the big rigs dropped the mix, and tandems picked up the mix to take it three miles up the mountain to the paving operation.

General contractor Frontier Environmental Services Inc. of Wheat Ridge prepared the existing gravel road for its first asphalt application by building a subgrade and put in concrete drainage ditches. Ironically, Frontier had to import aggregate from the local ski area to build the subgrade on the dirt base.

"Safety was our top priority," says Clint Stalcup, Lafarge paving superintendent. Precautions included toolbox talks with the workers on the dangers of high-altitude paving. Workers were advised to drink plenty of water to hydrate and oxygenate the blood. Taking a cue from high-altitude hunting, Stalcup advised the workers to start chewing Tums two to three days before the project started so the calcium would prevent altitude sickness. Advance preparation also took into consideration the remote paving site and included contingency plans such as having a mechanic on-site in case anything went wrong.

"This was a wise decision as we had a mechanical breakdown on our laydown machine," adds Nick Olguin, paving foreman. "Negotiating the tight turns caused a track to start coming off the paver, and we got it fixed within an hour's time."

During the paving operation, personnel on-site with heat guns checked the temperature of the truck wheels and brakes to make sure they weren't overheating. "We set the guns to check for temperatures exceeding 300 degrees, deciding the truck would have to sit until it cooled down to 250 degrees," Kenley explains. "We didn't have anyone over the temperature limit the whole job."

The mix is a PG 64-34 and was obtained from SEM Materials in Commerce City. Lafarge installed it in two lifts totaling 4 inches.

"Weather is always a challenge at high altitude, and we were fortunate to have good weather when we paved at the end of June," Kenley observes.

As this was written, Lafarge was busy laying down asphalt in Cripple Creek while the weather holds. The company recently finished the parking lot at the Heritage Center, is currently widening Highway 67 and will be paving Galena Avenue in Cripple Creek.

Reconstruction on Trail Ridge Road

"With a million cars a year traversing Trail Ridge, it's an effort to upgrade our roads to accommodate the traffic and keep up with needed maintenance," says Joe Arnold, Rocky Mountain National Park engineer. In fact, the last asphalt overlay on Trail Ridge Road was placed in 1984.

Trail Ridge Road, which reaches an altitude of 12,183 feet, is the highest continuous paved road in the continental United States. At this elevation, the road is exposed to harsh elements including heavy snowfall, freeze-thaw conditions and strong winds.

This past summer, Kiewit Western of Littleton put down 24,000 tons of Superpave in two phases of the $10.2-million reconstruction. The first phase was a 7.8-mile-long continuous section of Trail Ridge Road between Deer Ridge Junction and Rainbow Curve. The second phase was repair of seven higher-elevation roadway sections totaling 1.5 miles. Here severe freeze-thaw conditions had caused the roadway to buckle over the years. Kiewit first focused on rebuilding the lower elevation section of roadway and then moved to the higher elevation spot repairs in the summer when weather conditions improved.

In the first phase of reconstruction, the contractor milled 3 inches of asphalt, stockpiled it and pulverized the remaining 4 inches of asphalt. The Superpave lift is a PG 58-40 binder from SEM Materials in Commerce City at an optimal 5.3 percent. The aggregate in the mix was blended to meet 12.5-millimeter nominal maximum aggregate size. This is a combination of 47-percent crusher fines, 22-percent half-inch rock, 20-percent washed sand, 10-percent native fines, and 1-percent lime.

"The sheer volume of traffic is a major challenge to construction," Arnold observes. "We cannot do this work when we have 20-foot snow drifts so it has to be accomplished in summer."

From April 1 to May 24, the park closed the lower 7.8-mile section of Trail Ridge on weekdays allowing crews to rebuild this highway section prior to the busy tourist season. After July 4, work moved to weeknights with a 10 p.m. to 6 a.m. window for high-altitude road repair. However, due to low night temperatures near the summit of Trail Ridge, paving took place in daytime hours. For this daytime paving, Kiewit worked under the stipulation of stopping traffic no more than 60 minutes total for all seven work zones.

"Handling traffic was huge, so communication with traffic control personnel was crucial," says Jorey Deml, Kiewit project manager.

Also changing weather conditions and preserving the Trail Ridge environment above timberline were unique factors in the work. Before performing repairs at the seven high-altitude sites, crews relocated the fragile tundra. Also, crews carefully moved historic rock walls dating back to 1926 and 1932, then restored the walls to their original condition after repairs.

The remote location with some sites 20 miles away added scheduling challenges in material deliveries and workforce deployment. Kiewit worked closely with the National Park Service to establish material staging areas that enabled ready access to some materials while minimizing impact on the environment and visitors' enjoyment of the park.

"During the first phase, the belly-dumps bringing the asphalt up from Loveland had only three areas where they could turn around," explains Dennis Black, FHWA project engineer.

New technology, a geocomposite capillary break system, was completed at a badly rutted area 0.7-mile long, directly south of the Alpine Visitors Center, according to Black. The crews dug about a meter below grade then layered the composite fabric between layers of dirt to form a durable subgrade. According to Mark Meng, P.E., with FHWA, this geotextile will wick moisture from the subgrade. This fix was also applied at three other shorter stretches of road.

At another repair site near the Colorado River and the first switchback at Fairview Curve, a leaking pipe had allowed water to undermine the road, forming a sinkhole. Here the contractor performed compaction grouting to repair the base.

Kiewit finished the lower 7.8-mile section seven days ahead of schedule, earning an incentive. As this was written, Kiewit was on schedule to finish ahead of the contract completion date of Sept. 21.