On top of the slide

Amy Train / July 15, 2010

Boulders, some as big as tractor-trailers, pummeled I-70 in Glenwood Canyon in early March, leaving the only east-west Rocky Mountain artery closed for four days.

One week after the massive rockslide, Flatiron was selected as the contractor to conduct vital repairs to the damaged roadway about 100 miles west of Denver.

“We were able to react quickly and we have past experience working in Glenwood Canyon,” said Scott Stetson, Flatiron’s general superintendent for the project. “We mobilized and began working right away.”

The aftermath of the destruction resembled a scene straight from Hollywood, with enormous boulders strewn across an area the size of a football field, rebar sticking out of holes as large as a compact car and twisted steel guardrails tossed aside like crumpled paper. Rocks and debris broke loose from canyon walls, punching holes in the roadbed and tearing into retaining walls and bridge girders near the Hanging Lake exit, causing a 17-mile stretch of the highway to be closed to traffic. Because of the rugged terrain, the highway closure required traffic detours; the shortest added about 200 miles to the commute time, sending motorists north of the Flat Tops Wilderness Area.

The Flatiron team knew it was important to complete the work within the 55-day contracted time frame.

“We actually began after CDOT had opened one lane eastbound and one lane westbound,” Stetson said. “We had to finish the cleanup to expose all the damage. CDOT had cleared the travel lanes and moved the debris aside. Flatiron cleared the bike path below the bridge and retaining walls and removed all the boulders.

“Within the first three days we had the jobsite cleared of all big rocks and boulders,” Stetson continued. “When we began, it was a mess. The damage was unbelievable.”

Not the typical type
Following the debris-clearing stage that included moving boulders, one estimated weighing 66 tons, Flatiron’s first order of business was to fix the damaged steel girder. One of the girders in the steel structure required use of a flame-straightening technique. CDOT had originally projected the straightening to take six days. In actuality, it took 11 days, Stetson said. “It was damaged a lot more than first thought,” he said.

After straightening the girder, workers began repairing holes in the bridge deck. This portion was broken down into phases as traffic had to be moved during the process. It took about a week and a half for Flatiron to fix all of the holes, the largest measuring 20 ft by 10 ft. Flatiron completed the repairs and paving the first week of May.

Flatiron subcontractor Rock Solid installed 14,000 sq ft of wire mesh (rock-fall netting) along a section of the canyon wall near the bottom of the two chutes where the rocks fell. CDOT added this safety precaution in part because a 2-ft by 3-ft boulder crashed into a vehicle as it passed through the work zone on March 25. Luckily, the passengers were not injured.

“The wire mesh is designed to keep smaller rocks (less than 3 ft in diameter) that may release from the talus slope above from reaching the highway,” said Ty Ortiz, CDOT geologist. “The goal is to reduce the chances of these smaller rock incidents; the mesh is not intended to mitigate an event like the one that occurred on March 8.”

Flatiron would be eligible for a bonus of 5% of the contract if it completed the work 10 days early and was on track to finish the repairs, striping and wire-mesh mitigation work by May 18 and earn the maximum allowable bonus. Alternatively, if work continued past the time allotment, Flatiron would have been charged a $5,000-per-day penalty.

Flatiron also saw a cost and schedule savings opportunity during the project with the twin-T retaining walls. “We bid to precast the Ts and set them,” Stetson said. “We ended up changing that and cast them in place, saving several days on our schedule.”

Despite the dangerous work area, Flatiron maintained its zero lost-time incidence record, which it has done for more than a year on projects across the U.S. and Canada. To help spot falling rocks, an aptly named rock spotter watched the mountainside and warned crews and flaggers when high rocks dislodged. Generally, there was about 10 seconds to clear the work area and stop traffic before the rocks reached the highway. “We had communication with the tunnel by radio to stop traffic immediately if there were any problems,” Stetson said.

To Stetson, every aspect of the Glenwood Canyon work was interesting. “It was a lot different than other construction jobs because of the magnitude of the damage,” he said. “It’s not a typical fix. Normally we’re building new structures or fixing something that failed due to age.”

While it wasn’t a typical job for Flatiron, the damaged freeway was practically in Flatiron’s backyard. In fact, Flatiron’s district manager, Terry Ostrom, managed his very first job for the company on this stretch of interstate in the 1980s.

Rugged iron
Flatiron received national recognition for the construction of a series of projects in the Glenwood Canyon corridor of I-70 in the mid-1980s to early 1990s. All of these projects were built under conditions of stringent environmental requirements, strict traffic-disruption restrictions, harsh winters and restricted workspace. The Glenwood Canyon Corridor included 12 miles of separated eastbound and westbound lanes. Many of the westbound lanes were constructed using elevated viaducts, while most of the eastbound roadway platform was constructed using precast twin-T retaining walls.

“This spring, nearly 30 years after those first projects, we had another quality, experienced group of Flatiron employees, who spent long hours to finish ahead of schedule. CDOT was very involved, experienced, capable and flexible. The CDOT-Flatiron relationship was essential for the early completion of the repair project.

“The most interesting and challenging elements to me were the quick schedule in this remote and rugged location,” said Jorey Deml, project manager. “We encountered all types of weather during the two months but could not stop and wait for it to pass. Much of the communication going outside of the project had to be done via texting since cell phones did not work.”

Despite scope changes, mainly rock-fall mitigation that increased the scale of Flatiron’s work by 70%, the completed date was 13 days ahead of schedule at press time.

“We would have been faster still if the rock-fall netting was readily available,” Stetson said. “We would have finished at least two weeks sooner if the rock-fall netting was sitting on a shelf somewhere, instead of having to custom order it.

“I think the success of this project is a testament to the team we had on the project,” Stetson continued. “Joe Elsen and Rolland Wagner of CDOT and Jim Shea of HRH did an excellent job planning and were responsive to the quick nature the job demanded. We had excellent subcontractors and a great Flatiron crew.”

About the Author

Train is a communications specialist with Flatiron, Longmont, Colo.

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