Fast-track emergency repair of the Beartooth Highway, Red Lodge, Montana

William Perkins, L.E.G.
Senior Principal Engineering Geologist
Shannon & Wilson, Inc.
Seattle, Washington

Built in the 1930s, the scenic Beartooth Highway (U.S. Highway 212) is heavily traveled by tourists visiting Yellowstone National Park by way of the rugged Beartooth Mountains and the high mountain communities of Top of the World and Cooke City. While clearing snow from the highway to prepare for the 2005 seasonal spring opening, a severe and untimely rain-on-snow event triggered two massive debris flows that damaged or obliterated the roadway at 13 locations. Using a hybrid design-build approach, a 2-1/2-year design-bid-build project was compressed into four months, meeting the project goal of restoring the road and opening the route before the 2005 seasonal fall closure.

The highway crosses the Beartooth Mountains on the Montana-Wyoming border and is a principal access to the northeast entrance of Yellowstone National Park. As it crosses the mountains, the narrow two-lane roadway rises vertically over 5,000 feet in a series of switchbacks to the 11,000-foot summit. Winter snow at these elevations closes the highway between mid-October and May.

On May 19 and 20, 2005, as snow removal operations were underway, runoff from an intense rain-on-snow event was concentrated in the partially cleared roadway, which acted as temporary channel formed by the cut snow banks on the sides of the roadway. At two locations where the snow banks were unable to contain the concentrated runoff, it flowed down the mountainside and triggered debris flows and formed chutes that moved nearly 100,000 cubic yards of soil and rock down the mountain and across the roadway. Because the roadway switchbacks up the mountainside, the two debris chutes crossed the roadway at multiple locations, damaging the road in 13 places over a 10-mile stretch. The highway had to be closed as a result of the severe damage. The erosive force of the debris flows often left gaping holes in the roadway with guardrails and culverts shredded and dangling in mid-air.

A traditional design-bid-build approach to repair and reopen the highway would require about 2-1/2 years. With the highway closed and access to Yellowstone National Park restricted, it was feared that the economies of local communities dependent on tourism from Yellowstone would be severely impacted. Consequently, with an emergency declaration by Montana's Governor and a U.S. Congressional mandate to provide "unfettered access to Yellowstone National Park and preserving the economy," the Montana Department of Transportation (MDT) resolved to repair and reopen the roadway by October 15, 2005 using a hybrid design-build (D/B) fast-track approach. This approach combined a force account payment method with large incentives for early completion and large disincentives for late completion. This contracting method achieved the desired result of early completion (two weeks ahead of schedule) and within budget (approximately 30% below the $20 million cost estimate and budget).

The difficult site conditions led to some concern whether or not the project could be completed by the end of the upcoming construction season as required by the project contract. Because of these concerns, only one D/B team responded to MDT's Request for Proposal. However, on June 15, the project was awarded to the D/B team led by the General Contractor, Kiewit Western Co. of Littleton, CO, and included JTL Group of Billings, MT (construction), HKM Engineering of Billings, MT (design management and civil engineering), Shannon & Wilson, Inc. of Seattle, WA (geotechnical/geologic engineering) and Womack & Associates of Billings, MT (geotechnical/geologic engineering).

In addition to the physical constraints and conditions of the sites, roadway restoration design and construction also had to consider the demanding schedule, the availability of material and equipment to maintain the schedule, and the need to keep construction access open to all repair sites so that construction could occur simultaneously at multiple sites. The construction access requirement was particularly critical given the remote location and the fact that site access could only be gained by using the steep, winding highway itself.

With these additional schedule and access constraints, design and construction to restore the roadway prism included:

  • debris removal,
  • two mechanically stabilized earth (MSE) walls with truncated reinforcement,
  • micropile and rock dowel stabilization of MSE wall foundations,
  • temporary soil nail shoring without shotcrete facing at one MSE wall site to maintain construction access,
  • seven engineered rock fills, and
  • approximately 1/2 mile of rock blasting and roadway realignment.

To prevent a repeat of the runoff concentration that triggered the debris flows, dual runoff drainage/debris handling systems were designed and constructed. However, the over-steepened sides of the debris chutes themselves pose a debris flow hazard even without the runoff concentration. Probabilistic and deterministic debris flow hazard models were developed, and analyses were performed to determine the likely volumes and recurrence of future debris flows from the eroded chutes. Based on the volume and recurrence estimates, a hazard reduction matrix was developed to assist MDT in selecting debris flow hazard mitigation measures. The measures selected by MDT, designed, and constructed included:

  • three debris flow fences (one of which is the tallest of its kind in North America),
  • one rock-fall drape, and
  • two debris flow training berms.

In addition to restoring the roadway prism and mitigating future debris flow hazards, the project also required removal of several thousand cubic yards of debris flow material to restore creek drainage that had been buried by up to 40 feet of debris. Instead of wasting the debris, much of it was processed onsite and was used in the engineered rock fills. The reuse of this material reduced the time that would have been used in transporting additional material to and from the site and overall costs.

Close cooperation between the MDT, the D/B team, and other stakeholders including the National Park Service, Federal Highway Administration, Forest Service, U.S. Army Corps of Engineers, and the Montana Department of Environmental Quality was crucial in completing the project within the allotted construction window. Other keys to meeting the project's schedule requirements included a mutual understanding between MDT and the D/B team of the D/B processes and relationships, co-location of contractors and designers, frequent coordination between the owner and the D/B team, and an expedited design/plan review process.

William Perkins is a licensed engineering geologist with Shannon & Wilson, Inc. and was the Geotechnical/Geologic Design Manager for this project. He can be reached at (206) 695-6879 or wjp@shanwil.com.

The Beartooth Highway Emergency Repairs project is one of the 2006 APWA Projects of the Year. Descriptions of all nineteen Projects of the Year will be included in the upcoming July issue of the APWA Reporter.