After a catastrophic 2022 flood destroyed highway sections in Yellowstone National Park, park authorities acted fast to make the repairs necessary to reopen. Because the former North Entrance Road between Gardiner, Montana, and Mammoth Hot Springs was eaten away by floodwaters and unpassable, the work included constructing a temporary highway to connect the towns.
Though that temporary highway has provided year-round access since the disaster, the project was not engineered for longevity.
“It’s done a fantastic job of keeping the park connected to the second-busiest entrance in the park,” Yellowstone National Park Superintendent Cam Sholly said Wednesday during a meeting. “But it does not have the same type of engineering, it doesn’t have the same type of life cycle that you would see with a modern-day road.”
The National Park Service recently released an environmental assessment on plans to rebuild a new permanent North Entrance Road. It’s available for public review and comment through Feb. 4.
The agency’s “preferred alternative” would entail creating a highway route that utilizes some segments of the pre-flood North Entrance Road but mainly stays out of Gardner Canyon, where major flooding damage occurred. It would construct roughly two and a half miles of new road, including several bridges. In addition, it would add 134 parking spaces and 19 turnouts over the 5-mile length of the road.
“Overall, the [preferred alternative] will provide a better driving experience than the current route and provide greater resiliency compared to the pre-flood road alignment,” an informational park service video stated.
The changes will impact major veins of traffic in a park that receives upwards of 4 million visits annually.
Long-term solution
The June 2022 floodwaters wiped out bridges, inundated campgrounds and pulled entire portions of highway into the river. The North Entrance Road, one of only two routes offering year-round vehicle access, was among of the hardest-hit areas.
As a stop-gap solution, federal agencies improved the Old Gardiner Road, a historic, gravel road connecting Mammoth Hot Springs to the North Entrance. Constructed in 1879, the Old Gardiner Road was the original entrance road to Yellowstone until it was replaced in 1884.
The improved Old Gardiner Road had an estimated design life of only five to 10 years, due in part because it’s located on slow-moving geologic slides and poor soils, according to the NPS. Additionally, due to an urgent need to complete construction before the winter of 2022, it was not built to American Association of State Highway and Transportation Officials standards.
In its efforts to find a more lasting North Entrance Road solution, the NPS has worked in cooperation with the Federal Highway Administration to identify four alternative plans for the North Entrance route. They include:
- No action: Maintaining the Old Gardiner Road as is and conducting maintenance, repairs and potential re-engineering as needed.
- The Center Alignment: Creating a new route largely outside of the canyon but also using some reclaimed segments of the old North Entrance Road, and redesigning the Old Gardiner Road as a multi-use trail. This is the agency’s “preferred alternative.”
- The OGR Alignment: Reengineering the Old Gardiner Road to current NPS Park road standards with wider lanes and shoulders, and reclaiming sections of the old North Entrance Road canyon alignment.
- The Gardner Canyon Alignment: Rebuilding the flood-damaged old North Entrance Road in its previous canyon alignment and redesigning the Old Gardiner Road as a multi-use trail.
Risk, resiliency
“Lots of folks have said, ‘Hey, just keep the road that you built in 2022 the same,’” Sholly said. But because that road wasn’t built for longevity, “no action here is not going to be an option for the long term.”
The agency is leaning toward the preferred plan, he said, “primarily because building back in the canyon’s got a lot of risk.”
Even though Sholly is confident the agency could rebuild infrastructure designed to endure future floods in the canyon, he said, the significant rockfall potential in the corridor makes it an unappealing option.
Center Alignment, the NPS-preferred alternative, “represents the best balance between resiliency and project cost by avoiding the Gardner River Canyon as much as possible, thus staying out of the floodplain while maintaining the [Old Gardiner Road] alignment for recreational and emergency vehicle use,” the NPS project page reads.
In the wake of the floods, there have been many discussions about how the park can prepare for the kind of large and unusual climate events that are becoming more common — like the June 2022 rain-on-snow event that precipitated such quickly rising waters. The road project assessment and planning process included evaluations of climate change and evolving hazards within the road corridor, according to the NPS, and climate models helped inform the development of the alternatives.
The bottom line, Sholly said, is that there’s no perfect solution. “This is a very, very important project. We’ve taken time to really do our best to analyze every factor possible, because we want to get this right.”
The NPS will review all comments received during the 30-day public review period and make changes to the environmental assessment or the alternatives if warranted. A final decision will be issued in the spring or summer, according to the agency.