Yellowstone National Park officials outline permanent North Entrance Road options

BILLINGS – There are three proposals for a new North Entrance road Yellowstone officials have put before the public for consideration: rebuild the old route along the Gardner River that was washed out in the 2022 flood; realign the road near the temporary route now being used before dropping down to the Gardner River; or use the newly built temporary road that descends into Mammoth Hot Springs. All of the roads would be 30 feet wide.

“It’s important we take our time and get it right,” said Cam Sholly, park superintendent, adding it will be a significant investment.

The three alternatives were presented to the public in a Monday afternoon online meeting. A similar gathering was held Wednesday. The three chosen alternatives were narrowed down from a total of six that were originally considered.

Rebuild canyon

Going back to the old canyon route would require the installation of a “longer and higher profile bridge” across the Gardner River. Where the road washed out in June 2022, a “multispan bridge structure is proposed to parallel the river channel, while avoiding the failing east side slope, debris flow chutes and landside toe on the west side,” the Park Service noted.

After that, the road would enter a “rock-shed structure” for about 1,000 feet for protection before the final bridge crossing closest to Gardiner. An existing steel retaining wall after the second river crossing would remain and be reinforced.

“One thing about the canyon … it would have to be built … to be resilient to another flood event,” Sholly said. “I’m confident we could do that. We have to look at some other factors. It would probably be pretty expensive.”

Temporary road

Alternative 2 would use the Old Gardiner Road, which is the newer temporary road built after the flood, but widen the surface from 22 to 30 feet. The widening would require some of the existing retaining walls and drainage to be replaced or enlarged. Some of the tighter curves would be widened to improve safety and the grade would be lessened on some hills. The alignment of the road to the entrance would be reconfigured.

This alternative has the drawback of requiring “pretty significant traffic disruptions” while the work is done, which could run for three to five years, Sholly said.

If another route is chosen, this road could remain as a service road or bike path.

“I don’t know that it’s worth spending … $15 million plus to undo what we did in 2022, and turn it back into a one-lane dirt road,” Sholly said. “I think there’s some value in having some redundancy.”

Down the middle

The third alternative is to follow the North Entrance road for 2 miles north out of Mammoth Hot Springs. At the first crossing of the Gardner River, which is at the parking area for the trail to the Boiling River, a longer and higher bridge would be built. The road would continue to an area referred to as China Gardens where a new bridge would cross the river and connect to a new road alignment climbing out of the canyon and past the west side of Slide Lake. Near there it would connect with the existing temporary road for almost a half-mile before going back to the preflood North Entrance Road and on to Gardiner.

“The nice thing about this is it stays out of the canyon,” Sholly said. “It takes advantage of the 2 miles or so of road from Mammoth down to the Gardiner River. We would improve that as well. This could be executed as a completely separate contract that would not affect visitors coming in.”

This route has engineers concerned about soil stability, which they encountered when building the temporary road. Instability can be addressed, according to Nate Jones, of the Federal Highway Administration, by not making big cuts or fills and using lightweight soils as fill.

“The soils are relatively unstable,” Sholly said. “They’re shifting. That shift can be pretty substantial, depending on where you want to build a road.”

All of the proposals have the problem of impacting archaeological sites, 34 of which were identified between Mammoth and Gardiner, according to Tom James, park archaeologist. Of the three alternatives, the Old Gardiner Road would impact six sites, four in the canyon and as many as 14 in the center alignment.

One of the main goals of the new entrance road is to make it resilient to climate change, something that Bob Kammel, chief of professional services in the park, has been studying with the design team.

“We are looking at the frequency and intensity of storms as they relate to the corridor and what that means in terms of these three alignments,” Kammel said. “We’re very focused on landslides, rockslides, rock fall and some of the relationships of those kind of natural occurring events with the infrastructure that’s proposed.”

Other issues

The chosen route will also be where the Park Service buries its new sewer service line to connect to Gardiner’s wastewater treatment plant. The former line was washed out in the flood, forcing the Park Service to use an old wastewater system until a new temporary facility could be installed.

If the route through the canyon is not rebuilt, Sholly said the remaining asphalt would be removed.

“Personally, I think restoring that canyon to its natural state would be good,” Sholly said. “I do think probably of the three it’s the most expensive and the most vulnerable to future events, floods, rock slides, whatever the case may be.”

In other work along the flood corridor, the Boiling River parking and picnic area will be retained. The Mammoth campground should reopen to the public this season once a new sewer line is connected to the temporary wastewater treatment site. A location for the Rescue Creek Trail bridge has been identified, and a new bridge should be installed by this fall or next summer.

Second busiest

The North Entrance is the second busiest in the park with up to 3,000 visitors a day during peak summer visitation. It is also the only route in the park open to automobiles year-round. Drivers can continue from Mammoth past Tower Junction and the Lamar Valley on their way to the northeast corner of the park and the Montana communities of Cooke City and Silver Gate.

The park road is the only way to access the two communities in winter. Both are popular for winter recreation, including snowmobiling, Nordic and backcountry skiing and snowboarding.

Highway help

The route proposals were developed by the Park Service in cooperation with the Federal Highway Administration. That’s the same agency that helped engineer the temporary route into Mammoth via what was an old stagecoach road.

The June 13, 2022, flood wiped out vehicle access for most visitors until the temporary road was reopened on Oct. 30 of that year, four months later. In between, the Park Service enabled some outfitters, guides and NPS staff to use the stagecoach road, built in 1879 and replaced in 1884, until the new route was finished at a cost of $25 million.

A decision on a new route will be proposed this summer in an environmental assessment. That document will also be open to public comment.

Right now the public can comment online at parkplanning.nps.gov/NorthEntranceRoad. Comments may also be mailed or hand-delivered to: Yellowstone Center for Resources Attn: North Entrance Road EA, PO Box 168, Yellowstone National Park, Wyo., 82190. The deadline to submit comments is March 13.