The historic Mammoth Hot Springs Hotel in Yellowstone National Park will reopen for the winter season after being shuttered all summer.
The facility had to close after the North Entrance road was washed out by the Gardner River during high water in mid-June. Buried alongside the road was a sewer line that carried wastewater from Mammoth to the nearby Gardiner sewage treatment plant. Thousands of gallons of raw sewage flowed into the Gardner River for about a day-and-a-half when the pipe was ruptured.
Park crews eventually rerouted the wastewater into old percolator ponds used from the 1930s to 1960s, enabling Mammoth residents and workers to stay throughout the summer.
“It’s probably the first time you’ll hear me say I’m glad there was some 1960s infrastructure still around,” park Superintendent Cam Sholly noted.
ClosedHowever, it was decided that adding additional strain on the aged sewage system with hotel guests and workers wouldn’t be wise until upgrades were installed.
“This summer we weren’t sure what was going to work and what wasn’t,” Sholly said. “We decided not to take a chance not knowing what that capacity was initially,” so concession employees were moved to facilities elsewhere in the park as Mammoth Hotel was closed.
In addition, travel to the small community of Mammoth, the park’s headquarters, was immediately curtailed after the road from Gardiner was washed out. An 1800s stagecoach two track, the narrow and unpaved Old Gardiner Road, was the only available route.
On Nov. 1, a newly built, $25 million road from Gardiner to Mammoth, following close to the old stagecoach route, is scheduled to open. It travels a different route than the old entrance road — over the hill separating the communities rather than along the Gardner River. Road repairs were also needed to reopen the park’s Northeast Entrance following similar flood damage. That gate was reopened to the public on Oct. 15.
“So much focus has been on the roads, and the road repairs, and reopening the park in different iterations that I think a lot of folks lose sight of how critical and important wastewater and water systems are to, not only hosting visitation, but also from the perspective of the employees and the teams that live in the park,” Sholly said. “You’ve got to have those basic services available…in order to run this park effectively.”
With the hotel staff and guests gone, Jason Murphy, facility manager for all of the park’s water and wastewater systems, estimated wastewater at Mammoth dropped to about 75,000 to 100,000 gallons a day at the height of summer, which by then included day-use visitors.
The older system worked fine in the summer, but it isn’t built for winter, since it is a passive outdoor settling pond that would freeze in the cold. To replace the ponds as a temporary solution, the park has spent about $12 million to have membrane bioreactors installed to treat wastewater. The technology combines biological treatment with filtration.
The new system is being pre-manufactured and will be housed in three buildings with the sludge going to the landfill. Delivery of the bioreactors is expected in about two weeks. The system is large enough to handle the 150,000 gallons per day in the winter with the hotel in operation with a full staff, as well as the roughly 350,000 gallons of wastewater a day capacity needed in the summer, Murphy said.
“We feel pretty confident about that,” Sholly agreed.
Shortly after the June 13 flood broke the sewage line, Sholly said the Park Service was looking into building a permanent facility rather than piping sewage to Gardiner. That seems to have changed, with Sholly now saying the goal is to use the temporary system until a new line, and likely some pumps to lift the sewage over the hill to Gardiner, are built.
Piping wastewater to Gardiner is going to be expensive, Sholly said. Park officials are building a package for consideration, but that will also be dictated by a permanent decision on the North Entrance road since the new sewer line would be buried alongside the route.
Both projects will have to undergo environmental review and a “value analysis,” along with a decision on a permanent North Entrance road, to determine what’s “constructible” based on five main criteria and other sub-criteria, Sholly said. These could include things like: what is the least visually and environmentally impactful, the most cost effective and most resilient to future events.
Sholly said more than $20 million has already been invested in constructing the Old Gardiner Road as a temporary North Entrance route, and that the Park Service would not be “going back on that.” However, the two-lane could be improved with widening, the straightening of some curves and lessening of grades to meet environmental specifications. If an entirely new two-lane road is built, that would take another two to three years of environmental review and “multiple years” of construction, Sholly added.
Once a wastewater pipeline is constructed from Mammoth to Gardiner, the bioreactors could be moved to another location in the park, Murphy said. There are about eight wastewater systems in Yellowstone.
This isn’t the first issue the Park Service has had with its wastewater system. In 2016 the park was sued by the Gardiner-Park County Water and Sewer District over excessive levels of arsenic coming from Mammoth. The suit was settled in 2020 with the park agreeing to pay $1 million to the district. The problem has since been corrected, Sholly said.
Mammoth Hot Springs Hotel, built in 1936, was extensively renovated in a $30 million project completed in 2019. It is one of two operational motels inside Yellowstone in the winter. The other, Old Faithful Snow Lodge, is only accessible by snowmobile or snowcoach. Both serve as jumping off points for other winter park tours that include cross-country skiing, wildlife watching, geyser tours and snowmobiling or snowcoach tours.