Latest repairs on Mount Sanitas reflect challenge of upkeeping Boulder’s most popular, but poorly designed, trails

Over the course of several hours last Tuesday, trail workers strapped 75 bags of sandstone mined from a quarry on the east side of Mount Sanitas to a helicopter. The stone, weighing 52 tons, was then flown to the nearby Mount Sanitas Trail, one of the city’s most popular hikes located less than a mile from downtown. 

The cost of moving the stone from one side of the mountain to the other was about $34,000, according to city officials. It was paid for by a donation from the Boulder Open Space Conservancy, a nonprofit organization raising money from residents for trail repairs. 

The rock haul was part of an ongoing trail maintenance project on the busy trail, which receives roughly 300 visits per day, according to the city. In 2023, trail crews will use the sandstone to continue repairing retaining walls and building stone steps. 

That such an operation is necessary reflects the challenges Open Space and Mountain Parks faces when trying to upkeep trails that many residents cherish, but that were designed many decades ago, and poorly, according to today’s standards. Mount Sanitas was built in the early 1900s by the Boulder-Colorado Sanitarium, the former health and wellness center after which it was named.

The Mount Sanitas Trail is considered one of the city’s “legacy trails,” meaning they were adopted into the OSMP system and did not meet modern trail design standards. It ascends about 1,300 feet in 1.2 miles, making it particularly susceptible to erosion from fast-flowing runoff and relatively costly and time-consuming to upkeep. Other legacy trails in Boulder include those used to access the Royal Arch and the First and Second Flatiron. 

“These types of trails are iconic. They’ve been part of the fabric for a long time. But they come with more maintenance,” Phillip Yates, a spokesman for Open Space and Mountain Parks, said in an interview. 

For the past several years, the city has been replacing the Sanitas trail’s loose rocks and washed out retaining walls with timber steps and professionally designed stonework. In 2019, OSMP and Mile High Youth Corps trail workers completed several flights of stone steps. On the west side of Sanitas, the Lion’s Lair Trail, with its gradual grade and frequent switchbacks, is an example of how trails are built to shed water without eroding.

The Sanitas project slated for 2023 will likely continue this work. By fortifying the trail, the city seeks to reduce its overall footprint on the surrounding environment. Washed out trails cause people to chart new paths, effectively widening the trail in the process and causing harm to vegetation. 

Some hikers might not want more steps built on Sanitas, which could make the relatively difficult trail easier to ascend. But OSMP is trying to balance those desires with ecosystem preservation. 

“It’s about trail design and how we work together with our biologists and our ecologists to help maintain good visitor experience while also protecting the natural resources,” Yates said. “We have to think about both.” 

All told, the city’s 150 miles of designated trails receive 5.5 million visits per year, according to city officials. That’s more than Yellowstone National Park. 

Sanitas is particularly popular among runners. In October 2003, residents hosted a race from the bottom to the top of the mountain, dubbing it the Cardiac Arete, a general climbing term for any sharp mountain ridge. To be eligible to race, runners had to complete three hours of trail work. The following year, the city banned all competitive events on open space to reduce environmental impacts. The race disbanded. 

The city’s 2023 trails budget is about $4 million, supported primarily by city sales taxes.