"When people actually take a pick and a shovel and start moving earth or pouring concrete and building structures, that's a problem," said Maura Olivos, sustainability coordinator and ecologist for the Alta Ski Area.
The bikers didn't just cut down a few bushes. The rogue trail through the Albion Basin included jumps, berms and other features constructed of wood and concrete.
"It can be a pretty bad situation up here," said Olivos. "Number one, it can really damage the environment. It's a sensitive area. At the bottom of the work site, there's a wetlands area."
In addition, the trails "are very dangerous and unsafe. There are features that just aren't built to safety standards."
That creates a liability problem for the U.S. Forest Service and Alta if the riders injure themselves or others. It's not just a moose they might run into the illegal trail crosses through campgrounds.
"These folks often are wearing body armor," said Steve Scheid, environmental coordinator for the Forest Service. "They're just blasting through."
The Cottonwood Canyons Foundation, Alta Ski Area, U.S. Forest Service, Friends of Alta, Town of Alta and REI teamed up to organize the volunteer effort on Saturday. About 100 volunteers wielded tools to dig out the unauthorized features and plant Engelmann spruce, Sweet-vetch, coneflower, sage and different varieties of currant bushes, serviceberries and snowberries all grown from seeds handpicked in the area and nurtured at the Alta Ski Area nursery.
"You really see the power of collaboration here and the love of this place," said Claire Woodman, Alta's assistant town administrator. "If we have all these people coming up and they're running amok, that's not good. But we have this opportunity to tell them what a special place this is and why it's important to protect it."
"We're hoping that more awareness will help people come to the table to become part of the process," said Jessie Walthers, executive director of the Cottonwood Canyons Foundation.
In some cases, the trail builders may not realize what they're doing is wrong. In others, they clearly do.
"They're out there at night building trails with head lamps on," Scheid. "It's very difficult."
And the Forest Service needs the help of volunteers.
"That's how we accomplish this," Scheid said. "We don't have the resources to even find these trails, much less address them."
The various groups all went out of their way to say they are not out to confront the rogue trail builders.
"I don't want people to think that we're against downhill mountain bikers. We're not," said Matt Zumstein, a natural resources and recreational manager for the Forest Service. "But they have to make sure they're not impacting our resources in a negative way."
Which, in this case, means going elsewhere.
"We don't like to shut things down," Scheid said. "We want to provide a reasonable alternative. In the watershed, we couldn't find a reasonable alternative."
Saturday's event was just one of many the groups coordinate throughout the year.
"We're always looking for volunteers," said Walthern. "This is a very important area, and we can always use help."
O For a list of summer volunteer stewardship projects, go to bit.ly/1aCLwht