Sargent Mountain in Acadia National Park is benefiting from an important project aimed at protecting the fragile terrain on its peak.

Using rocks and stones mostly from a massive cairn on Sargent Mountain, workers are completing a new 50-foot causeway on the Sargent South Ridge Trail. The work is being done to encourage hikers to stay on the trail instead of venturing to the subalpine zone around the mountaintop.

From left to right, Liam Hassett, 16, of Cleveland, Ransom Burgess, 18, of Bar Harbor and Billy Brophy, 15, of Hyattsville, Maryland swing sledgehammers to bust stones into tiny pieces for creating a new 50-foot-long causeway atop Sargent Mountain in Acadia National Park. The three are members of the Acadia Youth Conservation Corps.

The new causeway is being constructed with two layers – rocks and stones on the bottom and gravel stones on top, along with a stone border on each side. The work is shoring up a section of the trail that was deeply eroded, said Acadia Trails Foreman Gary Stellpflug on the peak on Tuesday.

“It’s really a good project,” Stellpflug said while he and other workers moved dozens of stones and rocks into the new trail section.

“I’d love to use some soils but there aren’t any.”

Acadia National Park Trails Foreman Gary Stellpflug, to the left in foreground, watches while Acadia trail workers Christa Singley, left, and Ivan Klusyk, right, carry a heavy stone on a gurney to help build a new protective causeway on Sargent Mountain. The rock gurney was designed and donated by Morris Yachts.

The 1,373-foot Sargent, the second highest peak in Acadia behind Cadillac, and other Acadia summits are home to some unusual or rare subalpine plants, supported only by a thin layer of soil. The peaks have long been vulnerable to heavy foot traffic.

Stellpflug and Charlie Jacobi, Natural Resource Specialist for Acadia, led 16 others dedicated to the project.

It was tough, deliberate work. In order to create the top layer of the causeway, some crew members busted rocks with sledgehammers.

On another part of the peak, Acadia trail workers Ivan Klusyk and Christa Singley placed one 150-pound stone in a gurney and hauled it to the work site.

Charlie Jacobi, Natural Resource Specialist for Acadia National Park, hoists a bag of rocks over his shoulder on the peak of Sargent Mountain.

“This is trail work,” Jacobi said. “That’s how it gets done. One rock at a time.”

Many on the crew filled bags with rocks from the giant peak cairn and carried the sacks to the emerging causeway.

“That’s the name of the game,” Jacobi said. “Grab a bag, fill it up and dump it.”

The project on the Sargent South Ridge Trail is being partly financed from a $2,000 grant from the Waterman Fund, a nonprofit that works to protect the open summits of the Northeast.

The Friends of Acadia, a private, nonprofit group that supports the national park with private donations, and Acadia National Park are also providing trail crew.

The 3-day project was being completed by Acadia Youth Conservation Corps and Ridge Runners, both sponsored by the Friends of Acadia, along with regular Acadia trail crew such as Stellpflug, Peter Colman, a 22-year trail crew leader, Klusyk and Singley.