OSO — Trees are growing and purple flowers are blooming alongside a 12-foot-wide ribbon of land where workers Monday started flattening dirt and laying down fabric, rock and gravel.

They’re rebuilding the mile of the Whitehorse Trail that was destroyed by the Oso mudslide March 22, 2014.

The plants growing there now are bright against the gray and brown of an uneven landscape. Shattered trees poke out from mounds of earth deposited by the disastrous force of the slide.

An orange temporary fence is being set up on either side of the trail corridor so the crew stays inside the work area, project engineer Nova Heaton said. The contractor also has been trained on treating the site with sensitivity. The mudslide killed 43 people and wiped out a neighborhood.

“We consider this a sacred site,” Snohomish County Parks Director Tom Teigen said. “This is an important location. This is not a normal job.”

Workers are staged at the Steelhead Drive pull-off from Highway 530, next to a memorial grove of cedar trees. During the trail rebuild, which is expected to be done by mid-October, the area is closed to the public. The county is working with families to make sure they have access to the grove, but they’re a rare exception to the closure, Teigen said.

The $980,000 project is being paid for with FEMA money. The trail is being built up and no excavation is planned, Heaton said. The only digging needed is to install two fish passage culverts at stream crossings. The culverts are expected to be built in August.

The rest of the project is fairly straightforward, Heaton said. The ground needs to be flattened and built up with dirt, then geotextile fabric, then large rocks and finally a layer of fine gravel.

“When the slide happened it pretty much covered the entire trail, which originally was on a railroad grade,” she said. “Everything was completely gone, and a railroad grade is a pretty sturdy grade.”

The rebuild is meant to replace what was there before, she said. No new features are being added. Whether the trail has a role in a future memorial isn’t part of the current project.

“The families haven’t decided what they want yet,” said Heather Kelly, emergency program manager and longterm recovery lead with the county. “We’re not making any decisions until they’re ready. The longterm memorial is really owned by these families.”

She contacted the families before work on the trail started.

The Whitehorse Trail has become a focal point for Arlington, Darrington and Snohomish County as they talk about enhancing outdoor recreation options in the scenic Stillaguamish Valley. The work in the slide zone isn’t the only project along the 27-mile trail, which runs from Arlington to Darrington and largely parallels Highway 530 and the North Fork Stillaguamish River.

Near Trafton, crews are rebuilding another portion of the trail where it dropped about eight feet after ballast was removed.

Over the past couple of years, county workers also have gradually replaced decks and railings on most of the trail’s 18 bridges. A private donation is paying for the bridge work, which now includes a rebuild on one that no longer was stable enough to be redecked, Teigen said.

By the end of the year, he expects all but that one bridge will be updated.

The county also is working with the state Department of Transportation to put in designated crossings where the trail goes over Highway 530.

Events already are planned along the trail next year. A memorial bike ride between Arlington and Darrington is scheduled for March 2017, around the three-year mark since the slide. It’s part of the plans drafted for America’s Best Communities, a national contest in which an Arlington-Darrington partnership is a finalist.

The trail should be done in plenty of time for the bike ride, Teigen said.

“It’s really important to the community and families,” he said. “It’s part of the healing.”

The new stretch of trail near Oso connects to partially overgrown segments on either side. From the west, a serene view of the North Fork Stilly in the shade of tall trees gives way suddenly to the openness of the slide zone, where the trees still are young and the view of the broken hillside and the devastation below is unobstructed, except by the green saplings and purple flowers.

“It’s humbling to be out here, just to see the power of Mother Nature,” Heaton said. “The power of Mother Nature took us all off guard.”

Kari Bray: 425-339-3439; kbray@heraldnet.com.