OSO — The timeline for rebuilding a stretch of the Whitehorse Trail wiped out by the deadly mudslide that tore through this community in March has been pushed back a year.

Officials need additional time for planning and permitting. Meanwhile, they continue to monitor river levels and multiple washouts along the trail.

The county originally hoped to rebuild the mile-long segment of trail this summer, parks and recreation director Tom Teigen said. After conversations with state and federal teams in late November, it became clear that such a timeline wasn’t realistic, he said.

Instead, the county aims to finish plans and paperwork in 2015, followed by construction of the trail in summer 2016. The goal is to install at least two new culverts to help manage water flow in the area, similar to the approach taken in rebuilding Highway 530 through the slide zone.

The county is working with the Federal Emergency Management Agency on trail repairs in the slide area. They need to factor an altered landscape and unpredictable river into their plans.

The mudslide that killed 43 people and destroyed the Steelhead Haven neighborhood also changed the behavior of the North Fork Stillaguamish River in ways that are still being studied. The Whitehorse Trail skirts and crosses the river and its tributaries in a number of places on the path’s 27-mile route from Arlington to Darrington. At least two spots along the trail have been washed out this year, including a stretch that parallels Highway 530 in the heart of Oso, just west of the community’s fire hall.

The washout happened days before Thanksgiving on a stretch of trail that borders Deer Creek, a tributary of the North Fork Stillaguamish. That segment of trail had to be closed, Teigen said. However, it’s near enough to the road and the shoulder is wide enough that locals who use the trail regularly have been able to get around.

“And we’re certainly not encouraging any non-locals to be up on that corridor in these winter months,” Teigen said.

There is another washout on the trail near Darrington that crews have been monitoring for a while, he said.

The U.S. Geological Survey has installed extra river gauges along the Stillaguamish to track water levels and help provide an alert for potential flooding.

“Lots of folks are watching it and we’re putting together a plan of action,” Teigen said.

Along with the gauges, rangers visited the trail near the latest washout in the days immediately after Thanksgiving, he said.

The trail has been a busy place for rangers and other workers during the last six months. Crews hired by Workforce Snohomish through federal emergency relief funds spent the summer cleaning up the trail. They cut back brush, cleaned out garbage and widened the walkway, especially near Fortson Mill, a key access point for the trail.

Though segments of the trail, particularly those with bridges, remain closed pending repairs and safety upgrades, the parks department is on its way to creating a continuous recreational path between Arlington and Darrington. Officials hope the route will become a boon for businesses in Arlington, Darrington and the communities in between, including Oso.

The effort has received some solid backing in the private sector as well. Teigen expects that at least two of the old, unstable bridges along the trail to be repaired and upgraded by the end of the year thanks to a $301,000 private donation.

“Crews are out replacing railings and decking right now with some of our donated funds,” Teigen said.

The trail is an old Burlington Northern Railroad line, and 14 bridges on the route are in need of updates.

Another donor gifted the county with 30 acres adjacent to the trail near Fortson Mill and the parking area there. The county signed off on the donation the day before Thanksgiving. It gave Teigen something extra to be thankful for, he said. The property can be used to improve access to the trail and draw more people to the location, though specific plans have not yet been made.

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