OSO — People kept a wary eye on Deer Creek and the bite it took out of the Whitehorse Trail.

For weeks, the washout didn’t grow. The highway was safe.

That changed quickly Monday morning. Crews hurried to shore up the creek bank as water came within two feet of breaching the trail and reaching Highway 530 in downtown Oso. The washout is across the highway from Oso’s fire department, chapel and general store, and about four miles west of the site of last year’s deadly mudslide. “The concern was that if it broke through the trail, it could get to 530,” county public works director Steve Thomsen said.

The Army Corps of Engineers, state Department of Fish &Wildlife, local tribes and multiple county departments coordinated to stop Deer Creek before it reached the road, county parks director Tom Teigen said. Workers put down about 12 truckloads of large rocks to bolster the bank where the trail had washed out. It was the second such effort in the past couple months — the river ate away a chunk of the trail in November, so crews laid down a mix of rocks and woody debris like tree trunks and root bundles.

Officials planned to wait until summer to do any major work on the Whitehorse Trail. They had hoped the temporary buffers put down in late 2014 would hold until the weather was dry and the river low.

“Our hand was forced on Monday,” Teigen said. “It was almost like opening a high-pressure hose on the trail. The way the river was hitting that one spot, we needed to act.”

Gail Blacker, who lives near the Oso Community Chapel, worried the river would break through to the highway. Deer Creek has been gnawing at land on the other side of the highway for years, she said.

“That thing has been eating away at that property,” Blacker said. “Oso just doesn’t need another major catastrophe.”

The county regularly monitors the North Fork Stillaguamish River and its tributaries, including Deer Creek, Teigen said. Additional gauges were installed to track the river after the Oso mudslide on March 22, 2014. The slide killed 43 people and altered the Stilly’s course. Researchers continue to look into how the river has changed and how that could impact flooding.

The Stillaguamish wasn’t the only river running high this week. Flooding swept Snohomish County on Monday and Tuesday, swallowing houses and closing roads.

Most rivers receded by Wednesday morning.

The emergency buffer along the highway in Oso held up. A narrow sliver of muddy, lumpy trail remained above the new rock barrier. A dirt-splattered “Trail Closed” sign lay in a tangle of thorny brush, and yellow warning tape dangled in shreds from the brambles.

The trail needs a lot of work, Teigen said.

“But we feel it’s been reinforced, it’s stable,” Teigen said. “The conversations now are whether we go back in while the water’s receding and do some of the permanent work, or do we wait for the summer?”

The 28-mile Whitehorse Trail corridor stretches from Arlington to Darrington. Less than 10 miles are open at the moment, but the county hopes to complete the trail by mid-summer 2016. That means repairing old railroad bridges, clearing brush along the walkway and completely rebuilding about a mile of the trail that was wiped out by the mudslide.

At least 80 percent of the trail is within a couple hundred feet of the North Fork Stillaguamish or one of its tributaries, Teigen said. The parks department is working to find the best way to manage erosion and washouts along the trail, possibly by reinforcing riverbanks with rounded rocks or natural debris to protect the trail and fish habitats.

“We do believe this is going to be an ongoing concern up there,” Teigen said. “We don’t believe this is the last time we’ll be up there in the next couple years.”

Herald writers Noah Haglund and Rikki King contributed to this report.

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