Hillsides burned by the 2007 Castle Rock Fire near Ketchum continue to pose a significant threat of sliding, emergency officials said.
That fact became abundantly clear this week as heavy and sustained rainfall saturated soils in the Warm Springs Creek drainage to the point where they couldn't absorb any more. Once that critical point was reached, it was only a matter of time before portions of the rain-swollen hillsides collapsed, dumping a muddy and debris-filled soup into the valley bottom below, experts said.
"It just let loose," said Joe Miczulski, recreation and winter sports specialist for the Sawtooth National Forest's Ketchum Ranger District.
In at least four spots, the mudslides inundated sections of Warm Springs Road, blocking all travel up and down the rural roadway west of Ketchum. The owners of several outlying homes were temporarily kept from leaving their residences as crews from the Blaine County Road and Bridge Department struggled to clean up the soupy mess.
The road was finally cleared and opened to canyon residents on Tuesday. Another round of thunderstorms that brought heavy rain and hail on Wednesday convinced county officials to keep the road closed to the general public until the situation improves.
Early Thursday, Blaine County Disaster Services Coordinator Chuck Turner warned that the road could remain closed at least until Sunday or Monday, when the National Weather Service has predicted a possible break in the weather.
Miczulski said another slide that happened farther out Warm Springs near Frenchmen's Bend hot springs was very close to the spot where a number of large mudslides occurred weeks after the 2007 fire. Those earlier slides completely filled the manmade pools at the hot springs and also dammed up long stretches of Warm Springs Creek.
This round of mudslides is proving that the chance for mudslides in the burned area hasn't ended, Miczulski said.
According to Turner, the slides are also showing that there's no way of guessing when or where it will happen again.
"It's sliding in places where it hasn't slid before," Turner said.
Forest officials haven't had a chance to look into whether rehabilitation work done last summer by the Sawtooth National Forest in places such as Guyer Ridge has helped deter any sliding. Last June, helicopters dropped straw and woody mulch on about 400 acres of the most impacted areas of the burn in the Warm Springs area.
That's out of a much larger 48,500-acre total fire area that saw a mixed intensity of burning. Some areas within the fire perimeter saw no burning at all.
Kurt Nelson, district ranger for the Sawtooth National Forest, said officials will hike to the rehabilitated spots today to determine where the slides began.
Turner, who drove out Warm Springs late Wednesday with two National Weather Service forecasters from Pocatello, said the wet conditions are creating a "slick and nasty" mess, even on areas of the road not hit by mudslides.
"It's still not someplace you want the general public to go," he said. "There was one mud puddle I wasn't sure if I was going to get through."
Local emergency officials are monitoring the situation around outlying homes near burned hillsides in the lower and upper Board Ranch areas. So far, only one home in lower Board Ranch has been impacted by the slides.
Jason Kauffman: email@example.com