The rhythmic "thump, thump, thump" drumbeat foretold the imminent approach of the single-rotor Bell "Huey" helicopter. Taking a wide, arching path across the bright blue sky, the pilot guided the helicopter in a circular approach, dropped steadily, and began lining up with three workers clad in safety orange positioned on the ground next to the pick-up point out Warm Springs Creek west of Ketchum.
Grabbing the long, slender cable attached to its underbelly, the ground crew quickly attached the Huey's next round of cargo. Moments later, the helicopter lifted off with a several-thousand-pound load of woody mulch and then disappeared behind a nearby ridge.
For hours on end—from nearly sunup to sundown, local U.S. Forest Service officials said Monday—pilots guiding the Huey as well as a second helicopter of a different make—a specially designed heavy-lift K-Max—made repeated five-minute turnarounds over the weekend and into early this week. Their only breaks were to fill up with fuel.
Evidence of their efforts are now splashed across almost 400 acres of burned-over hillsides inside the much larger 48,520-acre Castle Rock Fire area. Where last fall's racing wildfire burned hottest and closest to rural homes, hundreds or thousands of feet below in areas of the lower Warm Springs Creek drainage, inside and just upstream from the Ketchum city limits, the helicopters dropped numerous loads of straw and wood mulch.
Depending on the severity of moisture-laden thunderstorms that pass over the region later this summer, the several inches of organic material should help slow or stop erosion and dangerous landslides that could devastate homes and lives below.
High up on the open south-facing Warm Springs Ridge, the blackened north face of Guyer Ridge and further out Warm Springs, Forest Service spotters were positioned to keep watch over the individual drop points selected for the treatments, said John Chatel, a fisheries biologist for the Sawtooth National Forest. Chatel was selected to lead the federal Burned Area Emergency Response (BAER) team assigned to come up with the post-fire recovery options for the large burn area west of Ketchum.
Looking uphill during a media tour of the recovery areas Monday, Chatel pointed to one of the spotters skylined on top of a nearby ridgeline.
"They're talking back and forth with the pilots," he said. Wishing to burn as little fuel as possible, the private contractor assigned to the job by the Forest Service—Mountain West Helicopters out of Alpine, Utah—was on track to finish dropping the straw and wood mulch on the selected spots as early as Tuesday, June 10.
Chatel said that where the blaze burned most intensely during 20 smoky days last August and September, the result was hydrophobic soils. In essence, these soils are incapable of absorbing water and can thus lead to disastrous mud and debris flows after particularly heavy rainfall events, he said.
The series of large landslides that blocked portions of Warm Springs Road in the weeks after the fire were evidence of the seriousness of these hydrophobic soils.
Chatel said the impacts of these soils will last as long as three to five years, depending on the orientation of hillsides. Where they face north, slopes will remain hydrophobic longer because they burned the longest and most intensely because of the heavy tree cover and woody debris that blanketed the ground, he said.
Forest Service officials said the entire erosion control contract conducted by Mountain West Helicopters during the past few days will cost the federal government upwards of $800,000. Sites for the targeted mulch drops were selected because of their proximity above threatened homes, which could be damaged by overland flows and sediment.
Many other hillsides located throughout the Castle Rock Fire area that burned just as intensely but aren't adjacent to threatened homes will not be similarly treated. Rather, Mother Nature will be allowed to reclaim these burned-over lands on her own schedule.
Straw for the project had to be certified free of noxious weeds before it could be transported into the area, said Sawtooth National Forest Botanist Kim Pierson, another member of the BAER team.
Looking up to the greening hillsides near Penny Lake west of Ketchum, Pierson expressed delight with how well the fire area looks to be recovering since last fall. She said the cool, wet spring the area has experienced has actually been a bonus as it has allowed native plants to grow larger and produce more flowers, which in turn will produce more seeds for future plant growth.
"It's exceeding my expectations," she said.
Pierson said the resurgent plant growth should help shield burned hillsides from disastrous landslides. Separate plantings of bitterbrush and sagebrush already conducted inside the fire recovery area will also help control erosion, she said.
Pierson said she is also pleased that Forest Service officials decided against conducting a large-scale reseeding effort last fall. She said the only reseeding they did was in the Limekiln drainage on the fire's south end in the Greenhorn Gulch area.
Because Limekiln burned so hot and damaged plants so extensively, officials decided that placing seed there was advisable, she said. Elsewhere, they felt reluctant to bring in seed that, while native to the region, isn't as acclimatized to the local area, she said.
Burned hillsides on the heavily timbered north face of Guyer Ridge thousands of feet above threatened homes, above, have been treated with straw dropped by helicopters to help control erosion and disastrous landslides. Photo by Willy Cook
