Super-saturated soils and heavy runoff are factors in recent slide in an area known for unstable slopes
By Bob Berwyn
SUMMIT COUNTY — A large mudslide on Keystone Mountain inundated an employee housing complex near the Mountain House base area, damaging several exterior decks and walkways and covering several hundred feet of a road with mud a couple of feet deep.
The mudslide happened June 2, the same day the Keystone Gulch wildfire started, according to Keystone spokesman Ryan Whaley. Since then, crews have cleared the road and there are no impacts to summer operations at the resort. Whaley said the employee housing units were not occupied. There may be some water damage inside of some of the units, but the extent hasn’t been determined yet. The mud piled up to just below the windows of the units on the lower level.
The slide was on a slope above the very bottom of the Schoolmarm Trail, just east of the Keystone Medical Center. It ran several hundred feet down the slope and was at least 200 feet wide, tearing up big trees and moving huge boulders down the slope. Silty water ran around and between the buildings of the housing complex and all the across the Pika parking lot, where crews were able to use sand bags and straw bales to trap most of the sediment before it reached the Snake River, according to U.S. Forest Service winter sports ranger Joe Foreman.
Foreman said he was inspecting the slide when the call for the Keystone Gulch Fire came in. The front side of Keystone Mountain has several areas known for geologic instability that are prone to mud flows. Several years ago, the Ina’s Way trail was damaged by a mudslide.
Foreman said a Forest Service hydrologist has already looked at the slide, but suppressing the Keystone Gulch wildfire was the highest priority for the agency the past few days. The slope will probably require some restoration and reseeding this summer.