The 25-acre Porcupine Landslide, 17 miles from Alpine, Wyoming, is continuing to move.
Bridger Teton National Forest officials said the February 28 landslide is comprised of roughly 500,000 cubic yards of earth, which has slid over a quarter mile stretch of the Greys River Road. That portion of the road was destroyed. They estimate a little over one million tons of earth still hasn’t stabilized and is subject to unknown variables.
“We still haven’t hit peak runoff and while the slide is still moving, it has slowed down since last month,” said Greys River District Ranger Justin Laycock.
The forest is working with consultants and partnering agencies to find contractors, funding, equipment and personnel ready to work as soon as the landslide stabilizes. The biggest concern is still a 14-vertical feet of water behind the landslide dam.
“The fact that the landslide is still unstable and that the Greys River is continuing to carve a new channel to the west of the debris dam created by the landslide has not stopped the Bridger-Teton, or its partners, from getting everything lined up so work can begin as soon as it is possible to enter the area and make effective changes,” Laycock said. “Last week we had an excavator on site, improving drainage and helping natural water flow in order to help get the area ready for drill pad installation so we are in a position to start work on de-watering the site,” he said.
Simplot, Smokey Canyon Mine, and WYDOT are lining up equipment to begin work when it becomes feasible. Lincoln County will also participate in initial drilling.”We plan to work with Lincoln County to acquire additional 3D imagery with another unmanned aerial system (UAS) flight on the site visit on the 30th as well,” Laycock said.
Although the Alpine access and Greys River Corridor is closed for 10 miles, visitors can still access the forest beyond the closed area by three other routes. There is still a risk to recreationists along the Greys River Road below the slide if the debris dam fails. The Forest has identified no camping areas along the lowest lying portions of the route and has a commitment from Lincoln County to assist in rapid evacuation of the corridor in event of the flooding emergency.
More information is available at the forest website here.