(Fremont County, WY) – Slide stabilization work is under way as part of an $8.78 million project adjacent to US20/WY789 between Shoshoni and Thermopolis at the north edge of the Upper Wind River Campground.
The prime contractor is Oftedal Construction Inc., of Casper, and the slide stabilization subcontractor is Condon Johnson and Associates, Inc., of Kent, Wash
“Work started Oct. 27. You can see where the slide has moved the last couple years,” said Wyoming Department of Transportation project engineer Jordan Erz of Worland.
“A visual tension crack is visible in the highway’s right turning lane into the campground. Geology inclinometers show the slide plane beginning about 50 feet below the highway.”
Erz said the contractor is placing 179 aggregate columns in an area 50 feet wide and 700 feet long between the highway and river.
“The 179 aggregate columns are each six feet in diameter and are being drilled and placed 40 feet below the level of the Wind River,” he said.
“These columns will act as a shear key to catch the toe of the slide, with the slide surface actually under the river level.”
The slide stabilization work includes two phases.
Phase 1 consists of two rows with a total of 92 aggregate columns, and Phase 2 has another two rows of aggregate columns.
“During Phase 2, the contractor will excavate material at the toe of the slide so the columns can be placed. The area will be rebuilt as each column is placed to maintain slope safety,” Erz stated.
“If the entire toe of the slide was removed at once, we would be in danger of losing part of our highway. Condon Johnson hopes to get all shafts drilled and placed before Christmas, but that schedule could change.”
The Wind River Canyon slide stabilization project includes slide repair, grading, slide stabilization rock (SSR), manual rock scaling, rock fall mitigation and other work on US20/WY789 beginning at milepost 115.9 through 123.12 inside the canyon between Shoshoni and Thermopolis.
Subcontractor Midwest Rockfall has completed rock fall mitigation work until next spring.
“This subcontractor’s work in the spring will include installing rock bolts, rock fall mesh, a rock attenuator system, and other items near the highway tunnels,” Erz continued.
Contract completion date is Nov. 30, 2022.
Project questions may be directed to WYDOT Resident Engineer Kaia Tharp, P.E., at (307) 864-3200, or by email at [email protected]