Ranchester, Wyoming, is a small town located approximately 10 miles from the Montana border. Running near the town is the longest interstate in the U.S., Interstate 90 (I-90), which traverses more than 3,000 miles from Seattle, Washington, to Boston, Massachusetts.

Just northwest of Ranchester, the Wyoming Department of Transportation (WYDOT) and general contractor Croell Inc. are in the middle of a project that touches 8 miles of I-90. The northern end of the project is at the state line of Wyoming and Montana.

This section of I-90 dates back to the mid-1980s. WYDOT recognized that the life span of this section of the road had expired and it was starting to show its age. The surface was due for a rehabilitation.

The average daily traffic on the highway in 2019 was slightly over 2,100, with trucks accounting for 50 percent of that traffic.

"For our area, that's a good amount of traffic," WYDOT Public Relations Specialist Laura Dalles said. "There’s a consistent flow of traffic, which includes locals who live in small communities near the state line and commute to Sheridan and people who are traveling to Billings, Montana, which is 1.5 hours away."

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In addition to the standard mill and overlay, the project includes repairing multiple slope structures, removing four bridges and replacing them with box culverts, repairing two bridges, and realigning 4 miles of eastbound I-90.

There have been regular slope failures along I-90 in the project area. A slope failure happens when the underlying soils, commonly clay, become overly saturated and lose their “sticky” factor. Most of these clays sit on a shale base, offering little to no resistance for the clay to adhere to. The soil becomes too heavy and moves along the path of least resistance and falls away from the slope, encroaching into the shoulder of the highway and potentially into the lane of travel.

WYDOT has been watching one particular part of the project area for several years. This specific slide broached the shoulder and guardrail and required a temporary fix — soil nailing — that would hold until the project could address the issue permanently.

"The repair got us by until we could come through with the project," said Jake Whisonant, WYDOT District 4 Resident Engineer.

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There are large ranches that span both sides of the interstate, so the ranchers need to be able to move their cattle around the area. They utilize machinery passes to move their cattle to pastures on either side of the road. The original passes were bridges that have now been replaced with box culverts. The bridges are 16 feet tall by 15.5 feet wide.

"It's feasible to turn the bridges into box culverts," Whisonant said. The culverts are less expensive to build, install, and maintain.

The team is lining several other culverts that drain out of the median.

"We go through the under drains and line the corrugated metal pipe culverts with high-density polyurethane liner inside the metal,” Whisonant said. “We push the lining through, so it extends to each end of the culvert. The process extends the life span of the culvert."

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The project includes significant slope stabilization work. Over the course of the project, the team expects to remove more than 180,000 cubic yards of failed soil. Much of the fill section dates back to the 1970s and 1980s, when I-90 was built.

The team is replacing the material with scoria. According to geology.com, scoria is a “dark-colored igneous rock with abundant round bubble-like cavities known as vesicles. ... One of the main uses of scoria is in the production of lightweight aggregate. The scoria is crushed to desired sizes and sold for a variety of uses.”

A prominent resource in the area, scoria was created from old coal fires that baked some of the surrounding clay.

"We find scoria is very good, abundantly available, permeable, lightweight, and it doesn't stress unstable materials," Whisonant said. "It's an excellent alternative for super high clay, which is prone to instability, and we've used it to replace slides for several years."

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In northeastern Wyoming, the construction season typically runs from late April/early May to mid/late October. Because of the short season, construction delays can be tough to overcome.

So far, the team has the project on schedule, despite challenging conditions. Croell started excavation in January 2025 and was ready to move forward in the spring.

"The contractor fought the weather [snow/rain] all spring," Whisonant said. "It wasn't unusually wet, but there were the usual spring storms to deal with.”

Another challenge is the logistics of hauling materials. To help solve the issue, the state secured a large portion of right of way in the area, and the contractor built a series of waste areas near the project.

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WYDOT also negotiated with a local rancher to use their private property. The team is putting a significant portion of the material in the area.

The negotiations allowed the state to minimize the distance that hauled materials travel, saving time and money. As part of the agreement, the contractor will reclaim the waste areas to a similar topography as the surrounding areas, place topsoil, and re-vegetate the area into a productive cattle pasture.

Croell and the team began working on the project at the end of 2024. They completed some prep work to ensure they were ready to go when the weather warmed up, allowing the team to stay ahead. Phase one of the project was completed in 2025.

The bulk of the work in phase two involves realigning 4 miles of the highway. The team will move the eastbound lanes closer, 40 to 50 feet into the median. This is being done to remove excessive weight from unstable embankment fills and to greatly increase the interstate’s safety against potential future slope failures.

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The work requires dealing with the subgrade and base. Whisonant said he is concerned about the weather and how it could impact the schedule and work.

"They were able to overshoot the schedule for phase one and bite off some work scheduled for phase two," Whisonant said. "The extra work should help pretty dramatically and puts us in good shape to finish the project on time or even early."

Croell, which is headquartered in Sundance, Wyoming, has worked with WYDOT previously. Whisonant praised the contractor.

"They've done a really good job in their scheduling," he said. He points to the weather challenges in phase one as an example of this.

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"The contractor fought to not impact critical paths and shifted to other work when there was inclement weather,” Whisonant added. “There were no down days, so they were able to mitigate productivity issues."

Croell has also taken a proactive approach when issues arise.

"When they see issues on the horizon, they work with us and make it a true team effort," Whisonant said. "We discuss how we’re going to approach the issue and set priorities."

The project has a $34 million construction budget. The federal and state governments are splitting the cost, with the former covering 80 percent and the latter paying the remainder. The project is currently on budget. Whisonant credits this to the contractor's attention to detail and their collaborative effort with WYDOT.

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When the team completes the project at the end of 2026, drivers on this I-90 section in northeast Wyoming will enjoy a smoother ride and the four-lane highway will benefit from increased protection against landslides.

• Owner/Designer/Engineer: Wyoming Department of Transportation
• General Contractor: Croell Inc., Sundance, Wyoming
• Other Contractors: S&S Builders LLC, Gillette, Wyoming; DRM Inc., Gillette, Wyoming; Keyhole Technologies LLC, Casper, Wyoming; Wilson Bros. Construction, Cowley, Wyoming