The Montana Department of Transportation is progressing on its long-planned Gore Hill interchange project that includes a roundabout, a new bridge and relocating the Tri Hill Frontage Road.

During the Feb. 24 airport board meeting, representatives from MDT and RPA, the consultant on the project, updated the board, airport, 120th Airlift Wing and Holman Aviation officials on the project.

In 2015, MDT developed the I-15 Gore Hill to Emerson Junction Corridor Planning Study in partnership with the Federal Highway Administration and in coordination with the Great Falls Metropolitan Planning Organization.

The purpose of the study was to determine potential improvement options to address safety and operational concerns within the interstate system through Great Falls.

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The report identified recommendations to address the transportation needs in the area through the planning horizon of 2035.

Among the recommended improvement options were the addition of a southbound auxiliary lane between the Gore Hill and 10th Avenue South Interchanges and intersection improvements at the Gore Hill Interchange.

The Great Falls Long Range Transportation Plan 2018 Update also included recommendations to make improvements to the Gore Hill Interchange as outlined in the Corridor Planning Study. Various public involvement strategies were used to engage key stakeholders and the public throughout these past planning efforts.

Smith and others presented at the Nov. 25 airport board meeting and said the project received a $19 million Multimodal Project Discretionary Grant through the U.S. Department of Transportation in 2024, which is why the project has picked up speed.

The funds must be obligated by September 2028 and spent by September 2033.

The current design includes:

• I-15 Gore Hill interchange overpass bridge will be replaced. The new structure will be built to the east of the current overpass to keep the interchange open during construction. The new bridge will be wider and include shoulders and a sidewalk.
• two single-lane roundabouts will be added on 31st Street Southwest at the I-15 southbound off-ramp and northbound on- and off-ramps. A sidewalk will be added between the roundabout intersections.
• an additional southbound lane will be added to I-15 between the 10th Avenue South and Gore Hill interchanges. The lane will exit on to the southbound Gore Hill Interchange off-ramp.
• Tri Hill Frontage Road and 31st Street Southwest intersection will be relocated to the south.

The new bridge design and roundabouts will accommodate over-sized trucks through the intersections, according to MDT.

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Jacquelyn Smith of RPA said that they’re continuing to develop final plans, including road design, bridge plans, and details for utilities, electrical, signage and striping.

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Right-of-way plans have been finalized and MDT received authorization to start those acquisitions which triggered the need for an appraiser.

Based on feedback from the airport during a November meeting, Smith said they hired someone with experience with the Federal Highways Administration and Federal Aviation Administration.

She said that they’d just started developing traffic control plans for the construction and asked the group if there were events or details they needed to be aware of in their planning.

Col. Todd Mortag of the 120th Airlift Wing said the wing was hosting the Roar Over the Rockies airshow in August 2027 featuring the U.S. Navy’s Blue Angels.

The MDT/RPA team said construction would likely begin in the fall of 2027 and be wrapping up in 2029, so would hopefully not conflict with the airshow.

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Jimmy Combs, MDT’s Great Falls projects development engineer, said that access will be retained throughout construction.

“That’s a must,” he said, but it will be affected by the construction and there may be reduced lanes.

He asked if there were other days, hours or events that are less critical for operations that would be helpful in their planning.

John Faulkner, airport director, said it’s not always predictable, but the bulk of traffic is between 4:30-6 a.m. for the morning flights, then a few flights throughout the day. He said planes are getting bigger, which could increase bursts of traffic.

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He said his bigger concern was that with more development around the airport, they’d only get about 20 years of capacity out of the MDT design before it was overcrowded.

Smith said they looked at the traffic numbers and design multiple times, multiple ways.

“We are feeling confident,” in their traffic projections and the buffer included in the plan.

Combs said that MDT did an original traffic study for the project and two supplements, including one at the request of the airport to account for projections and growth related to the proposed development around the airport. They used 2024 traffic data, he said.

Dwight Holman, owner of Holman Aviation, said that traffic backs up when the Guard and Avmax releases in the afternoons.

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Smith said they expect appraisals to be completed this summer with acquisitions through the fall. They’ll also be doing environmental permits and utility work through the fall.

She said the project is scheduled to go to bid in 2027 and construction to start at the end of that year.

“It’s a complex area,” she said.

They’re in the right of way phase, at the appraisal and valuation stage. Next they’ll move to negotiations and once signed agreements are in place, then construction can begin, she said.

The MDT/RPA team plans to report to the airport again when they have the traffic control plans drafted.