ITD gathering input on major plan to revamp Blackfoot I-15 corridor

BLACKFOOT – Community members have a chance to share their thoughts on a plan to redesign an increasingly used section of interstate.

The Idaho Transportation Department held two open houses on Wednesday and Thursday, allowing members of the public to make comments on its plans to expand the traffic capacity of Interstate-15 between Fort Hall and Blackfoot. People who weren’t able to attend either of the meetings will still be able to view the plans and make comments online until May 15.

“We would like to know… whether or not there are issues that our engineers have not been able to identify yet,” said ITD District 5 spokesman Justin Smith. “We don’t know everything, and so it’s important for the community to speak up and have their voices heard so that we can plan appropriately.”

These plans would make significant changes to this interstate corridor, widening it to three lanes of traffic, and rework both interchanges to the north and south of Blackfoot. While there are still decisions to be made on these parts of the project, ITD has already decided on a final design for widening the interstate between Fort Hall and Blackfoot.

The parts of the project the public can comment on are split into three areas of focus:

• Replacing the South Blackfoot Interchange
• Widening the interstate between Exit 89 to Exit 93
• Replacing the US-26/Blackfoot Interchange

Replacing the South Blackfoot Interchange

ITD has presented the public with three options for how this interchange would be rebuilt, recommending option 3. The red sections of road represent existing roads that would be eliminated.

Option 3 would add an overpass to the interchange, allowing southbound travellers to exit and then drive over the interstate to highway 91. This would eliminate the current exit and the southbound entrance, allowing people to enter on the same road, regardless of whether they’re going north or south.

This would address one of the main issues ITD is trying to fix, particularly the short distance people have to speed up and slow down as they exit the interstate.

“The biggest issue that we’re seeing there is the short distances for deceleration and acceleration as you go through that interchange… and we’re looking at ways to give traffic more room to accelerate when entering the interstate and to decelerate when they’re leaving,” Smith said.

The design options ITD presented are preliminary ones. It plans to develop the design plans this year and next year, and host another community open house to request input in 2026. It then plans to finish the design plans in 2026 and 2027, and then begin construction in 2030.

Widening the interstate between Exit 89 to Exit 93

ITD has presented the public with two design options for how the interstate between Blackfoot’s two exits could be widened. Design Option 1 is closer to its final design for the widening of I-15 between Fort Hall and Blackfoot, with a shoulder and barrier wall, rather than a median like in Design Option 2.

The transportation department recommends the first option, because it minmizes potential environmental impacts, simplifies the construction process and accommodates future population growth.

“The secret is out. Idaho is a nice place to be, and so we’re seeing a large increase in population,” Smith said. “We’re trying to meet that issue now, rather than waiting until it becomes critical.”

ITD is currently conducting a project to widen I-15 between the Northgate exit and Fort Hall to three lanes of traffic. Its long term plan for the interstate is to eventually widen it out all the way to Idaho Falls.

“But we have to take it in sections because of the funding,” Smith said.

ITD will further develop these design plans in 2025 and 2026, hosting an open house to request community input that year. It then plans to complete the design plans by 2027, and start construction at a date that’s still to be determined.

Replacing the US-26/Blackfoot Interchange

Because ITD already held an open house in 2023, it has already determined that it will build what it calls the Improved Diamond Interchange design. On one of the project boards it presented, the department says the design will accommodate future growth and improve safety and mobility for interstate travellers.

The ramps on the interchange will be lengthened, and a four foot buffer will be added between the traffic lanes and exit lane. Highway 26 will have two through and two left turn lanes going under I-15, and there will be a 23-foot clearance, accommodating oversized trucks and megaloads.

In addition to this, ITD will add a 14-foot high, approximately 1,700 foot long soundwall between the interstate and Jensen Grove Park, with a concrete barrier between traffic and the wall. This was decided after conducting a noise analysis to find the impacts the new project will have on the recreational area.

Construction is scheduled to begin in 2031, with the final design plans being completed either this year or next year.

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