ITD settles on three options to solve I-15/US 20 congestion


IDAHO FALLS — It’s going to be at least seven years before construction begins to fix the Interstate 15 and U.S. Highway 20 interchange.

A proposal to realign Highway 20 to resolve current congestion issues at the interchange is causing homeowners in the area concern. However, that proposal is only one of three being considered, and the Idaho Transportation Department it is still gathering information. Nothing has been decided yet.

“The earliest you’d see construction on any of these projects is 2026,” ITD project manager Ryan Day told

A letter concerning that proposal, called Alternative H, is circulating among residents who would be affected if ITD adopts that option.

Alternative H realigns U.S. 20 to the north. This would cause U.S. 20 to cross 5th East/Lewisville Highway, 5th West/East River road and pass next to Fairway Estates.

“Many of our neighbors on 5th West would lose their homes. All residents will be subject to years of construction, road noise, busy traffic, significant loss of property values and our quiet country neighborhoods would become a hub for a major five-lane highway,” the letter states.

Day acknowledged there are pros and cons to each of the different options.

“All three of the current build options are good, solid options to be built. The pros and cons to some of them impact more business. … Some negatively affect farmland. But every one of them addresses our mobility issues and our safety issues that we’re so concerned with,” he said.

He said ITD wants feedback on the three different interchange solutions. The department created a website detailing the project and offering a place for people to offer their thoughts. To visit the site, click here.

Day said officials hope to conclude this first phase of information gathering sometime this fall or winter. Once that is done, there are still years worth of items that have to happen before construction begins, and all of that is contingent on if funds are available.

RELATED: ITD taking public input on changes to 6 highway interchanges in Idaho Falls

The next phase of the project is beginning the National Environmental Policy Act review process. NEPA is meant to ensure the decisions made projects like the I-15 and U.S. 20 interchange are environmentally sound.

“We’d hold public hearings, continue to gather information and we would start acquiring environmental documents. At that point, it would take a minimum of two years to get through the NEPA process. Then we’d have to design the project,” Day explained.

On May 16, ITD conducted its third public hearing. That public hearing is available online. People can comment on the information provided in the hearing through June 14.

Here are the three interchange options:

Alternative C

Alternative C would add lanes to separate the through-traffic from the local traffic between the interchange. It would require new retaining walls and bridges.

    Features & Benefits

  • Reduces weaving concerns between I-15, exits 118 and 119 by providing direct ramp connections from I-15 south of exit 118 to U.S. 20.
  • Adds a new river crossing to the north at Higham Street for local street connectivity.
  • Provides opportunities to develop pedestrian and bicycle connections between I-15 and U.S. 20.
  • Separates the local and through traffic between exit 118 through City Center/Riverside exit 308.
  • Challenges

  • Eliminates U.S. 20, exit 307, at Lindsay Boulevard which will impact direct access from U.S. 20 to area hotels.
  • Elevated structures and new bridges are required.
  • Could impact Temple View Elementary School, Antares Park and the surrounding neighborhood as well as neighborhoods east of Snake River.
  • Could impact traffic during construction as it reconstructs much of the existing roadways.
  • Weave with the merge of the direct ramps near Science Center will be a challenge.
I15US20 C
Alternative C | Courtesy ITD

Alternative E

Alternative E moves the existing I-15 interchange exit 119 closer to the airport. It would require adding separated through lanes and frontage roads as well as the conversion of the existing U.S. 20 Grandview roadway to a local street.

    Features & Benefits

  • Removes weaving concerns between I-15, exits 118 and 119, by connecting them with direct access ramps and realigning U.S. 20 to the north.
  • Moves regional traffic from I-15 through direct access ramps that lead to and from U.S. 20.
  • Provides direct access from I-15 via a new interchange near the Idaho Falls Airport.
  • Challenges

  • There are impacts to industrial areas near the airport, residential areas, Freeman Park and a church.
  • May not resolve the congestion issues on I-15 due to the proximity of exit 119 at Grandview Drive from the new airport interchange.
I15US20 E
Alternative E | Courtesy ITD

Alternative H

Alternative H realigns U.S. 20 to the north and provides a connection to U.S. 26 at East 49th North. Existing U.S. 20 between Johns Hole and East 49th North would require changes to convert it to a local street.

    Features & Benefits

  • Realigns U.S. 20 to the north of downtown Idaho Falls, providing for a new connection to U.S. 26, and allowing regional traffic a direct connection.
  • Improves the interchanges in town, including converting I-15, exits 118 and 119 to a split diamond interchange to remove weaving and backup on I-15.
  • Converts current U.S. 20 to a local street.
  • Allows for building in phases with the realigned U.S. 20 and connection to I-15 first, followed by the split diamond interchange improvements to exits 118 and 119 and then the connection to U.S. 26 to be built later when appropriate.
  • Potentially reduces the length and severity of the delays and impacts to the traveling public during construction by mostly building off the existing roadway alignments.
  • Challenges

  • Alignment goes through a landfill, which would require mitigation.
  • Impacts to farmland and adjacent neighborhoods
  • I15US20 H
    Alternative H | Courtesy ITD
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