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Aht’Wy Interchange

An interchange will provide safer access to Aht'Wy Plaza residents and local businesses.

After the structure is built, the Idaho Transportation Department will assume ownership and maintain it as part of the public transportation system.

Construction

Due to rising costs for essential materials like steel, concrete, asphalt and fuel, both the NPT and ITD have delayed advertising this project for construction. While the project will still make use of $19 million in grant funding, costs have escalated since the grant was announced in September of 2020.

In response to price increases, the NPT has contributed an additional $1.2 million to construction, but more recent estimates call for another $5.5 million. To cover this increase, the project was submitted for additional federal funding.

Construction delayed

Aht'Wy Plaza: Interchange Design

The interchange will include a bridge over the highway and four ramps to access the plaza near the east entrance.

The four-lane highway will be separated by concrete barrier, eliminating the existing median, turn lanes and acceleration lanes, to make room for ramps in ITD right of way and avoid environmental impacts. North of the interchange, the grassy median will remain. Retaining walls will be built to support the elevated ramps.

The bridge over US-95 will include a sidewalk and broadband conduit.

The parking area just north of the east entrance will be shifted south to provide the Army Corps of Engineers access to maintain the nearby wetland mitigation site for the Lower Granite Dam (labeled as the goose pasture). The old parking area will be restored with natural vegetation.

 

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1996
Aht'Wy Plaza opens casino with plans to expand
1997
Traffic study conducted to look at how growth would affect drivers
1998
Traffic study identifies need for full interchange upon completion of facility expansion
January 2001
ITD and NPT agree to phased improvements at entrances to handle growth
Fall 2002
Phase one completed with lighting, acceleration lane at east entrance and right turn lanes at both
June 2006
NPTEC passes resolution to pursue interchange instead of the remaining phased improvements
July 2009
NPT hosts public meeting to review alternative designs for interchange
September 2009
Preferred alternative is selected and design continues
2012-2017
NPT works with the Army Corps of Engineer (ACOE) to address concerns over the interchange's design
March 2018
Interchange design adjusted to minimize impacts to ACOE property
Summer 2018
Concrete island constructed at west entrance to restrict left turns from exiting drivers
December 2018
New signs that flash are placed near the entrances, and ITD joins other agencies in emphasis patrol
January 2019
Final design begins, and a road safety audit is conducted
February 2019
Final report from road safety audit delivered
May 2019
Audit improvements made to east entrance
September 2020
Tribe awarded BUILD grant
September 2020

$19.1 million grant awarded

In September 2020, the Nez Perce Tribe was awarded a $19.1-million grant to construct the interchange.

May 2019

Adjustment made to right turn lane into east entrance

Work will shift the right turn lane into the east entrance to improve line of sight, per the joint audit's recommendation.

Read more
Road safety audit: final report

February 2019

The road safety audit team provided the final report in February which included a range of options that could be constructed in advance of the planned interchange. Both NPT and ITD are moving forward with options for the east entrance, which include adding an acceleration lane for eastbound traffic and widening the westbound right turn lane to create separation between turning and through traffic.

Work on these interim improvements could begin in spring when weather conditions allow for quality paving and once funding is secured.

January 2019

Road safety audit: initial results

ITD hosted a road safety audit to develop other short-term solutions that could be implemented before construction of the interchange. The audit provided NPT several options to pursue with ITD, which will be further detailed in a final report scheduled to come out in February.

Initial results news story

Project
Updates

Due to rising costs, both the NPT and ITD have delayed advertising this project for construction as of April 2022. In response to price increases, the NPT has contributed an additional $1.2 million to construction, but more recent estimates call for another $5.5 million. To cover this increase, the project was submitted for additional federal funding. Read more.

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