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Idaho Transportation Department Expands I-84 to Contend with Rapid Growth in Boise

by: Larry Bernstein
The Idaho Transportation Department is battling current population growth and preparing for the future with the I-84 expansion in Boise.
The Idaho Transportation Department is battling current population growth and preparing for the future with the I-84 expansion in Boise.
According to the 2020 United States Census, Idaho’s population grew over 17 percent since 2010, making it the second fastest-growing state in the country. Meridian, Idaho, which is approximately 10 miles from the state capital of Boise, was the fourth fastest-growing city in the country, as its population increased by over 56 percent. All this growth means one thing for infrastructure – more is needed. As part of this need to grow their infrastructure, the Idaho Transportation Department (ITD) is engaged in the I-84 construction project.

ITD’s website states the need for the project succinctly, “The existing interstate can no longer accommodate current traffic volumes at peak periods of the day.” In addition, experts project the area, known as Treasure Valley, will experience continued growth leading to increased congestion in the corridor.

The route, which is two lanes in each direction, was built in the 1960s when the needs for the area were much different. Currently, it is at capacity, and backups and congestion are a regular occurrence.

“This section of I-84 cuts through two counties which are the fastest growing in the state as there are tons of people moving here,” says Jake Melder, a Public Information Officer for ITD. “I-84 is the backbone for transportation in the valley, so we need to expand it for safety and to relieve congestion.”

The project is part of a corridor-wide vision to add lanes and address capacity issues at a couple of interchanges. This project adds the possibility of a future addition when capacity is reached in the future.

Project Scope
The project includes multiple elements such as:
  • Widening I-84 to three lanes in each direction
  • Replacement and widening of canal, culvert, and lateral crossings
  • Replacement of one I-84 overpass (two existing bridges)
  • New noise walls
  • Adding an additional lane on two westbound off-ramps

“We’re widening the highway from two to three lanes to provide capacity and promote future growth of the highway,” says Andrew Linder, ITD’s Project Manager for the western end of the project.
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The structures that are being replaced are in acceptable condition. However, due to the widening of I-84, they will become functionally obsolete.

Two Even Sections

Five miles of I-84 are being widened. The project is split into two nearly even parts.

If the project was kept at one, it would have been the largest in the state, and there are few prepared to handle the workload it would have entailed, according to Melder. “By splitting the project into two, we increased the competitiveness and gave more contractors the ability to bid,” Melder says. Another benefit is competition tends to lead to lower bid prices.

Serving as the general contractor on the eastern project is Concrete Placing Co. Inc. They were a prime contractor on a previous section of the interstate that was expanded. Western Construction, Inc. is the prime contractor for the western part of the project. Both contractors were awarded the projects by being the lowest competitive bidder.

Because the area where the project is taking place is experiencing tremendous growth, there are multiple infrastructure projects going on in Treasure Valley. This can be a challenge.

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“We need to maintain communication and coordination on the projects in the area, so they run smoothly,” Linder says. This is especially true of the Eastern and Western Section of I-84. “We have one traffic control contractor between the two different projects, but we still have a strong need to coordinate the phasing between the two contracts,” Linder says.

As of 2019, the average daily traffic count on this section of I-84 was 60,000 vehicles and it is estimated to be 91,000 by 2045. To maintain traffic speed, there are variable speed limit signs in the work area. The speed is set based on the warranted conditions that are comfortable and safe for the traveling public and the workers out there. The variable speed system enables a responsive adjustment to the speeds as activities within the work zone allow. When construction crews are not in the work zone or when safety barricades are in place, the speed limits can be set at the traditional 65 mph. This further promotes mobility without sacrificing safety on the Interstate.

Although the traffic is significant, it’s predictable. “Our traffic pattern is very directional,” Melder says, “In the morning vehicles commute east to Boise and at night it’s reversed. One of the commitments to the public was to keep both lanes open during peak periods. Therefore, scheduling work accordingly is a challenge. In addition, hauling dirt and maneuvering construction equipment needs to be scheduled around lane closures, which can occur during off-peak times.

Another challenge is that the project is located next to Caldwell Industrial Airport. Being so close to the full-service airport requires coordination with the FAA and means additional concerns and a permitting process.

Only the Beginning
The eastern section of the project was bid out for $37.5 million. It began in this past summer and is expected to be complete during the winter of 2022. The western section was bid out for $59.3 million and also began in the summer. It is anticipated to be complete during the summer of 2023. Additional costs were paid for the right of way, design costs, and consultants to administer some of the work.

Funding for the project is coming through grant anticipation revenue vehicles of GARVEE bonds. “ITD is issuing bonds that will give us a larger sum of money than what we have on hand, and we will pay it back with federal aid,” Melder says.

The project is in its early stages, but is currently on budget and on schedule. “Keeping a project on schedule and on budget requires recognizing you can’t prefect make assumptions, so you have to deal with the changes as you encounter them,” Linder says. “It helps if you can develop relationships with the contractor and other entities involved, such as the stakeholders.” This way issues can be addressed in a timely manner, and they can be mitigated.

When construction on this section of I-84 is complete, it will accommodate the growth in the area, as well as what’s next. It will allow for the safe movement of people and goods that are coming to and through Treasure Valley.

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