More than half complete, the $90 million Idaho Transportation Department (ITD) improvement of Interstate 15, from Utah to Montana, will wrap up this summer.

"I-15 was at the end of its design life and ready for a rehabilitation effort," says Dan Harleson, ITD Project Manager for the I-15 work.

I-15 was originally constructed in the 1960s and 1970s, using a 40-year design life. Sections were deteriorating and cracked. I-15 is a major corridor, with tourists from Salt Lake City traveling north to Yellowstone Park and trucks carrying goods from the Port of Seattle to the eastern part of the country.

Construction Overview

During the projects' first year, from April until November 2017, the department spent $50 million and contractors paved 157 lane miles, repaired 11 bridges, and replaced more than 62,000 feet of guardrail. This spring, $40 million of work will commence on the remaining projects, with finish expected before the end of the year.

In a normal year, ITD spends between $5 million and $10 million on construction on I-15. Therefore, these projects represented a major investment for the department.

ITD broke the I-15 improvement work into smaller packages for ease of management and to give local contractors the opportunity to successfully bid on the work. The projects ranged from $2 million to $12 million.

The department installed Bluetooth sensors along the length of the project to monitor traffic flow and developed a smartphone app, so motorists could check travel times to avoid delays.

"People were able to plan their travel and avoid peak times," Harleson reports. "It worked OK, and we learned a lot."

Multiple Contractors

Contractors completed several projects for ITD in 2017.

Western Construction of Boise, Idaho, completed the 15.3-mile segment from Spencer to the Montana state line in late fall. The contract included work at the Stoddard Creek and Humphry interchanges, including repaving of ramps and cross streets.

HK Contractors of Idaho Falls reconstructed three ramps at the Osgood Interchange, north of Idaho Falls. The work included realigning the ramps to enhance sight distance and replacing the northbound on ramp and both southbound ramps.

The three bridges that cross I-15, north of Idaho Falls, received concrete repairs and bridge deck resurfacing by JM Concrete of Idaho Falls. The work is expected to extend the bridges' life for many years.

Knife River NW of Boise completed the 6-mile resurfacing of I-15 from the Fort Hall Reservation boundary near Pocatello to Burns Road. The project included improving clearance at five overpasses. Knife River planed to rehabilitate the Fort Hall Main Canal bridges, after the canal dried out during the winter. On this section, Knife River partnered with the Shoshone-Bannock Tribe in Fort Hall and its Tribal Employment Rights Office to provide jobs and dispatch tribal workers. Knife River trained some of the operators. "It was a good partnership," says Matt Abrams, Knife River Project Manager. Knife River also completed the 7-mile resurfacing of I-15 from Arimo to McCammon.

On the Arimo section, Knife River used cold-in-place recycling. The company milled out the top 4 inches to 6 inches, leaving 2 inches to 4 inches. The material removed was pulverized. Then cement powder and oil were added, mixed up and placed on the road. It guarantees a good base and increased the lifespan of the road. 

"It was a good experience," Harleson says. "It's milled, processed and put back down, all in one process. It saves on resources. You can use 100 percent of the mix. It's resource and energy efficient."

Cold-in-place recycling also reduces the chances of cracking, since it is more flexible and forgiving, Harleson says.

Abrams reports that it takes more time than a mill and replace, because of the limitations of the production with the cold-in-place train. Knife River used GPS to lay out the horizontal limits of the recycling and center line.

"The cold-in place process went very well and was successful," Abrams says. 

Harleson agrees, saying, "Knife River did an outstanding job."

DL Beck of Rexburg, Idaho, completed work to preserve the Pocatello Bridges, made repairs and prevented deterioration.

Throughout construction, one lane of traffic was maintained in each direction, with speed limits reduced. Interchange ramps and shoulders were closed occasionally.

Among the work to take place this year is ballast reconstruction near the Montana state line, the Rose Road interchange, reconstruction of the interstate from McCammon to Inkom, and the Arimo to McCammon Bridges.

The Eclipse Changes Schedules

Due to the solar eclipse in August, the department shut a couple of projects down early, so the road could completely reopen to traffic to accommodate estimates of significant additional traffic. The total eclipse was visible about 50 miles north of the project.

"We had a lot of people coming up from Salt Lake City to see the eclipse," Harleson recalls. "Even with both lanes open, a trip that normally takes an hour was lasting four or five hours. There was so much traffic."

Knife River accelerated the first phase and then shut down and pulled the equipment for a week during the eclipse. The company completed both sides of the project in 2017.

Jack B. Parson of Boise holds the contract for the 3.6-mile resurfacing of I-15 from Sand Road to the South Blackfoot interchange. The company delayed the start of its project to accommodate eclipse traffic and completed work on the southbound lanes in 2017. The work includes replacing 9.6 inches of cracked pavement and soft spots under the surface, and increasing vertical clearance under three overpasses.

HK Contractors worked with JB Parsons to rehabilitate 4 miles of interstate south of Blackfoot. The start of this project was delayed to avoid interfering with eclipse traffic. One direction of the interstate was completed in 2017 and the other side will be completed in 2018.

"It was a lot of work in a short period of time, and it off went smoothly," Harleson says. "And we accommodated the eclipse."