Each year since 2016, Idaho has ranked first or second in the country for fastest population growth. From 2019 to 2020, the Idaho Business Review reported that the state had the largest single-year population increase in the U.S., growing 2.1%, to 1.8 million residents.

Many of the new arrivals have found homes in the state’s northern panhandle, known for its forests and small towns like Sandpoint and Coeur d’Alene, located on the shores of the large mountain lakes.

Between the increase in residents and the Spokane, Wash., metro area just 30 miles to the west, traffic in the area also has increased significantly in recent years, according to Joseph Sprague, staff engineer for District One of the Idaho Transportation Dept. (ITD). 

“The Coeur d’Alene metro area has been one of the fastest-growing parts of a fast-growing state,” Sprague says. “This corridor was identified years ago as one that needed expanding, and we’ve done a lot of projects here in the last decade.”

The department is currently in the midst of what Sprague says will be the final series of improvements along U.S. 95 and adjacent connecting routes Garwood Road and Idaho State Road 53.

The two improvement projects, with a total cost of approximately $55 million, include realignments of a section known as Old Highway 95, replacement of two at-grade railroad crossings with overpasses, a new traffic roundabout and the first single-point urban interchange (SPUI) in the region. SPUIs are similar to diamond interchanges, improving flow by directing opposing left turns onto major roadways and sometimes allowing traffic to proceed straight through from the off ramp to the on ramp. They are used more often in urban areas than rural ones.

Rusty Leahy, lead design engineer with Portland, Ore.-based David Evans and Associates, says the SPUI on U.S. 95 and ID 53 and the new overpasses should improve safety and speed on the highway. “Those were the last at-grade intersections north of Coeur d’Alene. Now you can go all the way to Sandpoint at higher speed,” he says.

“At-grade rail crossings are always a safety concern,” says Sprague. “And having the bridge on ID 53 [that connects to the new SPUI] will keep traffic from backing up into the SPUI when there is a train. All these improvements work together.”

Evolution of a Solution

“This started as just a replacement of the state road 53 bridge over the railroad,” Sprague says. “We knew that at some point in the unknown future we were going to be building an interchange at 53 and U.S. 95; we just didn’t have the funding at the time.”

Sprague says while designs were underway for the bridge, engineers were working with expectations of a future intersection. “It was all very conceptual at that point, but that was when we chose the SPUI as the preferred interchange type,” he says.

In 2017, the Idaho legislature authorized $300 million in Grant Anticipation Revenue Vehicles, or GARVEE bonds, to complete key projects around the state. “Once we got that funding, we were able to add everything, the bridges, the SPUI, and design and build it all at once,” Sprague says.

Pandemic Highs and Lows

Seattle-based Scarcella Brothers Inc. was selected as the general contractor on a design-bid-build contract for the new bridge on ID 53, the new SPUI and roundabout. Construction on Phase 1 of the project began in July 2019.

Coordinating with crews at Union Pacific, Scarcella Brothers demolished an older bridge north of the site for the new overpass on ID 53. Scarcella Brothers project manager Mike Bolster says a source of granular fill needed for the site was located directly adjacent to it on property owned by ITD.

“We had to clear the area, as it was all forested, but then we could use that as a source for the 525,400 cubic yards of granular fill we needed,” Bolster says.  A concrete crossing area was installed to allow trucks to drive over the railroad tracks and deliver material directly to the site.

Plans called for a temporary widening of ID 53 to accommodate two lanes of traffic, one eastbound and one westbound, during construction. Bolster says the contractor saw an opportunity to speed up the project and submitted a change order in September 2020. Scarcella Brothers would maintain just one lane of traffic, controlled by flaggers, and work 24-hour shifts for five days to complete the connector.

Bolster notes that the impacts to traffic were minimal because many area residents were aware of the construction and took alternate routes.

“The change saved $240,894 and cut two weeks off the schedule,” Bolster says. It also earned the contractor a Gold Award for Excellence in Construction Partnering from ITD.

While the contractor was able to find time- and money-saving changes for the project, the COVID-19 pandemic created delays beyond the team’s control, Bolster says. “There was a delay in the production of the traffic and lighting poles for the SPUI,” he says. “The delay pushed the opening of the new interchange out until November.”

Paving work on Pope Road, which heads north out of the new roundabout, was put on hold when the asphalt contractor shut down operations for the winter. “The remaining work will be completed when the weather warms up this season,” Bolster says.

One More Bridge to Cross

Phase 2 of the project—construction of a new bridge over the railroad on Garwood Road, just north of the Phase 1 projects—is currently underway, according to John Wilfong, project manager for Apollo Inc., the Phase 2 project’s general contractor, based in Kennewick, Wash.

“We are just getting started with the bridge substructure, the piers and abutments,” Wilfong says. The cast-in-place bridge will span 450 ft over the railroad tracks. He says crews have had to relocate a large number of utilities on the site.

“We’ve got buried and overhead lines, electrical, gas, communications that all have to be rerouted,” he says. “Getting permission from all of them and coordinating with the railroad is a challenge on this job.”

The bridge on Garwood and the remaining work on the two projects is expected to be complete this fall.