Plagued by rock slides, rising costs, Idaho 55 project fraught with risks from outset

·21 min read

The ongoing Idaho 55 highway project near Smiths Ferry will cost more than double the original price tag after repeated rock slides demonstrated that its initial design and construction plans were unsafe, state transportation records show.

The mile-long stretch punctuated by granite hillsides along the Payette River is a key connection between Boise and McCall, and has suffered at least six slides during the first two years of construction to widen and straighten the roadway. ITD deemed half of those slides “significant,” while the three others were not previously made public by the state’s transportation agency, the documents obtained in an Idaho Statesman investigation revealed.

Two of those undisclosed slides happened at a location on the road that later slid a third time. That third slide, in January, forced the highway’s closure for two days while crews and technical experts reviewed the stability of the hillside. Two months earlier, a different rock face within the project site let go of a much larger slide, closing the road for nearly three weeks, and ultimately raising questions about public safety all the way up to Gov. Brad Little.

Records obtained by the Statesman under the Idaho Public Records Act illustrate an active campaign by Idaho Transportation Department officials to positively message potential safety issues and strike confidence in the thousands of commuters who continued to drive the section of highway each day. That included spending $500,000 on public relations for the project.

Yet, behind the scenes, the agency already started to see warning signs early into construction. It turned out that the original design plans were not sufficient to avoid such rock slides in the extremely challenging and highly sensitive terrain.

“The adjustments we have made in the field acknowledge how much we put a premium on safety,” Vince Trimboli, an ITD spokesperson, told the Statesman during a June visit to the project site. “We want to make sure this road is as safe as possible. And so in the name of ensuring the safety of the traveling public, yeah, we had to spend more money.”

Since fall 2020, motorists have been limited to a single lane of travel through a project on Idaho 55 north of Smiths Ferry. The highway project is on schedule to be completed by fall 2022 despite a series of slides that shut down the road while crews removed the rockfall.
Since fall 2020, motorists have been limited to a single lane of travel through a project on Idaho 55 north of Smiths Ferry. The highway project is on schedule to be completed by fall 2022 despite a series of slides that shut down the road while crews removed the rockfall.

The repeat rock slides triggered internal reviews by ITD, which is tasked with delivering the highway upgrades by this fall, and led to large-scale design changes that have pushed the total cost of the high-profile project to as much as $45 million. Agency estimates just three years ago put the cost of construction at about $19 million, records showed.

BoiseDev was first to report about safety concerns on the Idaho 55 road-widening project.

Construction involves blasting and removing portions of nine rock faces on the west side of the project site. Work began in September 2020, but crews determined within that month that at least one of the hillsides set to be pushed back to widen the road consisted of much different material than assumed in the design plans.

Seven months into the project, after a March 2021 rock slide closed the highway for more than a week, ITD chose to change course.

The agency decided to tap McMillen Jacobs Associates, a Boise-based engineering firm already involved in the project on a more limited basis, to review the design and construction plans in their entirety. Their analysis resulted in revising the planned slope of the nine rock faces, with the expanded contract costing an additional $1 million, ITD said.

“They’re the national experts, they used advanced techniques,” Alex Deduck, ITD’s project manager for the Idaho 55 highway widening, told the Statesman during the site visit. “You know, it costs money, but, man, they’re the best. And they go above and beyond to make sure the project is safe, and it’s done well.”

Even with the added help and expertise — and expense — more challenges would soon come crashing down.

Between a rock and a river

Idaho 55 spans nearly 150 miles in Southwest Idaho, traversing six counties from west of Boise near Marsing and stretching north past McCall to New Meadows. Along its path, the highway links up with the Payette River south of Horseshoe Bend, and follows the route of the Snake River tributary to the southern tip of Valley County.

It’s roughly here that the roadway runs head-on into the Idaho Batholith, an expansive granite range that’s some 80 million years old. The plutonic outcropping is characterized by a series of faults where the rock has space to shift, periodically hurling hunks of granite downhill — including onto established transportation corridors below.

In other words, the mountainous area is fraught with geographical obstacles, including occasional seismic activity. It is less than ideal for a road, state officials have acknowledged.

“It’s quite a dramatic landscape … and a hazard in terms of the stability of the slopes and the rocky outcrops,” said Claudio Berti, state geologist and director of the Idaho Geological Survey. “It’s a very, very challenging stretch of the road, and I pity the people who have to work with it.”

Nonetheless, the north-south roadway originally known as the Payette Highway was carved into the rugged topography, and dates to at least the 1920s, according to the U.S. Forest Service. The nearby Rainbow Bridge was built in 1933 to guide drivers to opposite sides of the river.

For decades, ITD sought to address the narrow, curvy 1-mile section of Idaho 55 through the canyon north of Smiths Ferry, which has a 33% higher rate of vehicle crashes compared with similar roads across the state, according to a traffic report during the conceptual design phase. Through 2021, this single mile of Idaho 55 that ITD officials call the “white-knuckle section” had 154 crashes over the past 20 years, agency data showed.

“This road, in the best of conditions, is sketchy,” Deduck said. “And, in the worst conditions in the winter, is scary to drive because you don’t know, if something happens, if you’re going to go in the river.”

More than half of those crashes during the past two decades involved injuries. One involved death. In June 2017, a Garden City couple in their 70s drowned when their SUV went down the embankment and into the river.

During early planning stages, ITD explored dozens of highway alternatives. But based on a variety of logistical, financial and environmental factors, the agency pursued the current project.

“There was talk of a bypass, but that probably could have been three to five times the cost of this,” Trimboli said. “And this seemed like the most logical choice — to improve this stretch, and make it safer for drivers.”

Vince Trimboli, an Idaho Transportation Department spokesperson, explains the process of cutting into rock with Alex Deduck, ITD project manager, during a tour of the mile-long stretch of Idaho Highway 55 north of Smiths Ferry.
Vince Trimboli, an Idaho Transportation Department spokesperson, explains the process of cutting into rock with Alex Deduck, ITD project manager, during a tour of the mile-long stretch of Idaho Highway 55 north of Smiths Ferry.

Before construction, the road featured a tight squeeze between the river and the rock faces on the southbound side, permitting just a single lane in each direction and a sporadic shoulder on the northbound side. Where there’s no shoulder, guardrail or cement dividers help prevent vehicles from going off the highway into the river. But limited sightlines around the bends in the road can make the path difficult to navigate, especially at night.

Once finished, the project will temper some of the curves, add guardrail and shoulders for both lanes, as well as pullouts and a ditch below the hillsides to catch gravel and boulders that still spring loose. It also will soften angles of the nine rock faces, and a variety of other safety enhancements will reduce the chance of rocks landing on the road and affecting traffic.

“Our goal with this project is to enhance the safety of this mile-long section of the roadway,” Deduck said in an August 2020 news release, just ahead of the project’s start. “Construction crews will remove about 146,000 tons of rock from the hillside, which we want to do very carefully to not create rock slides or impact the river.”

As crews worked toward completing the three-year highway project, though, the process proved anything but smooth.

Early changes to project design

Less than a month into the project, workers found they couldn’t execute the full construction plan developed by engineering firms Forsgren Associates and American Geotechnics, each headquartered in Idaho. In-field adjustments were needed on at least one of the rock faces. Such practices, which were identified in the construction plans, are common in road projects, according to engineering experts.

The two firms’ initial design, in collaboration with ITD, included recommendations that would maintain slope stability of the granite hillsides while widening the road. Their assumptions were based on data and analysis of the rock that make up the hillsides above the highway, ITD officials said. Modeling showed that 76-degree angled slopes, in some cases in conjunction with other safety enhancements that included steel mesh draped down the rock faces, would be secure.

“When we did our design, we could see the exposed rock face, but we couldn’t see 100 feet into the hillside,” Steve Waldinger, a vice president and division manager at Forsgren, who worked as the Idaho 55 project’s design engineer, told the Statesman by video interview. “We made our best engineering judgment with the information we had on what slope we needed to cut that back to, but knowing, if during construction, if they hit a crappy area and a bunch of decomposed granite, adjustments were expected.”

Several regional experts declined to comment to the Statesman about the Idaho 55 project, citing other work for ITD and possible conflicts with the national engineers’ code of ethics.

Deeper excavation by crews with M.A. DeAtley, a Washington-based construction firm that bid the project at $25.7 million, discovered that one of the northernmost rock faces — Cut 8, as it’s known among the nine hillsides within the project — was not, in fact, composed of solid rock. The material was still granite but “highly weathered,” said Jason Brinkman, ITD’s engineering manager for the southwest region that includes Valley County.

“This rock was so soft, you could crush it with your hands and it would turn to dust,” he told the Statesman by phone. “So in less technical language, we found nothing but dirt because the rock is so weathered.”

Crews work to remove rock and debris from one of nine cuts along the Idaho 55 highway project north of Smiths Ferry. Construction began in fall 2020 to widen and straighten the mile-long stretch of road for safer travel along the Payette River.
Crews work to remove rock and debris from one of nine cuts along the Idaho 55 highway project north of Smiths Ferry. Construction began in fall 2020 to widen and straighten the mile-long stretch of road for safer travel along the Payette River.

ITD talked with its contractors, including McMillen Jacobs working then only as the project’s blasting consultant, and decided to flatten Cut 8’s slope down to 45 degrees to achieve greater stability. That meant removing and trucking out a lot more rock.

In an internal Cut 8 report sent to Brinkman in October 2020, ITD geotechnical engineer Dave Richards wrote that it was “evident” that the initial design’s plan calling for a pinned vertical mesh — a safety enhancement on the rock face to limit slides — was “problematic” because the location sat on a known fault line, which made the rock “difficult to stabilize.” He instead affirmed the group’s new plan to lower the angle of the rock face.

“A flat slope minimizes the number of launch points that will cause rocks to bounce,” Richards reported, of potential rockfall into the roadway. “Because the (45-degree) slope will consist of broken rock and soil, it should be extremely stable.”

Construction wrapped up for the winter the week before Thanksgiving, with crews remobilizing four months later in spring 2021. That’s when the project experienced its first rock slide — which officials labeled a “big one.”

First slide foreshadows more ahead

On the first day of construction restarting on Idaho 55 in mid-March 2021, a rock slide occurred at about 10 p.m. at a granite spire on the project’s northernmost rock face, known as Cut 9. Large boulders fell onto the heavy construction excavators directly below but did not land on the road, according to emails between ITD officials.

Two hours later, rocks continued to fall from the slide, leading to the highway’s emergency closure and ITD’s public alert. Several small earthquakes also took place in the area over the three days prior to the Cut 9 slide, though ITD officials do not think they were the cause.

Berti, the state geologist, said the temblors may have played a role in the slide, but added that it would require more analysis and agreed that it is unlikely.

“I don’t think that there is obvious causality for that,” he told the Statesman. “They may have been a contributing factor. The likelihood of that is pretty small, but it’s hard to prove. We don’t know, exactly.”

ITD officials also maintain that blasting work to remove rock from the slopes was not the cause of the slide, nor any of those that would follow. Instead, on Cut 9, they blamed spring runoff within the hillside that melted and loosened rock blasted by crews the prior fall.

“We attribute it to warm temperatures early on in the spring of 2021,” Deduck said. “That accelerated the snowmelt and infiltrated the ground.”

Not quite a week later, Cut 5, a rock face toward the southern end of the project also slid, but was small and didn’t reach the roadway, ITD said. The agency chose not to notify the public because it didn’t require closing the highway, nor was it a threat to safety, ITD officials said.

“It’s somewhat typical, when you’re excavating, that things come down,” Deduck said. “I’d be surprised if the public even noticed if it happened. We didn’t let anyone know, honestly, more so just because it’s just normal construction operations. It certainly did happen, but never posed a problem to the traveling public.”

Alex Deduck, Idaho Transportation Department project manager, thumbs through a stack of design and construction plans for the mile-long stretch of Idaho 55 north of Smiths Ferry.
Alex Deduck, Idaho Transportation Department project manager, thumbs through a stack of design and construction plans for the mile-long stretch of Idaho 55 north of Smiths Ferry.

As crews continued that second construction season to make adjustments to several of the hillsides, Deduck exchanged an email with Richards. In it, he questioned the depth of the project’s geotechnical investigation of the rock faces, which was the basis for the initial design plans.

“It seems for this project the structural integrity of the rock was never looked at,” Deduck wrote in the April 5, 2021 email. “Our pinned mesh anchors would not have sufficed and slides similar to (Cuts) 9 and 5 would continue to happen.”

Richards, in an email to his ITD supervisors nine months later, also offered his professional opinion that the initial design plans “relied too heavily on the pinned mesh to mitigate all the problems.” He questioned how the project design could adequately consider appropriate safety enhancements “without knowing what the exposed rock faces were going to look like.”

“Trying to design rockfall mitigation on what you think might be there is near impossible,” he wrote in the January 2022 email obtained by the Statesman.

Last week, Brinkman downplayed Richards’ role and understanding of the project. He said the email in which Richards shared his opinions lacked “proper characterizations of how things work,” was “not particularly informed,” and came a week before Richards retired from ITD.

Richards did not respond to multiple requests from the Statesman for comment about his involvement in the Idaho 55 highway project.

Brinkman and Deduck also walked back Deduck’s emailed comments, labeling them “a little bit of hyperbole” under the pressures of the project’s first slides, and in the middle of having to problem-solve and find solutions in the moment.

Deduck said such levels of geotechnical investigation, including rock drilling, would have been “very expensive,” while Brinkman highlighted the other analyses conducted by Forsgren and American Geotechnics. He called greater review of the rocks “not particularly effective” for this type of project, if it even could have been done given the geography.

“It’s not feasible to do,” Brinkman said. “You’d have to clear the forest, excavate paths, bulldoze to get to the slopes — on property we didn’t even own yet — just to drill slopes to see what you might learn. While we do that type of drilling for things like investigating bridges or what’s under a road, it’s basically not done for this type of cut slopes.”

Stan Crawforth of American Geotechnics (now Shannon & Wilson, Inc.), who worked as the firm’s lead geotechnical engineer on the Idaho 55 highway project, declined an interview request.

“We did as much investigation as we could,” said Forsgren’s Waldinger, the project’s design engineer. “There are so many variables. It’s easy to know how to fix it when you can see it. And it’s part of why the plans called for having a blasting consultant up there, because we didn’t know what was behind the rock.”

‘True anomaly’ among three slides in one week

After seven months passed, overnight as crews again prepped for a winter pause of construction in early November 2021, a rock slide occurred on Cut 2, one of the southernmost rock faces — as did a second one on Cut 5 — according to emails between ITD officials and project contractors. Again, the agency chose not to tell the public because it didn’t require a closure, and they believed it posed no danger to the motorists, agency officials told the Statesman.

On the advice of an engineering geologist with McMillen Jacobs, the fallen rock was to be left at the base of Cut 5’s slope over the winter “to avoid similar failure of the unreinforced section.” ITD and crews then planned to address that rock face in spring 2022, when “we can better stabilize the area,” Deduck replied in an email.

Nine days later, on Nov. 18, 2021, in spite of the revised plans and blasting of Cut 8 to a 45-degree angle, the slope suddenly gave way around 2 p.m., spilling nearly a football field in length of rock and debris into the center lane. The slide amounted to upwards of 50,000 cubic yards of material — equivalent to several thousand large flatbed truckloads — that needed to be moved to reopen the road.

Once more, however, ITD reported no injuries. But the slide came within a couple hundred feet of a worker driving a vehicle used to guide traffic through the alternating one-lane construction site, ITD said. The road had moments earlier reopened from a planned four-hour afternoon closure for construction, and the worker was leading the first line of motorists through the area.

The slow pace of the slide allowed workers on the construction site to react and avoid the rockfall, Trimboli said.

“We kind of call it the molasses slide,” he said. “They saw it, they stopped, they turned traffic around and got them out and we closed the road.”

ITD officials have repeatedly said that when they knew of any risk to the public, they closed the road.

The near-miss of the worker did not require ITD, nor its contractors, to report the incident to the Occupational Safety and Health Administration, Mike Petersen, a spokesperson for the U.S. Department of Labor, told the Statesman.

OSHA also later followed up with M.A. DeAtley about the Idaho 55 project, likely because of a Statesman inquiry after a subsequent slide, Petersen said. He was unaware of any other media outlets contacting the agency at that time. In that review, OSHA signed off on the requested report from the company about their safety protocols on the project site.

Motorists have routinely been delayed while traveling on Idaho 55 north of Smiths Ferry since fall 2020. The project to widen and straighten the mile-long stretch of highway to create a safer corridor is on schedule to be finished this fall.
Motorists have routinely been delayed while traveling on Idaho 55 north of Smiths Ferry since fall 2020. The project to widen and straighten the mile-long stretch of highway to create a safer corridor is on schedule to be finished this fall.

Meanwhile, Atlas Strategic Communications, a public relations firm based in Boise that ITD hired to help issue information about the project, began to develop messaging around the November rock slide. An official with Brundage Mountain Resort pressed ITD to release more details to reassure the public that the road would be safe to drive once it reopened.

“So far, she is the only stakeholder that is expressing concern,” Erin Hudson with Atlas wrote in an email to ITD officials. “But I want to make sure we get her a detailed reply before any rumors start spinning up.”

The operation to reopen the road took almost three weeks to complete, in addition to stabilizing the hillside so traffic — including skiers headed to and from McCall in the winter — could return. Crews finally got the canyon reopened on Dec. 6, but now ITD unexpectedly had to devise a new plan for Cut 8 because of what Deduck described as a complex, clay-like layer deep inside the slope. He said ITD had no prior knowledge of the layer.

“That landslide was a true anomaly, and would have happened no matter what,” Deduck said. “In the world of slope stabilization, (45 degrees) is pretty stable. So to have something fail … and at such a low angle really caught everyone off-guard.”

Eventually, the group decided to flatten Cut 8 even more, down to a 32-degree angle slope to prevent future slides at the rock face. Construction crews are at work to finish it this year, which will ultimately mean pulling another 100,000 cubic yards from that slope alone.

For comparison, on the whole Idaho 55 project, ITD initially expected to take 140,000 cubic yards of rock from the hillsides, or what equates to more than 11,000 truckloads. Later, after McMillen Jacobs’ review of the project, the firm recommended dropping most of the nine rock faces to 63-degree slopes, which entailed removing another 100,000 cubic yards from the project site.

In total, 340,000 cubic yards, or more than 27,000 truckloads, are now set to be removed from the nine rock faces. That comes at a considerable cost covered by an ITD Board approval in April to provide almost $14.5 million more in state and federal funds for the project, raising the total cost of the project to upwards of $45 million.

“Gov. Little has said he is always concerned whenever a state agency project goes over budget,” Madison Hardy, Little’s spokesperson, said in a statement to the Statesman. “The governor’s office has requested an ITD cost analysis of the project to better understand the factors that have led to the increased cost projections.”

‘Here we go again’

About a week after crews reopened Idaho 55 near Smiths Ferry, construction again halted for the winter. But they were forced back out to the roadway toward the end of January after yet another slide.

Around 10 p.m. on Jan. 22, the slope on Cut 5 let loose for the third time since construction began on the project, violently spewing a mix of snow and rock straight downward. Most of the debris landed in the ditch below, but about a foot of snow landed on the road, while a large boulder stopped in the northbound lane and a smaller rock ended up near the river, ITD records showed.

By then, the Statesman had begun looking into the Idaho 55 road-widening, and just two days earlier submitted its first public records request to ITD seeking details about the project and its past rock slides.

“Here we go again … We had another rock fall on Smiths Ferry!” Brinkman wrote in an early morning Jan. 23 email to colleagues and project contractors. “We need to fill in the (communications) team on handling broader messaging. … If anyone needs any motivation, the McCall Winter Carnival is next weekend, and we already have an open media public records request about rock slopes, so this will be of interest.”

Crews worked the next day to stabilize the hillside and the highway reopened to traffic within two days. The prior two slides on Cut 5 received no mention in an ITD news release at the time.

“The Idaho Transportation Department is aware of the risks in this slope,” the ITD release read. “A team of geotechnical experts inspected the work and confirmed it is safe to reopen the highway to the traveling public.”

In early February, construction crews positioned shipping containers at the base of the troublesome rock face as a “safety barrier between the hillside and the traveling public,” ITD said at the time in an Idaho 55 project update. An ITD spokesperson later told the Statesman no additional slides happened over the spring.

At the end of June, BoiseDev reported about potential safety issues within the project, and the increasing costs to the state to finish the highway upgrades. Gov. Little and his office responded with surprise, demanding a detailed report from ITD within 24 hours.

ITD responded to the governor’s request with an 18-page report that included assurances from top officials working on the Idaho 55 project that the roadway remained safe. Little and his office appeared satisfied, choosing not to seek a second opinion from a third-party expert on the project’s safety.

In a written statement last month, Hardy noted that experts at ITD reiterated in their report that road closures or other mitigation strategies were unwarranted.

“There are inherent risks in traveling any mountain road in Idaho,” Hardy said. “Gov. Little encourages Idahoans to use caution traveling on any roadway in order to keep themselves and their loved ones safe.”

The 1-mile project on Idaho 55 remains on track for its originally scheduled finish this fall, ITD said. Eight of the nine sloped hillsides are today “substantially complete,” as work primarily continues to wrap up rock removal from Cut 8.

“We, sitting here today, feel comfortable with where we’ve gotten with this. I don’t know any way we would have gotten that level of knowledge in advance,” Brinkman said. “What I do sleep well knowing is, as of now, this will be one of the safest sections of highway on (Idaho) 55. It’s well-engineered, well-sloped and well-secured, at this point.”