Member Login

ITD’s Smiths Ferry Idaho 55 project won’t be done on time and price tag continues to increase

The price tag for a years-long project to widen a curvy section of Idaho Highway 55 near Smiths Ferry has increased again, this time to a potential maximum of more than $60 million. 

A report produced by the Idaho Transportation Department for Governor Brad Little in early August shows how unexpected conditions at the worksite and a series of landslides led to significant cost hikes on the project during construction. The project, which was first estimated to cost $18.9 million in September 2019, has now potentially tripled in price to a range between $52 and $62 million. 

ITD also told Little in the report the project will not be completed until Spring of 2023, instead of this fall as the agency originally told multiple media outlets earlier this year. Agency spokesperson John Tomlinson told BoiseDev in an email that the final work expected to be completed next spring includes erosion control, slope drainage, and stabilization on the slopes of the canyon walls. He didn’t specify if travel will still be restricted to one lane into next spring, but he said the first layer of asphalt on the highway is expected to be laid by the end of the month. 

The Idaho Statesman first reported the delay.

“Crews will work as long as weather permits this season, which typically is suspended for winter from December-February,” Tomlinson wrote. “The contractor is motivated to finish as much work as possible this fall, and at this time, will have a better idea of what else needs to be completed in Spring 2023.”

This report to Little comes after an investigation from BoiseDev earlier this summer detailed the cost hikes on the project, warnings signs of unstable slopes along the highway, and concerns from an internal geotechnical engineer about the project. 

Little’s Press Secretary Madison Hardy did not respond to a request for comment on the cost overruns on Highway 55. 

Landslides main source of price increases 

The costs to widen and straighten the curves along the mile-long stretch near Howard’s Plunge have been climbing for years, but ITD says the landslides in the area ended up being a significant contributor to the cost increase. 

A preliminary cost estimate in May of 2016 estimated the project cost to be roughly $12.6 million, according to a Location and/or Design Study Report prepared by design firm Forsgren Associates. BoiseDev obtained the document in response to a public records request, along with dozens of other documents following the publication of our initial investigation. This rose to a final engineer’s estimate of $18.9 million by September 2019. 

The lowest bid on the project was from Clarkston-based contractor M.A. Deatley for $25.7 million. Once you added in the extra construction costs, like contractors for engineering design, public relations, relocating utilities, and purchasing right-of-way for the project, the total project budget was $30.8 million when ITD gave the project the green light to start in the fall of 2020. 

As BoiseDev first reported earlier this year, conditions at the worksite required ITD to reevaluate its project design after the first of three major landslides hit the project in March 2021. This was when the state brought outside engineering firm McMillen Jacobs in to consult on the project after the hillside at Cut 9 at the project’s northernmost edge slid onto the highway.

A view of the base of Cut 8. Photo: Margaret Carmel/BoiseDev

The redesign, which required another 100,000 cubic feet of excavation, added $6.8 million to the project.

The biggest cost to the project came in November when a large landslide struck at Cut 8, dumping hundreds of thousands of cubic yards onto the highway and closing it for several weeks. Earlier this year, ITD told BoiseDev did not have a cost estimate for how much the cleanup of the slide, additional excavation, or redesign of the slope to a 45-degree angle cost, but in its recent cost analysis submitted to Little the agency said this landslide added another $9 million to the project price tag. This brought the cost of the whole project as of April 2022 to $46.6 million. 

Tomlinson said the landslide at Cut 8, which the agency called “unforeseen,” is the primary culprit for the project being over budget. And on top of the cost of cleaning up the landslide, the agency could spend another $5-$15 million more on stabilizing the slope, bringing the cost possibly up to $62 million. The ITD board will have a more specific update at its September meeting. 

“These supplemental funds would not be needed if not for the landslide repair and permanent stabilization,” Tomlinson wrote in his email. “Had the initial designs and analysis from 2017 – 2019 revealed what was uncovered after work had started, the request for budget for the project would have likely arrived at a similar budgeted amount.”

Speed limits dropped during design due to ‘difficult’ terrain

The speed you can drive on a curvy mountain highway isn’t determined on a whim. 

Different speed limits have corresponding types of curves they can be applied to, with the sharpest curves requiring the lowest speed limit. The flatter the curve, the faster the speed limit can be to keep drivers safe. And in the mountains, a flatter curve means more excavation.

The Location and/or Design Study Report developed by Forsgren Associates notes the original charter for the project envisioned a road straight and wide enough for a 55-mile-per-hour speed limit with passing lanes through the area south of Smiths Ferry. This changed in 2015 when ITD officials discussed alternatives for the project that “increased the safety of the roadway while staying within the budget.”

“Due to the difficult mountainous terrain of the project area, a 45 mph design speed was used,” the report says. This is an increase from the 30-35 miles per hour speed limit this stretch had before construction.

The study report says early designs by 2016 found ITD would need to realign the road through the construction area to flatten the curves and add retaining walls to make room for guardrails and other safety features the agency wanted to implement on the windy stretch of highway. In response to this design change from ITD, Forsgren put together a report estimating how much it would cost, comparing how much it would cost to build a roadway for several different speed limits. 

Highway 55 Smith's Ferry
Photo courtesy Idaho Transportation Dept.

This report notes particular challenges in the northernmost section of the project due to fault lines cutting through the area and springs carrying water through the rock. This is also where officials noted signs of instability during the first half of 2021, and the first two significant landslides occurred, at rock cuts 8 and 9, respectively. 

Forsgren’s report noted that if ITD designed a road through this area with curves flat enough for a 45-mile-per-hour speed limit, the road would require so much excavation that it would have “a high cost with unknown impacts for the benefit of increasing the curve speed.” In response to the conditions in the area, ITD opted to design those northern curves to have a 40 mph speed limit. 

“The section (of the report) you referenced points out the due diligence given to the challenges of balancing design speeds in this area with significant geographical constraints,” Tomlinson wrote to BoiseDev. “…The project reduced the design speed to 40 mph for the 5 northern curves to incorporate practical design that is environmentally and context sensitive.”

No longer the cheapest option

Even when ITD finishes work on the highway next spring, there is still more to do. 

The next phase of the project includes building a replacement for the historic Rainbow Bridge travelers currently use to cross the Payette River just north of the Smiths Ferry project. The new bridge is planned for the stretch next to the existing bridge, which will be kept as a scenic lookout. 

The project is still in its early design and scoping phases, but it is currently planned for the 2028-2029 fiscal year. Right now, its estimated price tag is $22.3 million, bringing the total price tag for the work on the highway to an estimated over $80 million by the time the bridge is complete assuming the project does not substantially increase in price in the next seven years. 

A photo of the Rainbow Bridge dating back to the early 20th century. Courtesy of the Idaho Historical Society

ITD analyzed over 25 possible routes for the work on the highway in the early 2000s before finally settling on expanding the highway through the canyon in 2008, according to BoiseDev’s reporting earlier this year. This route was selected because it had the least environmental impact, didn’t require eminent domain to take any private residential properties, and was the cheapest choice at the time. 

The current project was bid at $25.6 million. All alternates would have cost at least double that. In 2008 the second listed alternate route would have cost about $68 million to construct, the third would have cost around $59 million and the final route was estimated to cost about $66 million.

The maximum cost of the project in progress and future reroute around Rainbow Bridge totalling $80 million is significantly more than the 2008 estimate. But the other routes also could have seen costs rise.

When asked if the path going through the canyon was still the most cost-effective option compared to going around after all of the cost overruns and the added price tag for replacing the Rainbow Bridge, Tomlinson said the agency stands by its decision. 

“ITD is confident in the analysis and in the process to arrive at the decision for these projects,” Tomlinson wrote. 

More to read

Margaret Carmel - BoiseDev Sr. Reporter
Margaret Carmel - BoiseDev Sr. Reporter
Margaret Carmel is a BoiseDev reporter focused on the City of Boise, housing, homelessness and growth. Contact her at [email protected] or by phone at (757)705-8066.

Top Recent Stories