Rockslide on ID-55 near Smiths Ferry

Rocks Hit highway

Final Update: 9:45 a.m. 4/9/2021

Debrief of slide and slope stability

In the wake of a rockslide on March 15 along Idaho State Highway 55 near Smiths Ferry, the Idaho Transportation Department has determined the slide was a localized event and, after additional mitigation, the greater hillside remains stable.

The slide occurred within a work zone where crews are cutting into the adjacent hillside to create extra room for ID-55 and enhance the overall safety of the road. The space will be used to reduce the severity of curves, construct wider shoulders, and add guardrail and pullouts.

Water from melting snow seeped into and destabilized the hillside at a cut crews created last fall. To prevent future localized slides, ITD is enhancing the reinforcement of the hillside as cuts are created. The Department has hired geotechnical experts to aid in this effort. This approach is expected to improve reliability of the hillside’s stability and the overall efficiency of the blasting work.

“Safety is the top priority of the Idaho Transportation Department. We are thankful no one was hurt during the rockslide activity on State Highway 55 last month,” said District 3 Administrator Caleb Lakey. “Hillsides and slopes become more unstable when doing work of this nature. We expect rock fall as a part of these projects. We had precautions in place to protect the traveling public in case of any slide activity and are doubling down on those precautions.”

ID-55 is now open to a single lane of alternating one-way traffic. Travelers should plan for a fifteen-minute delay at the project location. From now until late May, there will be daily closures Monday through Thursday from 10 a.m. – 2 p.m. to allow blasting and debris removal activity.

“I appreciate the public’s patience as we responded to this rockslide,” said Lakey. “We did not take the reduction of service on this critical corridor lightly. It’s a good reminder to drive attentive and be on the lookout for rocks on the roadway during the springtime.”

The project is anticipated to continue through Fall 2022. For more information, visit ITDprojects.org/id55smithsferry/

update #12: 6:00 a.m. 4/2/2021

Spring Construction Schedule Resumes Today!

ID-55 is open to one lane of alternating traffic between Smiths Ferry and Rainbow Bridge starting at 8 a.m. today. Drivers can expect full road closures Monday-Thursday from 10 a.m. to 2 p.m. and one-way alternating traffic with a 15-minute delay when the road is not closed.

To sign up for email updates and text alerts, visit itdprojects.org/ID55smithsferry.

update #11: 3:50 p.m. 3/31/2021

Idaho Highway 55 near Smiths Ferry will reopen to the public beginning at 8 a.m. Friday morning to a one-lane alternating traffic configuration. The highway will remain in this configuration except for regular closures Monday through Thursday from 10 a.m. to 2 p.m. as construction crews blast. Until Friday, the highway will remain closed, with an open window tomorrow from 8 a.m. to 3 p.m.

“We know how important it is to have the highway open for this weekend’s traffic,” said Caleb Lakey, ITD District 3 Engineer. “The response to the March 15 rock slide has been excellent, with many experts converging to address the problem quickly. I appreciate the public’s patience during this reduction in highway service.”

Sunday’s blasting work successfully mitigated travel risk in the area of the rockslide on ID-55 and experts feel confident that the hillside is now stable for safe, long-term travel through the corridor. Crews will finish removing the blast debris and cleaning up the area on Thursday.

From April 2 through mid-May, the road will be closed Monday through Thursday from 10 a.m. to 2 p.m., and open to one lane of alternating traffic with a 15-minute delay outside of the closure hours. For more information about the ID-55 Smiths Ferry Project, please visit itdprojects.org/projects/id55smithsferry/

update #10: 2:00 p.m. 3/29/2021

Over the weekend, Idaho Transportation Department contractors successfully removed an undercut outcropping of rock that remained from a rockslide near Smiths Ferry on March 15, completing a critical safety intervention to allow a return to normal work.

Rock blasting

The outcropping presented a considerable safety hazard to the public using Idaho Highway 55 below. ITD brought in a nationally-recognized team of geotechnical engineers to assess the situation and develop a blasting plan to remove the remaining material. The blast occurred Sunday at 4 p.m. after the road was closed for the day.

“It was a picture-perfect blast,” said ITD Project Manager Alex Deduck. “We needed to remove roughly 1500 tons of material sitting 30-50 feet above the roadway. The narrow landing area made this incredibly difficult, but the team did a great job.”

The blast required several days of preparation. A survey crew scaled across the rock face to determine drilling locations. Then, a blasting plan was drawn up. On Saturday, an excavator and drilling machine were flown above the rock face to drill holes and set charges.

“The use of a helicopter was cheaper and faster for us,” said Deduck. “The terrain here is steep and covered in trees. It would have taken several days to pioneer a path to the slide location.”

The blast area is now under a 48-hour observation period to watch for additional movement. Following that, the blasted material will be removed. The road will remain closed except from 8 a.m. to 3 p.m. every day, when a single lane of alternating traffic will be allowed. ITD encourages motorists to us U.S. 95 as an alternate route.

ITD will provide another update this Wednesday evening.

update #9: 8:30 a.m. 3/26/2021

Idaho Highway 55 continues to be open daily to one lane of alternating traffic between 8 a.m. and 3 p.m. Travelers can expect a 15-minute delay during this time and road closures outside of these hours.

The current traffic restrictions are expected to last through early April as crews work to remove the remaining rock outcropping. Drivers are encouraged to plan ahead, visit Idaho 511, and pay close attention to the message boards on ID-55.

Update #8: 2:00 p.m. 3/23/2021

Geotechnical crew scaling the rockface
Geo-technical crew scaling the rock face Monday

Starting Wednesday, March 24, Idaho Highway 55 will have daily openings to one lane of alternating traffic from 8 a.m. to 3 p.m. The road will be closed outside these hours. Travelers can expect at least 15 minute delays during this time. Crews will be actively monitoring the rock outcropping and are prepared to close the road immediately if weather or hillside conditions change. ITD recommends travelers, especially large vehicles, RVs, and trucks pulling trailers, still use U.S. 95 as the alternate route.

“We want to thank the public for their patience as we respond to this rock slide,” said Caleb Lakey, ITD District Engineer. “Our ITD personnel and contractor crews have worked nights and weekends to open the road and protect the public. While this is a major milestone, we recognize that there is still significant effort required to resolve this issue.”

ITD is working alongside national slide experts and finalizing plans to safely remove the remaining rock outcropping, which will require additional full road closures. These closures will likely begin in the next seven days. More information about the closures will be provided as it is available. Drivers are encouraged to plan ahead, visit Idaho 511, and pay close attention to the message boards on ID-55.

Update #7: 5:30 p.m. 3/21/2021

landslide next to highway with survey crew
A crew surveys the slide area on ID-55

ITD has been monitoring the rock slide throughout the weekend and determined that conditions continue to be unsafe in the area, and Idaho Highway 55 will remain closed to traffic.

“At this point, our ITD team can’t confidently open the road with the existing risks to the traveling public and crews,” said Caleb Lakey, ITD District Engineer. “Recent weather conditions paired with the weakened hillside, rock and soil from the slide has created a situation that requires further considerations before we can allow cars through. We know ID-55 is an important travel corridor in Idaho and we are working hard to open the road safely.”

Drivers are advised to use U.S. 95 as an alternate route. The next update will be provided in the afternoon on Tuesday, March 23.

Update #6: 1:50 p.m. 3/18/2021

A national rock slide expert has evaluated the slide that took place March 15 on Idaho Highway 55 and determined that the road should remain closed at least through Sunday, March 21 for safety reasons. ITD is working diligently to safely open the road to traffic and will monitor conditions through the weekend during the forecasted storms.  Working with experts, ITD will review conditions in advance of next week and provide another update during the afternoon on Sunday, March 21, so travelers can make appropriate travel plans.

“Safety of the traveling public, as well as the crews who are on site, is our top priority,” said Jason Brinkman, ITD District 3 Engineering Manager. “These decisions are not taken lightly. We understand that this road closure is not ideal, and are working extensively to reopen the road as soon as safely feasible.”

ITD continues to advise motorists to use U.S. 95 as an alternate route.

Panoramic photo of the slide, March 17th, 2021

update #5: 1:00 p.m. 3/17/2021

Idaho Highway 55 will remain closed today, through tomorrow. The Department continues to advise motorists to use U.S. 95 as an alternate route.

ITD crews monitoring the slide have seen continued movement of the hillside. The Department has called in nationwide experts to better assess the situation. These experts have assisted ITD in the past with the 2020 slide on U.S. 95 near Riggins. They will be on site tomorrow where we will asses how to proceed.

ITD will provide another update midday Thursday, March 18th.

update #4: 10:00 p.m. 3/16/2021

ID-55 near Smiths Ferry will remain closed due to the condition of the adjacent hillside. Safety is the top priority as crews continue to investigate the situation and work to reopen the road. Drivers shoulduse U.S. 95 as an alternate route. A status update will be provided midday Wednesday, March 17.

Update #3: 12:45 p.m. 3/16/2021

Crews are removing debris from the rockslide and working to open a single lane for travel. At this time, the closure will be extended beyond 2:00 p.m. today. Conditions are variable and no estimate can be given if the highway will open today or tomorrow. Motorists are encouraged to consider an alternate route.

Geotechnical engineers have conducted a preliminary assessment and believe there is risk more rocks may slide. Current work is focused on creating protection for at least a single travel lane on the highway from additional rockfall.

ITD has coordinated with emergency service providers to ensure critical services remain available for the community.

UPDATE #2: 11:25 A.m. 3/16/2021

Photo Gallery of slide added

update #1: 10:40 A.m. 3/16/2021

Idaho Highway 55 will remain closed while crews address the rockslide. The current plan is to follow closure protocols established for the highway project during a blasting event, which requires a complete closure from 10 a.m. to 2 p.m.

The slide removed rock and earth from beneath a spire on the hillside. The stability of that spire is uncertain and the area is considered dangerous. Motorists planning to travel between Valley County and Boise County should consider alternate routes.

Another update will be provided this afternoon.

Original post: 9:30 a.m. 3/16/2021

Late in the night on March 15th, a rockslide hit Idaho Highway 55 near Smiths Ferry, closing the highway. This is located within the work zone for the Smiths Ferry to Rainbow Bridge highway improvement project. However, at this time, there is no indication the work there directly triggered the slide.

There are no known injuries at this time. An excavator being used for the project did get hit.

Geotechnical experts are evaluating the situation. Given early observations at first light, the situation remains dangerous and the highway will remain closed.

“The rock and earth in this area is historically unstable,” said project manager Alex Deduck. “We saw a significant slide in 2019 just south of here. Last night’s slide is another example why our project is so important.”

The Smiths Ferry to Rainbow Bridge project will remove thousands of tons of rock and earth from the adjacent hillside to widen the highway, create rock catchment ditches, and reduce the severity of curves. Information about the project, as well as resources to sign up for email and text alerts, can be found at itdprojects.org/id55smithsferry/.

More information will be posted on this blog post as the situation develops.