ITD issues reminder on plow safety following six incidents in two weeks

Stock photo of another vehicle hitting a plow

Stock photo shown above. 

With snow in the forecast for several regions in the state, the Idaho Transportation Department would like to remind drivers how to travel with plows on the road.

In just the last two weeks, there have been four incidents of drivers striking plows and two incidents of drivers forcing them off the road. This compares to eight plow strikes recorded last year. Most of the collisions have occurred after other drivers tried passing plows on the right.

Drivers should be aware that most ITD trucks have two plows: one on the front, and one that extends from the right side known as a wing plow. Lights alert drivers to the presence of wing plows, but during storms those lights and the wing plows can be obscured by plumes of snow.

So far this winter, plows have been struck in nearly every region of the state:

  • On Dec. 9, a plow was hit on Interstate 90 near the Rose Lake exit when a driver tried to pass on the right.
  • On Dec. 14, a plow on U.S. Highway 95 near Moscow was forced off the road to avoid hitting a vehicle that had lost control and was in the opposing lane.*
  • On Dec. 16, a plow was hit on U.S. Highway 20 near Ashton and on Interstate 84 near Twin Falls. Both incidents involved drivers trying to pass on the right. That same night a plow on US-95 near Winchester was forced off the road to avoid hitting a vehicle that had lost control and was in the opposing lane.

The latest plow strike occurred this morning on I-90 near Osburn. Another vehicle attempted to pass the plow on the right, collided with the wing and forced the plow off the road. The driver then fled the scene. The Idaho State Police are investigating the incident.

To date no one has been injured. However, plows must be checked for any damage before being put back into service, which stretches resources thin with a direct impact to driving conditions.

“This time of year drivers need to take their time and never pass a plow on the right,” said Jerry Wilson, the operations engineer for North Idaho. “Let’s all get home safely.”

Know before you go and check 511.idaho.gov for road conditions before traveling. For winter driving tips, visit itd.idaho.gov/travel.

*Post updated Dec. 23 to reflect that this near-collision occurred on Dec. 17 on Palouse River Drive near the Moscow shed.

Idaho State Highway 55 reopens near Smiths Ferry

Update #9: 12:30 p.m. 12/6/2021

This is a view of the south end of the roadway and rock wall ready and safe for traffic prior to reopening SH-55 north of Smiths Ferry. The picture was taken on Sunday afternoon, December 5. If you look at the other photographs below in this blog and compare to this photo, you can get an idea of the tremendous amount of work crews did to stabilize the hillside.
This photograph was taken on Sunday afternoon, December 5 prior to the reopening of SH-55 north of Smiths Ferry. The picture is a view of the north side of the of the large rock wall buttress crews built to stabilize the slide.

Update #8: 4:35 p.m. 12/5/2021

SMITHS FERRY – Idaho State Highway 55 north of Smiths Ferry will reopen at noon on Monday, December 6. Travelers should be prepared for around 15 minute delays for the rest of the week, while crews continue additional construction activities to prepare the work zone for winter.

Stabilization work has been completed to fortify the hillside after more than 50,000 cubic yards of large boulders and dirt slid onto the roadway on November 18th. Construction crews built a 20-foot tall and 400-foot long rock wall to stabilize the area and are ready to open an interim road around the slide. Geotechnical experts have inspected the slide area and the contractor has completed the repairs to open for winter.

“The Department thanks the traveling public, Valley County residents, and the business community for their support and patience, as our crews worked tirelessly to stabilize this slide,” said ITD Engineering Manager, Jason Brinkman. “We know it’s been a long closure, but we have taken extensive steps to ensure safe travel through the work zone this winter.”

US-95 remains a viable alternate route for travel between Valley County and the Treasure Valley. The public can receive direct project updates by signing up for text or email alerts on the project website, itdprojects.org/id55smithsferry, or visit Idaho 511 before leaving on a trip to learn the latest highway conditions.

 

Update #7: 3:30 p.m. 11/28/2021

Idaho State Highway 55 between Smiths Ferry and Round Valley Road will remain closed another seven to 10 days depending on weather. Construction crews made significant progress today (Sunday, November 28) shoring up the rockslide area near the Rainbow Bridge about 20 miles south of Cascade, Idaho.

 

The crews completed construction of a rock structure, known as a buttress, approximately 20 feet tall and 400 feet long to stabilize the base of the slide. The next step is to remove slide debris, install drainage systems above the buttress and widen the roadway to two lanes before the winter.

 

“We have made very good progress and stabilized the slide area. This allows crews to remove excess rock from the hillside and begin building a two way road around the slide area,” said Jason Brinkman, ITD District 3 Engineering Manager. “Our goal is to finish the work as quickly as possible while also focusing on both the safety of the construction team and the public once the road reopens.”

 

Until the highway is reopened, travelers can use U.S. Highway 95 as an alternate route. 

Crews finished the rock structure, known as a buttress, at the base of the slide on Sunday, November 28, as seen in this picture.

The public can receive direct project updates by signing up for text or email alerts on the project website, itdprojects.org/id55smithsferry, or visit Idaho 511 before leaving on a trip to learn the latest highway conditions. 

UPDATE #6: 1:30 P.M. 11/24/2021

Crews are making progress on the rock wall to secure the rockslide on SH-55 near Smiths Ferry. The road is still anticipated to be closed through at least Nov. 29. Please note that US-95 is the alternative route for this closure. For safety, local roads are restricted to non-local drivers.

ITD appreciates your patience and understanding during this holiday weekend as crews work to restore service of the highway. If you do travel for Thanksgiving, remember to check 511 for the latest road conditions, give yourself plenty of time to reach your destination, and drive well

UPDATE #5: 1:30 P.M. 11/23/2021

Despite winter weather rolling through Idaho, work continues to secure the rockslide on State Highway 55 near Smiths Ferry. The road will remain closed through Thanksgiving weekend, at least November 29. Please plan ahead to use US-95 as the alternate route for your holiday travels. Check 511.idaho.gov for current road conditions.

UPDATE #4: 1:30 P.M. 11/22/2021

State Highway 55 between Smiths Ferry and Round Valley will remain closed through Thanksgiving weekend (at least November 29) as crews work diligently to secure the rockslide area near the Rainbow Bridge, about 20 miles south of Cascade.

Crews began work Sunday on an interim solution to safely open the road for the winter. The plan includes removing boulders and mud from the hillside to construct a rock wall approximately 20 feet tall and 500 feet long. Once the wall is built to reinforce the slope, a temporary road will be constructed around the slide to safely allow traffic.

“We appreciate the patience of the public as we work to reinforce the very large slide area,” said Jason Brinkman, ITD District 3 Engineering Manager. “Our goal is to reopen the highway as soon as possible. This is potentially dangerous work on an unstable slope. We need to take the time to ensure the safety of our construction team and eventually the traveling public once the road is reopened.”

Until the highway is reopened, travelers can use U.S. Highway 95 as an alternate route. A long-term plan for the rockslide area will be determined over the coming months. The immediate focus is to secure the slope before winter.

The slide is estimated to have brought down 30,000-50,000 cubic yards of material and debris. It measures nearly 200 feet from the top of the slide to the roadway and is approximately 250 feet wide along the bottom.

View of the work on 11/21/2021

The public can receive direct project updates by signing up for text or email alerts on the project website, itdprojects.org/id55smithsferry, or visit Idaho 511 before leaving on a trip to learn the latest highway conditions.

update #3: 4:00 p.m. 11/19/2021

ID-55 between Smiths Ferry and Round Valley Road will remain closed through the Thanksgiving weekend following a large rockslide that occurred on Thursday (Nov. 18) afternoon.

Geotechnical experts are onsite evaluating the safety and stability of the slope, along with determining how much material needs to be removed. The Idaho Transportation Department (ITD) recommends holiday travelers make plans to use U.S. 95 as an alternate route. The rockslide occurred during a scheduled road closure and no one was injured.

Construction crews are expected to begin clearing the road later this weekend. Crews will remove the large amount of material as quickly and safely as possible, weather permitting. ITD will provide regular updates of progress in clearing the road and evaluating the safety of the slope prior to the road reopening.

For regular updates drivers can check Idaho 511 or the project website at itdprojects.org/id55smithsferry.

UPDATE #2: 10:30 A.M. 11/19/2021

ID-55 near Smiths Ferry remains closed in both directions while experts assess the slide. ITD is working diligently to safely open the road to traffic and will provide an update late this afternoon, Nov. 19, so travelers can make appropriate plans.

“We understand the inconvenience closing down the road causes, but our objective is to ensure the corridor is safe for travel,” said Jason Brinkman, ITD District 3 Engineering Manager. “These decisions are not taken lightly. We appreciate the public’s continued patience as we work to clear the debris and reopen the road safely.”

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

UPDATE #1: 3:50 P.M. 11/18/2021

ID-55 will be closed in both directions at least until tomorrow, Friday, Nov. 19, while crews assess the slide. Use U.S. 95 as alternate route.

ORIGINAL POST: 2:45 P.M. 11/18/2021

ID-55 will be closed in both directions until further notice, due to a rockslide. Please use U.S. 95 as alternate route. Updates will be posted on this blog as well as on the project website. You can also sign up for email and text alerts.

PHONE: (833)913-ID55
EMAIL: info@ID55smithsferry.com
ONLINE: itdprojects.org/id55smithsferry

It’s time to be “Idaho Ready” for winter driving

Ahead of the busy holiday travel season, the Idaho Transportation Department (ITD) encourages drivers to be “Idaho Ready” for winter driving. ITD’s annual winter safety campaign aims to help drivers prepare for challenging conditions on the state’s highways, before hitting the road.

“Idaho Ready” tips and resources will be shared weekly through ITD’s social media accounts and website itd.idaho.gov/travel. Short videos, blog posts, infographics, and photos will teach drivers how to safely get around this winter. Planned topics include navigating the new Idaho 511, general winter driving tips for Idaho newcomers, how to keep vehicles ready for colder temperatures, and snowplow ride along videos to hear safety advice straight from ITD operators.

Each winter ITD’s 550 hardworking snowplow operators travel a combined 3.4 million miles clearing roads across the state. “Idaho Ready” also focuses on keeping these important employees safe. When encountering a snowplow on the road, drivers are reminded, the safest place is behind the plow—never pass a snowplow on the right.

Other quick winter travel tips:

  • Check the road conditions before traveling. Visit 511.idaho.gov or download the Idaho 511 app for an easy look at weather reports, cameras, and more. Idaho 511 updates are now tweeted too! Follow @Idaho511 on Twitter.
  • Keep a winter emergency kit in your car with food/water, small shovel, warm blanket, etc.
  • When roads are wet or icy, slow down and give yourself more stopping distance. Turn off cruise control and remember, bridges and overpasses are the first to freeze when temperatures drop.
  • If you do slide, stay calm, brake very gently, and turn your wheel in the direction of the skid. Try not to overcorrect.
  • Keep your windshield completely clear of snow and ice. Fill up on windshield washer fluid, make sure your tires are in good shape, and battery is charged. Learn how to use tire chains and carry them with you.
  • Give our snowplow drivers room to work. Never pass a snowplow on the right! The safest place is behind the plow where the road is clear.
  • Let others know your travel plans, especially if you will be driving through areas with no cell service. Check in when you make it.
  • Beware of drowsy driving! Stop and rest when needed, and plan breaks on long road trips. Rest areas are mapped on Idaho 511.
  • If your holiday celebrations include alcohol, plan ahead for a sober ride home. Look out for your friends and family and help them get home safely too.
  • Buckle up, stay engaged behind the wheel, and drive for the conditions this winter.

Follow along with ITD and the Idaho Ready campaign this winter:

ITD wins trio of national transportation awards signifying industry excellence

The Idaho Transportation Department won three national awards in the AASHTO President’s Transportation Awards, announced Friday (Oct. 29) at the group’s annual meeting in San Diego. The American Association of State Highway and Transportation Officials (AASHTO) is the national organization overseeing all the departments of transportation from each state in the country.

“Over the past 12 years, the culture has shifted at ITD to a workplace where employees are encouraged to innovate, collaborate, and make decisions as close as possible to where the work is being done,” said ITD Director Brian Ness. “Our team has embraced this philosophy. The end results are award-winning projects that improve customer service for the citizens of Idaho.”

Under Ness, ITD has won 20 AASHTO Presidents Awards, more than any other state in the nation.

ITD won awards in the following three categories this year:

  1. Environment, for Building Wildlife Sanctuaries as part of bridge projects in south-central Idaho
  2. Highways, for Pennsylvania Ave. Overpass project in Coeur d’Alene
  3. Highway Traffic Safety, for I-84 Traffic Corridor Safety and Commerce Enhancement project

Environment award

A pair of bridges constructed on US-20 in south-central Idaho replaced culverts over Willow and Rock Creek, remedied the failing multi-plate metal culverts that prohibited fish spawning and wildlife migration for decades, and restored wildlife habitats and streams for safe fish passage under the highway.  The project also addressed vehicle-wildlife collisions by building animal crossings into the design of the bridges. The Rock Creek bridge section of US-20 saw 64 vehicle-wildlife collisions over the last five years alone. Idaho Fish & Game and ITD installed game cameras to monitor the environmental benefits of the projects, and within a few months, fish were discovered swimming upstream to spawn, and multiple deer (and a moose) were seen traveling along the channels under the bridges.

Highways award (pictured at top of page)

ITD replaced two concrete bridges carrying Interstate 90 traffic over Pennsylvania Avenue in Coeur d’Alene with one bridge. To limit the duration of impacts to the traveling public, the project used Accelerated Bridge Construction (ABC) methods, which simplified construction and reduced the amount of on-site concrete formwork required. The bridge abutments, piers, and girders were cast off-site in nearby Spokane while work proceeded at the site. Several key changes allowed the bridge to be constructed faster and more effectively. For instance, a high-early strength concrete cut more than 60 days of cure time from the overall project. The bridge provides a great improvement for the community and drivers on the primary route through the largest metropolitan area and tourist destination in north Idaho. Additionally, the new bridge design allows up to six traffic lanes on I-90 in the future, if needed.

Highway Traffic Safety award

ITD won this award for the work on Interstate 84 through the Treasure Valley, the most heavily traveled route in the state, which sees more than 130,000 vehicles per day. The work kept travel lanes open and moving, was delivered under budget and on time and utilized a new-to-Idaho method to enhance safety in the construction corridor. That safety provision was a towing service that moved disabled vehicles off the road and out of the travel lanes to keep traffic moving and assist first responders. Law enforcement was averaging 1.5 hours per incident prior to the implementation of the Safety Service Patrol.  The service also saved hundreds of hours for the traveling public and millions of dollars for shippers.

US-26 in Idaho officially named POW-MIA Memorial Highway during ceremony and sign unveiling in Carey

Image of US-26 POW-MIA Memorial Highway Sign Locations

Idaho legislators, representatives from the National League of POW-MIA Families, community members and the Idaho Transportation Department will officially celebrate the naming of US-26 in Idaho as the “POW-MIA Memorial Highway” at 2 p.m. Wednesday, October 6, 2021, at the Carey City Park – Boyd Stocking Pavilion.

During the 2021 Idaho legislative session, HB132aa sponsored by Representative Scott Syme and Senator Patti Anne Lodge, formally designated and named US-26 in Idaho, the POW-MIA Memorial Highway. The bill unanimously passed both chambers, respectively, and was signed by Governor Little in April.

Idaho is home to eight soldiers designated as MIA and the City of Carey happens to be home to one of those individuals. Jon Michael Sparks was a helicopter pilot for the US Army and was lost in Long Binh Province, Laos, on March 19, 1971.

US-26 in Idaho runs from the Oregon border to the Wyoming border. The highway naming is part of a nationwide effort to designate US-26 as the POW-MIA Memorial Highway from coast to coast, with several other states participating over the years as well.

There are 10 locations across US-26 in southern Idaho where new POW-MIA Memorial Highway signs will be installed.

ITD seeks feedback on draft Americans with Disabilities Act Transition Plan update

As the Idaho Transportation Department updates its Americans with Disabilities Act (ADA) Transition Plan, the public is encouraged to learn more about plans to invest nearly $35 million into projects and services over the next 15 years.

ADA Transition is the process of eliminating accessibility barriers to existing pedestrian infrastructure on the state highway system. It also helps identify programs that fund improvements through a coordinated effort with local highway districts and other municipalities.

In an effort to gather feedback about the plan, ITD will host an online survey as part of a 30-day public comment period that begins Sept. 17. The survey can be accessed at itd.idaho.gov/planning by clicking on the link. The survey is available 24 hours a day.

Staff will also hold a virtual public information meeting on Tuesday, Sept. 28 at 6:00 p.m. Mountain time. 
You can find the meeting link posted online at itd.idaho.gov/planning or by emailing ADA@itd.idaho.gov.

Comments and feedback shared during this public involvement phase will be incorporated into a draft ADA Transition Plan, that will become official after review and approval by the Federal Highway Administration and Idaho Transportation Board later this fall.

For questions or to learn more about ADA Transition, please email ADA@itd.idaho.gov or call (208)332-7823.

Middleton City Council considers removal of future highway alternate route

Four lane highway

On Wednesday, September 15, the Middleton City Council will consider a revision to its Comprehensive Plan regarding the future Highway 44 that will have ripple effects for transportation far beyond the city limits.

For the last two decades ITD has partnered with City of Middleton leaders to develop an alternate route for the highway that would be constructed to the south of the current roadway. The City Council will consider eliminating the alternate route from its comprehensive plan and approve new development that would build on top of the open space currently slated for the future highway.

The future alternate route was shared at two public meetings in 2019. You can see the click on the links to see the West Half and East Half of the proposed route.

What happens to the future of the highway?

Graphic: Existing traffic, ten thousand trips per day. 2045 no-build traffic, twenty-four thousand trips per day.

The last two decades of work have laid the groundwork for a transportation network that can support the extreme growth in Middleton, Star, and Eagle.

The growth projections for the Middleton area, which are somewhat conservative, suggest 24,000 cars will drive on the highway by the year 2045. Today, the daily trip count is around 10,000. Congestion already experienced will only get worse. As highway congestion increases, typically the number of crashes also increases.

ITD’s Mission is “Your Safety. Your Mobility. Your Economic Opportunity.” These three pillars of the Department go hand-in-hand. Fewer crashes keeps people moving, energizing commerce. The alternate route for Highway 44 would achieve these goals while accommodating for the forecasted growth in the area.

Take away the option of a future alternate route, and what happens to highway traffic is uncertain. ITD has looked at a couple options at a high level. The first option is to keep the highway as-is.

Graphic: significant delay on highway 44 in 2045 no-build scenario

The biggest “pro” of that option is the existing buildings downtown will not be impacted. The biggest con is pretty obvious – there’s no way the existing three-lane highway will effectively move 24,000 cars a day. ITD’s projected level of service for downtown intersections has nearly all of them seeing excessive delay times. In some circumstances, it could take you more than five minutes to get onto the highway from a local road.

The second option would be to add capacity to the existing highway to move more vehicles. This option is not without its downsides. We’ll share three big ones.

Impacts to existing businesses and land use

The first is the available space for the lanes. Near the fire station in particular, there is not enough room to add more lanes. In order to fit everything in, ITD will likely need to purchase existing buildings and demolish them. A preliminary scan of the total impacts of a widened highway suggests 76 different properties will be negatively impacted.

Graphic: property impacts of 100' for highway expansion
Possible property impacts to accommodate 100 feet for additional highway lanes.

Impacts to access

The second pain point comes with the existing number of roads and driveways accessing highway 44. Every access point introduces conflicts between vehicles, pedestrians, and cyclists using the roadway. Transportation engineering reduces these conflict by removing accesses or restricting the movements in and out of those access points.

In order to promote safety and mobility on the existing highway alignment, ITD will likely need to install median curbs, restricting left turns on and off the highway. Similar action was taken on Eagle Road. The diagram below provides a sense of what that means for local travel options.

Graphic: access restrictions to most local roads in downtown Middleton
Similar to Eagle Road, future access on ID-44 could be restricted to right-in, right-out.

Delay for improvements

A third downside is the delay this will force on any improvements to the highway in Middleton. The process to achieve environmental clearance has taken nearly two decades already. Should the alternate route be removed from Middleton’s Comprehensive Plan, the clock on those efforts will be reset.

Environmental clearance is needed to get federal funding for transportation improvements. Pushing back that clearance another decade or two means the highway in Middleton won’t qualify for those dollars, ITD’s biggest bucket of money. Meanwhile, growth and congestion will continue.

The Council Decision

ITD has partnered with the City of Middleton on the future of Highway 44 for more than two decades. We will continue to do so. The Department strongly recommends the Council continues the City’s historic support for the alternate route and preserve the corridor in the Comprehensive Plan.

Regardless of the Council’s decision, we are committed to provide the best customer service we can. Our goal in sharing this information with the public is to bring clarity to a complicated process and to understand the downstream consequences of a decision. The folks at ITD are your friends, neighbors, and relatives. We want to see the community of Middleton grow and thrive. It is our belief that open dialogue and the best information will bring about the best results for us all.

ID-55 project between Smiths Ferry and Rainbow Bridge to resume road closures after Labor Day

Work on Idaho Highway 55 near Smiths Ferry will shift to a fall closure schedule starting Wednesday, September 8, after the Labor Day holiday weekend.

Travelers can expect ID-55 to be closed Monday – Thursday from 10 a.m. – 2 p.m. due to controlled rock blasting. Outside of these hours, one lane of the highway will be open to alternating one-way traffic. This schedule is anticipated to continue through mid-November, when crews will pause work and fully reopen the road for the winter.

Drivers should keep in mind, the full road closures can create a buildup of traffic in the afternoon, which flaggers need to fully clear from each end of the work zone. This can extend wait times immediately when the road reopens at 2:00 p.m. Crews ask for drivers’ patience and to plan accordingly when traveling to and from Valley County.

The project, scheduled to be completed by fall 2022, will soon begin the process of building retaining wall on the riverside, pinning back rock, and straightening the roadway. Watch a video from the work zone below.

 

“We have managed to accomplish a great deal of work on this project so far,” said Alex Deduck, ITD Project Manager. “To date we have excavated about 100,000 cubic yards of material which allows us to expand the shoulders by four feet in the canyon. Ultimately, this project will make passage in the canyon safer for drivers.”

ID-55 is one of the most heavily traveled highways in the state of Idaho. In 2020 alone, ITD recorded approximately 1.5 million vehicles driving on ID-55 and predicts 2021 will see similar, if not higher, numbers.

“Our goal with any project we take on is to ensure drivers are safe,” said Vince Trimboli, ITD Chief Communication Officer. “If we can reduce the risk for travelers on our roads, especially on these curvy mountain roads, then we have done our job well.”

To read more about the project and sign up for updates and alerts, visit the project website: itdprojects.org/ID55smithsferry

ITD to meet with freight stakeholders

A truck climbs a hill

The Idaho Transportation Department will meet with freight stakeholders across the state this September to collect feedback and update its freight plan.

The Idaho State Freight Plan identifies how ITD will strategically invest state and federal funding in infrastructure to increase the safety, capacity and efficiency of the freight system for the benefit of the Idaho economy.

The document analyzes the needs and issues in Idaho, details policies and strategies to overcome them, identifies critical freight corridors and lists projects to be funded. These projects are supported by approximately $10 million of federal funding each year.

Freight stakeholders utilize infrastructure on a daily basis for basic operations and produce, ship/receive or transport the majority of goods within the state. Such industries include: agriculture, forestry, fishing and hunting, mining, utilities, construction, manufacturing, wholesale trade, retail trade and transportation and warehousing. Those who would like to participate in the process should contact Scott Luekenga at (208) 334-8057 or scott.luekenga@itd.idaho.gov to get details on the available times and locations.

Participants will be guided through a 30-minute survey based on their industry. They are invited to engage in person at the following events:

  • Lewiston on Sept. 2
  • Blackfoot on Sept. 16
  • Twin Falls on Sept. 21

Virtual opportunities will also be accommodated through the end of September. Another round of public comment is expected in spring 2022 to review the updated plan.

New landslide database provides tool for project development and hazard mitigation

The Idaho Geological Survey (IGS) is helping the Idaho Transportation Department (ITD) learn more from landslides in the Gem State. A new statewide inventory database of landslide and rock fall hazards released by IGS in late June will assist ITD, emergency managers, and planners with forecasting and hazard mitigation by identifying problematic hot spots.

The project was sponsored by ITD’s Division of Highways – Construction and Materials team and funded through ITD’s Research Program.

The inventory contains more than 2,400 landslide entries spanning from prehistoric to active events. It’s posted on the IGS website and can be accessed through an interactive webmap service.

The information was also added to ITD’s IPLAN online ArcGIS platform. The database includes attributes to maintain MSE retaining wall locations and risk factors to evaluate the condition of the wall, as well as attributes for rock fall risk, so ITD districts can assess the problematic areas that could cause road closures.

Data were compiled from historic archives, information provided by ITD geotechnical staff and district geologists, unpublished IGS field observations, analysis of LiDAR imagery, remote sensing, satellite images, and newly mapped landslides.

“The study represents a live catalog of mass movements across the state with a particular focus on transportation corridors and urban areas,” said State Geologist and IGS Director Claudio Berti. “The database is a tool for documenting and assessing slope stability hazards. It is not intended to predict future events, but to document known events and show broad patterns of occurrence.”

This new database replaces the last inventory published in 1991, a static map no longer suitable for modern digital analyses. The 2021 version will be kept up to date as new events occur or new information becomes available.

Landslide problem areas in Idaho include: Bonners Ferry, Clearwater River Basin, Horseshoe Bend, Boise Foothills, Hagerman, U.S. 95 between Pollock and Lucile, and U.S. 26 between Swan Valley and the Wyoming border. Geologic characteristics of the bedrock, fractures, systems, precipitation, regional hydrogeology, vegetation, wildfires, and steepness of hillslopes are all contributing factors in landslide initiation and development.

You can also learn more by reading the full research report linked here.