On a crisp, late fall day last year, less than 200 feet made all the difference on Idaho Highway 55.

Just after 2 p.m. on November 18, 2021, a traffic safety vehicle guided a line of cars through the tight construction zone in the canyon alongside the picturesque Payette River. A rumbling sound rocked the air. High above the road, tons of material crashed down from the blasted cliff face and spilled across the highway.
The slide came a mere 150 feet from crushing the Traffic-Corp pilot car and any others following behind on their way through the Central Idaho artery. It took weeks for the road to reopen to traffic.

This was the second of three major landslides that closed the corridor over the course of less than a year from March of 2021 through January, disrupting traffic between the Boise area and Valley County for days at a time. The slides all occurred within the construction zone for ITD’s ambitious multi-year project to flatten the curves of the winding, crash-prone highway snaking through the canyon.

• Six-month investigation
• Early rumblings of instability 
• First slide rocks the project
• Second slide strikes in spot with years of concerns 
• Major slide hits Cut 8 
• Cost overruns 
• Third time’s (not) the charm 
• ‘I will deny everything’ 
• Why did ITD build in the canyon in the first place?
• Timeline of events