On Thursday, August 8th, 2019, a severe weather event in Little Cottonwood Canyon triggered several mud, rock, and debris slides which crossed SR210. The two largest slides were in the Tanners Flat/Maybird area and the Lisa Falls area. The initial manpower and equipment response included: Unified Police (UPD) and Fire Departments (UFA), Utah Department of Transportation (UDOT), Alta Marshal’s Office, Alta Ski Lifts Company, and Snowbird Ski and Summer Resort. The initial response focused on closing the road and maintaining traffic control points, hasty search of the roadway, evacuation of affected public, determining stability of roadway infrastructure, assessment of continuing hazards, and debris removal to establish emergency access between the upper and lower canyon.
Thirty five (35) vehicles and their occupants were discovered stranded between these slides. The majority of vehicle occupants were evacuated up canyon and were able to obtain shelter at Snowbird. A few people self- dispatched and were located walking out of the debris in the lower canyon. No serious injuries were reported or discovered during these operations. No missing persons were reported. Heavy equipment from Alta was able to breach the upper slide shorty afterward, allowing a passageway to the lower slide area. A helicopter from the Utah Department of Public Safety responded and worked with ground crews to verify that no vehicles had been buried in the debris and assisted UDOT in assessing the scope of the incident and damage to the roadway. UDOT was eventually able to breach the lower slide giving ground teams a better ability to verify that no-one appeared to be trapped in the debris.
EMERGENCY MANAGEMENT CENTERS:
No entity reported the inability to continue critical services and no declarations of emergency were made. Emergency Operations Centers (EOC’s) in the Town of Alta and Salt Lake County maintained an enhanced monitoring status. State of Utah Emergency Management Personnel responded to the canyon.
UTILITIES AND INFRASTRUCTURE:
- A large, undermined section of roadway below Tanners Flat revealed a large natural gas supply line that had been damaged and was in need of repair or replacement.
- Salt Lake City Public Utilities reported that water from Big and Little Cottonwood Canyon could not be used for culinary purposes, and began drawing their primary water supply from Deer Creek.
- Several shoulder locations along the highway were washed away from the edge of the roadway.
- Debris flowed into Little Cottonwood Creek but did not appear to alter the course of the waterway.
- Reports of damage to the Temple Quarry trail and parking area were received.
- Large runout areas/drainages above the highway were created by debris flow in several locations. Water continues to run onto the road in a few areas.
- Extent of damage continues to be assessed.
- Damage within the Town of Alta was modest, aside from degradation of the road to Grizzly Gulch.
Little Cottonwood Canyon was immediately closed and remained closed Thursday night with a single lane established for emergency vehicle access. Periodic, scheduled, supervised vehicle escorts of evacuees, canyon employees, and relief crews began Friday morning and continued until noon on Saturday at which time, sufficient roadway repairs had been made allowing two-way traffic. The highway was re-opened to the public at that time.
Debris removal and periodic traffic delays during daytime hours continue. Repair to the natural gas line is still underway. UDOT reports that repair operations will continue into the foreseeable future.