Key Takeaways
- All nine victims of the Feb. 17 Castle Peak avalanche died of asphyxia, not traumatic injuries, according to coroner reports released by Nevada County.
- The dead included three guides and six clients; several were Bay Area women on a backcountry ski trip.
- Burial depth was initially reported as 5 to 8 feet, but autopsy reports narrowed the range to 5 to 6 feet.
- Investigators say the group traveled together through avalanche terrain while the danger was rated high.
- The Nevada County Sheriff's Office is still conducting a criminal investigation and Cal/OSHA is also reviewing the incident.
Introduction
Partially redacted coroner reports released Thursday, Aug. 6, confirm that all nine skiers killed in the Castle Peak avalanche near Lake Tahoe died of asphyxiation. The findings solve one mystery but leave many others unresolved, including what happened in the group's final minutes and why basic safety measures were apparently skipped.
What the Autopsy Reports Show
The Nevada County Coroner's Office said all nine victims died from asphyxia after being buried by snow. According to the San Francisco Chronicle, the victims died within minutes after a 100-foot-wide wall of snow cascaded 400 feet down the mountain northwest of Truckee.
Asphyxiation is the leading cause of avalanche deaths. A study cited by the Tahoe Daily Tribune found it accounts for about 75% of fatalities. Burial depth is critical: victims buried deeper than 6.5 feet have only about a 10% survival rate, while those under 1.5 feet have an 80% survival rate.
Asphyxiation occurs when the body does not receive enough oxygen. During avalanches, it can happen in three ways: when the airway is obstructed by snow, when the chest cannot expand due to snow weight and compaction, or due to hypoxia resulting from rebreathing the same air in a confined space.
In this case, earlier reports from the Sierra Avalanche Center said the skiers were buried 5 to 8 feet deep. The autopsy reports narrowed that range to 5 to 6 feet, and noted that heavy snow continued falling after the slide.
Redacted Sections and Unanswered Questions
The reports are heavily redacted. Sections covering drug and alcohol use, injuries, and the condition of victims at the scene were blacked out. That means it is still unclear whether any victims also suffered injuries before being buried, and whether any had substances in their systems.
Not every avalanche victim dies from suffocation. People can be killed by the force of the snow or by being swept into trees and rocks. The redactions make it impossible to know if additional injuries played any part in the deaths.
What Led to the Slide
The group of 15, including four guides, left Frog Lake Huts on Feb. 17 during a blizzard to return home. The avalanche hit the group near Castle Peak, a summit visible from I-80 across from Boreal ski resort.
Accounts differ on how many escaped the initial slide. One earlier report says the avalanche hit all but three members, while the San Francisco Chronicle says five others, one guide and four clients, avoided the snow and survived.
The Sierra Avalanche Center had rated the danger as high, one step below extreme, with large to very large slides considered likely. A later report by the U.S. Forest Service National Avalanche Center and the Colorado Avalanche Information Center found that the group traveled close together below avalanche terrain and through the runout zone of an avalanche path.
The report said exposing only one person at a time to avalanche terrain is accepted best practice, and that groups of four or more have a higher chance of being caught. A Sierra Avalanche Center expert also said the slide was likely triggered by the ski party itself.
Additionally, several members carried avalanche airbag backpacks, but none of the devices deployed, according to the San Francisco Chronicle.
Nevada County and the Sierra Backcountry
The avalanche occurred in Nevada County, near Truckee and Soda Springs. Six of the victims were close friends, many of them Bay Area residents who kept homes in Soda Springs. The three guides who died were from South Lake Tahoe, Verdi, Nevada, and Tampa, Florida.
The deaths have shaken the close-knit backcountry community around Lake Tahoe, where guided ski trips are a common way to access the Sierra Nevada in winter.
Background
The Feb. 17 slide is considered the deadliest avalanche in modern California history. The trip was operated by Blackbird Mountain Guides, a Truckee-based company. Shortly after the avalanche, the Nevada County Sheriff's Office opened a criminal investigation into possible liability, and Cal/OSHA began looking into worker-safety violations.
Conclusion
The coroner's finding answers how the nine victims died: they suffocated under the snow. Bigger questions remain about how experienced guides led a large group into high-risk terrain and whether anyone will face consequences. The sheriff's investigation and Cal/OSHA review are ongoing.