Geo Hazards

Subheading: Landslides, Subsidence, Sinkholes, Earthquakes, Floods, Seismic faults, Sea-level rise

Rattlesnake Hills Landslide

Case Background

In late 2017 ground disturbances were noticed above a quarry in the Rattlesnake Hills of Yakima County in central Washington, causing a slow-moving landslide. 

The landslide resulted in a precautionary but indefinite road closure, immediate evacuation due to imminent danger for a neighborhood of around 70 people south of the affected area, multiple crisis contingency plans including the slide's impact on the nearby Yakima River, and actively tasked resources of over 10 local, state, and federal agencies. The economic impact of the slide seemed to compound as reports indicated that in addition to the quarry and state both hiring independent consultants to further study the slide, the quarry parent company offered five weeks of paid hotel stays for displaced residents. 

Technical Background 

Quarry mining operations were halted once the vulnerabilities were identified and close monitoring of the area began, including installation of more than 50 GPS monitors, four seismometers, aerial imagery, and terrestrial LiDAR, among others. Efforts were also taken to physically block the landslide. 

In May 2018 the landslide, approximately eight hectares (20 acres) in size, was estimated to be moving at a rate of 45 centimeters (1.5 feet) per week, according to the Washington State Department of Natural Resources. The Seattle Times reported in June 2018 that the landslide was still being monitored though it had slowed movement indicating that it could be coming to an end. It was estimated that eventually, the landslide would contain itself after enough rocks and debris collect into the quarry below. 

SILLE Advantage 

Through displacement reconstruction, InSAR data shows the emerging safety risk of Rattlesnake Hills beginning in 2015 and steadily continuing into 2018. Satellite data shows dramatic negative displacement on the western-facing side of Rattlesnake Hills, consistent with the identified landslide. 

Had SILLE been implemented into the scope of monitoring this quarry, its weekly scans would have revealed the effects of the mine early enough to spur precautionary measures allowing time to minimize the landslide's risk to residents. 

The value of SILLE is clearly seen in its ability to establish subsidence history and systematically monitor any size area without in-situ equipment. The service complements existing analysis techniques to provide a comprehensive look at surface displacement and structural shifts. Within the application users are able to collect, analyze, store, and export data, allowing for multidimensional use. 

SILLE Risk & Resource Savings

• Improve understanding of timeline & reasons for the occurrence
• Implement preventative measures to avoid a crisis
• Analyze historical displacement for better prediction of future trends
• Minimize the costs of corrective efforts
• Maintain positive public opinion by circumventing potential disaster