The Landslide Blog is written by Dave Petley, who is widely recognized as a world leader in the study and management of landslides.
At about 5 a.m. local time on 11 May 2024, a significant tailings landslide occurred at a facility operated by Greenstone Resources Corporation (GRC) at Siana in Surigao del Norte, Philippines. Fortunately there are no reported fatalities, but a number of houses have been destroyed.
This event has been widely reported the Philippines, making it comparatively easy to track down. The image below is from Google Earth, collected in 2021, showing the large pit from which gold was extracted (on the right side), the tailings storage facilities (in the centre) and, to the south, the village of Siana, including the elementary school:-
The location of the tailings facilities is [9.542, 125.573]. There is some detailed information about the mine and the tailings facilities on the TVI website, including some photographs. The tailings facility that failed is reported to be TSF3.
There are a couple of videos showing the landslide in action, indicating that the rate of movement was mostly slow, but incessant. This one shows the progressive demolition of a house, for example:-
This one is rather longer, but captures the chaos of the evacuation, and also shows the landslide moving through the community (take a look at about minute 8 in the video):-
Some news reports provide what appears to be a detailed narrative about the sequence of events. It indicates that the operator, GRC, identified cracks in the tailings facility at Siana a few hours before the landslide, and organised an evacuation of the residents. MindNews reports that this was a tailings facility from an earlier phase of mining, operated by an Austrlian company, Red 5. The facility was apparently designed by a global engineering and environmental consultant and built by Suricon. GRC, who reopened mining at Siana having bought the facility in July 2021, claims not to use TSF3.
The weather at the time of the failure appears to have been good, with news reports indicating that the trigger might have been some combination of recent seismicity and/or recent heavy rainfall. This will need further investigation. Tailings landslides do not necessarily need an external trigger.
If nothing else, this landslide will serve to highlight an issue raised frequently by World Mine Tailings Failures, which is that abandoned tailings facilities pose a substantial risk that is often being under-appreciated.
GRC has paused all mining activity at Siana, and the failure is being investigated by the Department of Environment and Natural Resources (DENR) in the Philippines. According to PhilStar, this investigation will examine “the cause of the incident, its impact on surrounding communities and the environment, and the integrity of the mine’s tailings facility, safety systems and procedures”. It will be interesting to see what it finds.
Of interest will be a news report from 2014, when the mine was being operated by Red 5, which indicated that mining operations had been paused after “studies concluded that the mine’s tailings dam wall has been compromised”. Mining was allowed to restart on that basis that a series of actions were taken to improve tailings storage at Siana.