17 October 2017
The Bellavista heap leach gold mine landslide in 2007
On 21st October 2007 a landslide effectively closed the Bellavista heap leach gold mine in Costa Rica. This landslide is subject to a court case that is currently being heard in the Ontario Superior Court of Justice, with a claim if about $100 million being made against SRK Consulting (US), who undertook engineering and design work, by B2Gold, based in Vancouver.
Cyanide heap leaching involves creating piles of crushed ore, mined from an open pit site in this case, which are then washed with cyanide solution. The leachate is then collected at the foot of the pile, allowing the gold to be extracted. Clearly the risks of pollution are sufficiently high that great care is needed to protect the integrity of the heap. The Bellavista site is located in heavily weathered, humid tropical mountains that are also seismically active. Slope instability is a challenge in such environments, as multiple examples on this blog have shown.
The Tierra Group has a description of the work that they undertook at the site in 2007, which includes this image of the ore heap:
In their description of the project, the Tierra Group state that:
…our Team performed a geologic hazard assessment which ultimately identified existence of a mega-landslide (35,000,000 m3) underlying a waste rock dump and flanking a heap leach pad. A site wide Environmental Audit was prepared for the Secretaria Técnica Nacional Ambiental.
This landslide induced instability in the heap; unconfirmed reports suggest that movement was observed in 2006. The mine was reportedly closed in July 2007. In October 2007 a major landslide occurred in the southeast corner of the heap. The Ecologist has this image of the landslide, taken in January 2009:-
After this major landslide, the mine was closed and has subsequently been remediated. Of course I cannot comment on the liability issues that this case raises (and I cannot comment on the validity of any of the legal claims for obvious reasons), but once again problems of slope instability and mining are clear.