Slope stability issues in a tailings dam wall at Vale’s Brazilian Gongo Soco mine have triggered a range of preparedness measures in anticipation of another dam wall failure.
Vale reported that its Brazilian Gongo Soco mine, in Barão de Cocais (Minas Gerais), is under 24-hour remote monitoring, using slope stability radars and other robotic stations to detect millimetric movements of the dam structure. The company also confirmed that they are using drone technology to assist in the monitoring of the slope stability at the mine’s Gongo Soco tailings dam.
Vale confirmed that according to the current monitoring data from the slope stability radar installed at a nearby mine site, there is a possibility of ground failure the North Slope of the pit, which is located 1.5 km away from Sul Superior dam.
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Slope stability radars
are capable of detection of a range of millimetre ground deformations across a range of distances and have been used successfully in accurately detecting a ground failure in mining for several years with significant accuracy.
In a media release Vale said that there is ‘no technical information so far to state that the eventual slide of the north slope in the pit of the Gongo Soco mine will cause a breach of Sul Superior tailings dam’ however in view of the Brumadinho disaster it is reinforcing the level of alertness and readiness for the risk of a breach.
Vale said it is continuing to work with authorities to provide clarification of issues surrounding the slope stability potential issue and the potential effects on the dam. It also confirmed that engineering controls (in the forms of earthworks) for the construction of a concrete containment structure located 6 km downstream of the Sul Superior dam. The new structure has been designed to accept the full volume of tailings from the Sul Superior dam in the event of a major breach.
On Saturday the company conducted a trial evacuation of approximately 1,600 residents as a trigger response to the identified slope stability issue. The trigger response action was implemented by Brazilian Government agencies. Vale says that ‘350 Vale employees joined the activity and provided all logistical support to the relevant agencies.’
The Sul Superior dam has been at Level 3 safety warning since March 22. On February 8, Vale removed 400 residents from a zone in direct proximity to the dam. Vale says that they were accommodated in provisional houses rented by Vale, as well as in hotels and inns of the region, while others preferred to stay with their relatives.
Image: Google Earth.
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