Tenova Advanced Technologies (TAT) employs the Sensoil Vadose Zone Monitoring System (VMS) for heap leach and tailings dam applications.
The VMS technology enhances the monitoring of heap leach pads and tailings dams, and provides on-line temperature, moisture, pressure measurement and continuous solution sampling.
The VMS technology was originally developed for monitoring solution conditions in the Vadose (unsaturated) Zone between the surface and the water table for farming applications, chemical spills, tailing dams, tank farms, surface containment monitoring and has been also adapted for monitoring ore-heaps under leach.
The core of the VMS technology is a series of special probes with multiple discrete sensors and sampling devices encased in hard wearing flexible pipes which are distributed diagonally through the zone of interest. The monitoring units are composed of Flexible Time-Domain Reflectometry (FTDR) probes, which are designed to provide on-line measurements of water content, temperature and porous Vadose Zone Sampling Points (VSP). Solution samples collected continuously by the VSP in the subsurface are frequently analyzed in order to determine their chemical composition.
VMS System for Heap Leaching Applications
Heap leaching is a common extraction technique employed in the processing of metals such as gold, copper, silver and uranium. A typical heap leach operation involves ore excavation from open pit or underground mining, milling of the ore to a particular required size and then heaping the crushed ore on an impervious pad. The ore heap is subsequently leached with a solvent such as a diluted acid or a cyanide solution using an irrigation system such as sprinklers or drippers. Upon percolation of the leaching solvent through the heap, metal oxides dissolve from the crushed ore and drain to the bottom of the heap. As a result, this drained solution is now enriched (pregnant) with the desired metal and this is then processed to arrive at final product.
Real time monitoring of the heap’s hydraulic and chemical properties can therefore lead to significant savings in important and often scarce resources such as water (especially relevant in arid regions) and chemical inputs, as well as increasing overall mineral extraction efficiency.
More than 70 monitoring devices with a depth of more than 60 meters have been successfully implemented in various hydrological applications, including dams. The systems have been installed in Spain, USA, Israel, South Africa and Namibia.
VMS System for Tailings Dam Applications
The VMS system facilitates direct measurement of water flow and contaminant transport in unsaturated sediments, including earthen or embankments dams and dikes. The system enables operators, managers and safety authorities to receive “continuous real time” data on water percolation processes across the earthen dam or dike.
Having such real time data available can have profound positive implications on safety and potential damage warnings, including consequential damages and loss of life.