SOLUTION MANAGEMENT

Once sufficient new ore has been stacked on the pad, the solution distribution piping is extended and the newly-stacked area placed under irrigation. Biooxidation is rapidly initiated as the new area is populated with active, adapted microbes introduced with the solution and recycled with the ILS. Solution is applied at variable rates of 2-20 L/h.m 2 by conventional irrigation equipment, and percolates through the heap to the drain layer where it is collected in perforated piping. The drainage pipes conduct the solution to a collection ditch running along one of the long sides of the heap. The ditch discharges into the appropriate pond based on grade and pH. Solution is pumped from the ILS pond back to the distribution piping and sprinklers on the active areas of the heap. The PLS solution reports to downstream metal recovery.

In cold climates and at high altitudes plastic sheeting may be applied to the surface of the heap to help conserve heat.

During periods of heavy rainfall, it may be necessary to reduce or eliminate the addition of fresh make-up water to the system and to maintain the PLS grade by reducing the solution bleed rate. In extreme cases, low-grade solution may be diverted to an emergency pond and later returned to the ILS pond as make-up. A detailed water balance, taking into account the site climatic conditions, must be performed for each GEOLEACH ™ project and the results used to size operating ponds and emergency storage ponds.