While most mining companies have shifted from a previously accepted sprinkler method to the percolation of slowly dripping choice chemicals (cyanide or sulfuric acid) closer to the actual ore bed (Krauth 1990), heap leach pads have not changed too much throughout the years. There are still four main categories of pads: conventional, dump leach, Valley Fills, and on/off pads.
Typically, each pad only has a single, geomembrane liner for each pad, with a minimum thickness of 1.5mm (usually it is thicker).
The simplest in design, conventional pads are used for mostly flat or gentle areas and hold thinner layers of crushed ore. Dump leach pads hold more ore and can usually handle a less flat terrain. Valley Fills are pads situated at valley bottoms or levels that can hold everything falling into it. On/off pads involve the use of putting significantly larger loads on the pads, and removing it and reloading it after every cycle.