Mining Methods Vary Widely - Mining and the Environment: From Ore to Metal - page 234

FIGURE 5.6
A Bird's Eye View on a Field of
Expanding Heap Pads

Photo credit:
www.airphotona.com

TABLE 5.2
Comparison of Leach Pad Approaches

Consideration Reusable Pad Expanding Pad Valley Leach Method

Land area required Small Large Moderate

Topography
required

Flat or gently sloping Flat or gently sloping Incised valley including steep terrain

Climatic factors Not suited to high rainfall situations 1 Requires dry climate Suitable for wet climates

Pond sizes Small Large Ponds not usually required

Liner requirements High impact resistance required

due to repeated exposure/traffi c

Relatively low stress environment
may allow lower resistance liner

High resistance due to high pressures

Ore variability Requires ore of consistent leachability Can be adapted to ores of varying

leachability

Can accommodate ores of varying leach-
ability including ores requiring extended
leach times

Rehabilitation Not possible until operations cease

(except for spent ore storage)

Segments can be rehabilitated
progressively

Outslope can be rehabilitated
progressively

Other Requires separate spent ore storage Low initial capital cost Requires retaining impoundment

1 Installation of roof or other cover above heap can overcome this limitation.

that are more transferable to other industries. Transferable skills learned by heap leach
personnel include pipe laying, irrigation systems, operating and maintenance of pumps
and controls, surveying, earthworks, liner construction and maintenance, slope and ero-
sion control, reclamation and revegetation, and various other aspects of civil construction.

3. Environment - Heap leach facilities in general have had far fewer serious ARD prob-

lems then conventional milling operations, in part because by leaching lower grade ore
they can reduce the size (and for a copper project, the sulphide content) of the waste