RECLAMATION AND CLOSURE OF THE AA HEAP LEACH PAD AT BARRICK’S GOLDSTRIKE MINE

摘要

Barrick Goldstrike’s (Goldstrike) AA Heap LeachrnPad is an HDPE lined facility used for gold recoveryrnfrom low grade ores using conventional cyanidernheap leach technology, operated from 1987 throughrn1999. Goldstrike prepared a unique reclamation planrnfor the AA Leach Pad Facility to provide for a cost-effective,rnenvironmentally sound facility closure andrnto fulfill the State of Nevada’s closure requirements.rnTraditional Nevada leach pad closure has involvedrnrinsing to reduce cyanide concentration to anrnacceptable level, followed by reclamation. However,rncertain metals and compounds are not typicallyrnreduced by rinsing and some constituents mayrnincrease in concentration with rinsing. A closurernscenario to effect limited infiltration throughrninstallation of a capillary cover for the leach pad wasrndeveloped. The capillary cover was constructed byrnplacing a fine-grained layer above the coarse-grainedrnspent leach material to create a capillaryrnbreak. In an arid climate such as Nevada, the fine-grainedrnlayer will rarely reach full saturation and therncover will be able to store water during precipitationrnand allow removal of water through evaporation andrntranspiration (ET) during the growing season. A 1.22rnm (4 ft) cover thickness was selected as thernoptimum design cover thickness. The drainagernnetwork on the surface of the re-contoured AA HeaprnLeach Pad was specifically designed to enhance thernrevegetation, reclamation, and sediment yield controlrnaspects of the AA Heap Leach Pad closure, whilernresulting in a natural looking surface, compatiblernwith the surrounding topography. Adjacent naturalrntopographic features were used to establish targetrndesign parameters for re-contouring and erosionrncontrol design.