System and method for improved leach stockpile drainage

Abstract

Systems and methods for improving leach solution drainage in a stockpile leach operation are provided. In various embodiments, methods are provided comprising placement of a drainage measure or a system of drainage measures in a leach stockpile to improve leach solution flow through the stockpile. A system for recovery of metal values from a leach stockpile comprising a leach stockpile, a leach solution, a leach solution delivery system, a leach solution drainage system, and a leach solution recovery system are also provided.

What is claimed is: 
     
         1 . A process comprising:
 identifying a zone of low solution permeability in a leach stockpile;   placing a drainage measure in the zone of low solution permeability, wherein the drainage measure comprises a proximal terminus and a distal terminus, and wherein the drainage measure is disposed to place the proximal terminus of the drainage measure on a first side of the zone of low solution permeability and the distal terminus of the drainage measure on an opposite side of the zone of low solution permeability.   
     
     
         2 . The process of  claim 1 , wherein the drainage measure comprises a non-tubular configuration. 
     
     
         3 . The process of  claim 1 , wherein the drainage measure is physically separate from a leach solution distribution system. 
     
     
         4 . The process of  claim 1 , wherein the zone of low solution permeability is identified by at least one of identifying a zone of saturation, identifying a zone of increased material density, and performing core penetration testing. 
     
     
         5 . The process of  claim 1 , wherein the drainage measure is placed in the leach stockpile following leaching of at least a portion of the leach stockpile. 
     
     
         6 . The process of  claim 1 , wherein placing a drainage measure in the zone of low solution permeability reduces a hydraulic pressure of the leach solution in the leach stockpile. 
     
     
         7 . A process for producing enhanced leach solution drainage in a leach stockpile comprising:
 delivering a leach solution to a leach stockpile with a leach solution delivery system;   applying the leach solution to at least a portion of the leach stockpile; and   installing a drainage measure in a leach stockpile;   wherein the drainage measure is selected from a group consisting of: wick drains, pipe drains, perforated pipe drains, sheet drains, strip drains, chimney drains, combination drains, drain holes, and pumps;   wherein the drainage measure is physically separate from the leach solution delivery system; and   wherein the drainage measure is physically separate from a leach solution collection system.   
     
     
         8 . The process of  claim 7 , further comprising applying the leach solution to at least a portion of the leach stockpile to produce a partially leached stockpile and installing the drainage measure in the partially leached stockpile. 
     
     
         9 . The process of  claim 7 , wherein installation of the drainage measure decreases a moisture content of a first region of the leach stockpile adjacent to a first portion of the drainage measure. 
     
     
         10 . The process of  claim 7 , wherein installation of the drainage measure produces solution transfer from a first region of the leach stockpile to a second region of the leach stockpile. 
     
     
         11 . The process of  claim 10 , wherein the first region has a higher moisture content than the second region. 
     
     
         12 . The process of  claim 11 , wherein the first region and the second region are separated by a zone of low solution permeability. 
     
     
         13 . The process of  claim 12 , wherein solution transfer to the second region produces increased leaching of metal values from a metal-bearing stockpile material in the second region. 
     
     
         14 . The process of  claim 7 , further comprising installing a system of drainage measures in the leach stockpile. 
     
     
         15 . The process of  claim 14 , wherein the system of drainage measures comprises a plurality of wick drains installed substantially vertically in the leach stockpile and wherein the plurality of wick drains are arranged in a predetermined configuration across the leach stockpile based on hydraulic properties of a stockpile material. 
     
     
         16 . The process of  claim 15 , wherein the plurality of wick drains are installed in an order based on identification of at least one of a zone of saturation or a zone of low solution permeability in the leach stockpile, and wherein the order comprises preferentially placing a wick drain at the at least one identified zone. 
     
     
         17 . A system for recovery of metal values from a leach stockpile comprising:
 a leach stockpile comprising a plurality of stockpile lifts;   a leach solution;   a leach solution delivery system coupled to the leach solution and configured to deliver the leach solution to the leach stockpile;   a leach solution drainage system disposed in the leach stockpile and configured to facilitate leach solution transfer across zones of decreased leach solution permeability; and   a leach solution collection system disposed at the bottom of the leach stockpile and configured to collect pregnant leach solution flowing out of the leach stockpile.   
     
     
         18 . The system of  claim 17 , wherein the leach solution drainage system comprises a plurality of wick drains. 
     
     
         19 . The system of  claim 18 , wherein at least one of the plurality of wick drains is configured to facilitate leach solution transfer between a first stockpile lift and a second stockpile lift. 
     
     
         20 . The system of  claim 18 , wherein the plurality of wick drains are disposed substantially vertically in the leach stockpile and wherein each of the plurality of wick drains is configured to extend from a top surface of the leach stockpile into a bottom lift of the leach stockpile.