SYSTEM AND METHOD FOR IMPROVED LEACH STOCKPILE DRAINAGE
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.
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.