The key to a successful heap leach application, is to maximise the recovery of leachate whilst minimising contaminant risk to the environment. Geosynthetic lining and drainage collection systems are the preferred option to ensure that returns are maximised and regulatory requirements are met.

GEOFABRICS EXPERTISE IN HEAP LEACH

Geofabric Australasia’s heap leach solutions include Polymeric Geomembrane lining systems, geotextiles for geomembrane protection and Drainage systems that include Geocomposites and Megaflo Panel Drains. These inevitably require pre-qualification through our GRID R&D Laboratory, to ensure the selected materials are not compromised by the project chemistry and environment.

Heap leach systems are becoming more refined in recent years, to ensure maximum recovery of target metals and less waste generation and contaminant risk. Traditional design observed significant Geosynthetic challenges due to the lack of compatibility between geosynthetic materials (e.g. geomembrane, geopipe, geotextile, etc), native materials, ore, and operational conditions/restrictions. This issue becomes more pronounced as heap leach pads are constructed in steep terrain, harsh climates (wet, cold, etc), and subjected to high ore loads (exceeding 4 MPa). The traditional heap leach pad liner system has comprised a composite soil and geomembrane liner system with a mineral drainage layer for gravity solution flow to external ditches and ponds. 

A superior Heap Leach lining system is a Geomembrane and geosynthetic clay liner (GCL) composite liner to achieve the lowest leakage rates under high operating heads. This lining system is only a better option if it is demonstrated as compatible to the heap leach chemistry but also designed to accommodate the elevated stresses created by the placement and depth of the ore above.

Geofabrics offers the GRID Laboratory to partner with asset owners and designers to ensure the suitable selection of Geomembrane Liner, protection Geosynthetics to ensure survivability and the most efficient drainage system for pregnant leach recovery. The team has also developed innovative techniques for future leach treatment barriers and repurposing of legacy tailings.
 

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Heap Leach

HEAP LEACH LINING SYSTEMS

Heap Leach systems generate aggressive liquors over large footprints that present significant risk to traditional earth lining systems. The consistency of a Quality Controlled Geomembrane that can be pre-qualified with specific site testing presents the optimum lining solution that can be demonstrated with suitable longevity.

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FEATURED PRODUCT

Geomembrane Liners

Heap Leach systems generate aggressive liquors over large footprints that present significant risk to traditional earth lining systems. The consistency of a Quality Controlled Geomembrane that can be pre-qualified with specific site testing presents the optimum lining solution that can be demonstrated with suitable longevity. Once qualified by immersion testing, the geomembrane should be chosen in consideration of the stresses created by differential subgrade settlement,  and the point load impacts of the granular ore above during installation and over the long term.

Geofabrics Geomembranes can include Polyethylene liner, specialist polymer Cooley Liners or Terenap Bituminous Geomembranes according to the site chemistry and robustness required.

Geosynthetic Clay Liners

The traditional heap leach pad liner is a composite soil and geomembrane liner system but a Geosynthetic Clay Liners (GCL) presents as a technically better composite liner than standard soils. These products are select polymer geotextile outer layers needled punched to each other to ensure shear strength with a uniform core of premium quality powdered sodium bentonite to provide the hydraulic barrier. Geofabrics ELCOSEAL® GCL’s can reduce contaminant transport and help achieve environmental compliance but only if the bentonite contained in the GCL is pre-qualified with the leach chemistry to ensure maximum performance.

Geotextile filters - Geofabrics bidim® or Texcel

The choice of Geotextile will depend on the pregnant liquor impacts on the polymer, and mechanical damage risks of the project stresses and environment.

The first choice to maximise costs is a bidim® polyester, continuous filament, non-woven, needle-punched geotextile, with a high strength to mass ratio. bidim® is manufactured to the highest quality control standards from both virgin and recycled polymer depending on the site chemistry.

Texcel Staple Fibre Geotextiles are an alternative that can be manufactured in both Polyester and Polypropylene according to the damage risks, but also according to the site chemistry risk on polymer degradation. Testing the Geotextile to match the project conditions is a must for Heap Leach applications, the Geofabrics GRID Laboratory links has techniques to ensure that the Geotextile can serve as a filter, protection layer to the environment over the project design life.
 

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Heap Leach Systems

HEAP LEACH DRAINAGE SYSTEMS

The primary function of the drainage system is to maximise leach recovery but it also serves an important function to prevent heads acting directly on the lining system. Traditional aggregate is often expensive to import and install over a large footprint, but a well designed Drainage Geocomposite or Geofabrics Megaflo Panel Drain often designed in combination, can accommodate high loads and maintain known volume performance under high loads for the required design life.

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Featured Products

Geocomposite or Megaflo Heap Leach Drainage Systems

The primary function of the drainage system is to maximise leach recovery but it also serves an important function to prevent heads acting directly on the lining system. Traditional aggregate is often expensive to import and install over a large footprint, but a well designed Drainage Geocomposite or Megaflo Panel Drain often designed in combination, can accommodate high loads and maintain known volume performance under high loads for the required design life. 

Trinet triaxial geonets provide a cost effective alternative to traditional gravel drainage layers under increased stresses. The heavy duty geonet provides high flow rates under high confining stresses due to the three dimensional structure’s ability maintain a stable shape which resists crushing. The Trinet can be manufactured with select Geotextiles and serve an important function of liner protection but must be demonstrated by performance testing. The Geofabrics GRID Laboratory has direct testing and project expertise for the design and testing of Geocomposite Drains under high loads to analyse their cushion benefit and drainage performance under high loads.

Megaflo Drainage

Megaflo® is a geocomposite flat panel drainage system, combining an inert HDPE core and geotextile filter sock.  Megaflo® provides the most efficient drainage system for Heap Leach applications because it can be installed directly onto the Lining System, round pipes are installed mid aggregate above making them far less efficient. Megaflo® is able to resist large vertical loading encountered but must be pre-qualified to the project stresses, properly designed systems have proven effective under fill depths of up to 100m as demonstrated by FEA modelling.

Megaflo® is ideally suited for remedial drainage is available in Standard and Ultra grade and also Recyled and Virgin polymer according to the project need. Please consult the Geofabrics technical team to ensure the maximum technical benefit is specified to achieve the highest cost benefit.

TenCate Geotubes in Heap Leach

TenCate Geotube® dewatering and containment technology is well suited for dewatering legacy tailings dams, and other sludges that still contain precious metals. By capturing and containing valuable metals using TenCate Geotube® containers, the expense of treating mine waste can be offset, polished water can be generated, and both become a valuable income stream. This is an important option for Tailings repurposing functions, where a return can be generated rapidly prior to full production implementation.