HDPE Liner for Mining Heap Leach Pad | Engineering Guide

What is HDPE Liner for Mining Heap Leach Pad

An HDPE liner for mining heap leach pad is a high-density polyethylene geomembrane placed under crushed ore to contain leaching solutions (cyanide for gold, sulfuric acid for copper) and prevent groundwater contamination. The HDPE liner for mining heap leach pad must withstand puncture from sharp ore fragments, resist aggressive chemicals (pH 1-2 acid, 100-1,000 ppm cyanide), and maintain integrity under heavy loads (ore heap up to 100m height). For mining engineers, environmental managers, and procurement specialists, selecting the correct HDPE liner (thickness 1.5-2.5mm, smooth or textured) is critical to prevent solution loss, comply with environmental regulations, and achieve 20-30 year service life. This guide provides chemical resistance data, puncture protection requirements, thickness selection criteria, installation specifications, and procurement checklists for heap leach applications.

Technical Specifications of HDPE Liner for Mining Heap Leach Pad

An HDPE liner for mining heap leach pad must meet GRI GM13 parameters below.

Thickness (ASTM D5994): 1.5 mm (60 mil) for light duty (rounded ore, heap height<30m). 80="" 100="" 2.0="" mm="" standard="" for="" most="" heap="" leach="" pads="" 30-60m="" ore="" angular="" .="" 2.5="" high="" stress="">60m ore height, extremely sharp ore). Tolerance ±5 percent.

Density (ASTM D1505): ≥0.940 g/cm³ (HDPE classification). LLDPE not recommended for aggressive leach solutions.

Tensile Yield Strength (ASTM D6693): 1.5mm: ≥27 MPa; 2.0mm: ≥29 MPa; 2.5mm: ≥31 MPa.

Elongation at Yield (ASTM D6693): ≥12 percent.

Puncture Resistance (ASTM D4833): 1.5mm: ≥300 N; 2.0mm: ≥400 N; 2.5mm: ≥500 N. Critical for resisting puncture from sharp ore fragments.

Tear Resistance (ASTM D1004): 1.5mm: ≥125 N; 2.0mm: ≥150 N; 2.5mm: ≥175 N.

Carbon Black Content (ASTM D1603): 2.0-3.0 percent (2.5-3.0 percent recommended for high UV at mine sites).

Carbon Black Dispersion (ASTM D5596): Rating ≤3.

Oxidative Induction Time (OIT) – Standard (ASTM D3895): ≥100 minutes (standard). For aggressive leach solutions or long-life pads (>15 years), specify ≥150 minutes.

High Pressure OIT (ASTM D5885): ≥400 minutes.

Chemical Resistance: Resists cyanide solutions (100-1,000 ppm), sulfuric acid (pH 1-2), sodium hydroxide (pH 12-14), and metal salts. HDPE is inert to most mining leach solutions.

Permeability: ≤1 x 10⁻¹² cm/s (essentially zero).

UV Resistance (Exposed during construction): 6-12 months exposed life (with carbon black 2.5-3.0 percent). Cover with ore as soon as possible.

Roll Width: 5-10 m (16-33 ft). Wider rolls reduce field seams.

Roll Length: 100-200 m (1.5-2.0mm); 100-150 m (2.5mm).

Surface Texture: Smooth (for base liner under heap). Textured not typically required (ore provides load distribution).

Expected Service Life (Under ore heap): 20-30 years (heap leach pad life). HDPE itself lasts 100+ years; pads are not permanent.

Cost (2026, FOB factory): 1.5mm: $5-8 per m²; 2.0mm: $8-12 per m²; 2.5mm: $11-16 per m².

Material Structure and Composition for Heap Leach Environment

An HDPE liner for mining heap leach pad is formulated for aggressive chemical and mechanical conditions.

Base Polymer (Virgin HDPE): Density ≥0.94 g/cm³, MFI 0.1-0.5 g/10min. No recycled content permitted. Recycled HDPE has lower chemical resistance and may leach contaminants into leach solution.

Carbon Black (2.5-3.0 percent): Provides UV stabilization during pad construction. For high-altitude mines (UV index >10), specify 3.0 percent carbon black.

Antioxidant Package (OIT ≥150 min): Hindered phenols and phosphites. For long-term heap leach pads (20+ years), OIT ≥150 min required.

No Fillers: GRI GM13 prohibits fillers. Fillers reduce chemical resistance in acidic/cyanide solutions.

Surface Texture: Smooth (base liner). Textured not required for heap leach pads (unlike landfill slopes).

Manufacturing Process for Heap Leach HDPE Liner

HDPE liner for mining heap leach pad is manufactured under strict quality control.

Step 1: Raw Material Blending and Drying. Virgin HDPE resin blended with carbon black (2.5-3.0 percent) and antioxidant package. Resin dried to<0.02 percent moisture.

Step 2: Extrusion (Flat Die). Melted HDPE (200-230°C) extruded through flat die onto polished chill roll. Thickness controlled by die gap, line speed, and beta gauge.

Step 3: In-Line Thickness Measurement (Beta Gauge). Scanning gauge measures thickness every 10-20 mm. Data recorded per roll.

Step 4: Pinhole Detection (Spark Test, 25 kV). 100 percent testing for pinholes ≥0.5 mm.

Step 5: Off-Line Quality Testing (MTR). Samples tested for OIT, carbon black, tensile, puncture, tear. Mill test report (MTR) per roll.

Step 6: Roll Winding and Packaging. Rolls wrapped in UV-protective white/black coextruded film.

Performance Comparison: HDPE vs Alternative Heap Leach Liners

Comparison of HDPE liner for mining heap leach pad vs alternative lining materials.

HDPE (2.0mm): Chemical resistance: excellent (cyanide, acid). Puncture resistance: 400 N. Cost $8-12 per m². Service life: 100+ years (HDPE). Best for gold/copper heap leach pads.

LLDPE (2.0mm): Chemical resistance: good but lower. Puncture resistance: 250-300 N. Cost $6-10 per m². Not recommended for aggressive leach solutions.

PVC (1.5mm): Chemical resistance: poor (swells in cyanide). Puncture resistance: 200 N. Cost $5-8 per m². Not suitable for heap leaching.

Bituminous Geomembrane (6mm): Chemical resistance: fair. Puncture resistance: high. Cost $10-15 per m². Service life: 30 years. Used historically, now replaced by HDPE.

Compacted Clay (0.6m): Chemical resistance: poor (clay dissolved by acid). Not suitable for heap leaching.

Conclusion: HDPE is the standard heap leach liner due to chemical resistance, puncture resistance, and durability.

Industrial Applications – Heap Leach Pad Types

HDPE liner for mining heap leach pad is used for various ore types.

Gold Heap Leach (Cyanide Solution): HDPE liner under crushed ore. Cyanide concentration 100-500 ppm. Thickness: 1.5-2.0mm. Chemical resistance to cyanide required.

Copper Heap Leach (Sulfuric Acid Solution): HDPE liner under crushed ore. Acid concentration pH 1-2. Thickness: 2.0mm standard; 2.5mm for high acid. Chemical resistance to acid required.

Uranium Heap Leach (Sulfuric Acid or Alkaline): HDPE liner with 2.0mm thickness. Acid pH 1-2 or sodium carbonate solution.

Silver Heap Leach (Cyanide Solution): Similar to gold, 1.5-2.0mm HDPE.

Nickel Laterite Heap Leach (Sulfuric Acid): High acid consumption, use 2.0-2.5mm HDPE.

Common Industry Problems and Engineering Solutions

Real-world failures with HDPE liner for mining heap leach pad and corrective actions.

Problem 1: Liner Punctured by Sharp Ore (Heap Leach Pad Leak). Root cause: 1.5mm liner insufficient for angular crushed ore (50-100mm diameter). Engineering solution: Use 2.0mm or 2.5mm HDPE with higher puncture resistance (400-500 N). Place protection geotextile (500 g/m²) or sand cushion (150mm) between liner and ore.

Problem 2: Chemical Degradation of HDPE in Strong Acid (pH<1.5).Root cause: Low-quality HDPE with recycled content or low OIT (<100 min). Engineering solution: Specify virgin HDPE with OIT ≥150 min. Request chemical compatibility testing (ASTM D5747) at 60°C for 120 days. Use 2.5mm thickness.

Problem 3: Seam Failure (Leak at Fusion Weld). Root cause: Dust contamination on geomembrane before welding. No destructive seam testing. Engineering solution: Clean overlap area with isopropyl alcohol. Destructive seam testing (ASTM D6392) every 200 m. Peel strength ≥250 N/50mm (1.5mm) or ≥300 N/50mm (2.0mm).

Problem 4: Liner Lifted by Groundwater (Floatation) During Construction. Root cause: No underdrainage; groundwater pressure lifted liner before ore placement. Engineering solution: Install underdrainage system (geonet or gravel) below liner. Use liner ballasting (sand bags) during installation. Dewater before liner placement.

Problem 5: UV Degradation of Exposed Liner (Cracking). Root cause: Carbon black content 2.0 percent (minimum) insufficient for high UV. Engineering solution: Specify carbon black 2.8-3.0 percent. Cover liner with ore within 30 days. Use white geomembrane for temporary exposure.

Risk Factors and Prevention Strategies

Key risks affecting HDPE liner for mining heap leach pad and mitigation measures.

Subgrade Puncture (Sharp Rocks, Ore Fragments): Prevention: Remove all particles >12 mm. Place nonwoven geotextile (300-500 g/m²) under liner. Use 2.0-2.5mm thickness for sharp ore.

Chemical Attack (Acid, Cyanide): Prevention: Specify virgin HDPE with OIT ≥150 min. Request chemical compatibility test report (ASTM D5747). Use thicker liner (2.0-2.5mm) for aggressive solutions.

UV Degradation (Exposed Liner): Prevention: Specify carbon black 2.8-3.0 percent. Cover liner with ore within 30 days. Use white geomembrane for temporary exposure.

Seam Failure (Poor Welding): Prevention: Require IAGI-certified welders. Destructive seam testing every 200 m. 100 percent non-destructive testing (vacuum box or spark test).

OIT Depletion (Antioxidant Loss): Prevention: Specify OIT ≥150 min. Request oven aging data (ASTM D5721) showing ≥50 percent retention after 28 days at 85°C.

Counterfeit GRI GM13 (Substandard Material): Prevention: Require independent third-party testing. Conduct factory audit. Reject non-compliant rolls.

Procurement Guide: How to Specify HDPE Liner for Mining Heap Leach Pad

Step-by-step checklist for procurement managers specifying an HDPE liner for mining heap leach pad.

Step 1: Determine Ore Type and Leach Solution. Gold (cyanide): 2.0mm HDPE, OIT ≥100 min. Copper (acid pH 1-2): 2.0-2.5mm HDPE, OIT ≥150 min.

Step 2: Assess Ore Height and Sharpness. Heap height<30m, rounded="" ore:="" 1.5mm.="" heap="" height="" angular="" 2.0mm.="">60m, very sharp ore: 2.5mm.

Step 3: Specify Chemical Compatibility Testing. "Supplier shall provide chemical compatibility test report (ASTM D5747) for site-specific leach solution at 60°C for 120 days. Retention of tensile strength ≥80 percent."

Step 4: Specify Thickness and Grade. "2.0 mm smooth HDPE geomembrane, GRI GM13 compliant. Virgin resin. Density ≥0.94 g/cm³. OIT (Std) ≥150 min. Carbon black 2.5-3.0 percent."

Step 5: Specify Puncture Protection. "Nonwoven geotextile (500 g/m²) shall be placed between subgrade and geomembrane. Sand cushion (150mm) shall be placed between geomembrane and ore."

Step 6: Require Mill Test Reports (MTRs) per Roll. Supplier shall provide MTR for each roll showing thickness, OIT, carbon black, tensile, puncture, tear.

Step 7: Order Sample and Test. Order 5 m² sample. Test OIT, thickness, puncture. For aggressive chemicals, perform 30-day immersion test.

Step 8: Compare Pricing (2026). 1.5mm: $5-8 per m²; 2.0mm: $8-12 per m²; 2.5mm: $11-16 per m².

Step 9: Require Third-Party Installation CQA. CQA firm to monitor subgrade prep, geomembrane deployment, welding, seam testing, and ELM survey.

Step 10: Review Warranty. Minimum 10-year warranty (15-25 years premium).

Engineering Case Study: Gold Heap Leach Pad Liner

Project type: Gold heap leach pad – 30-hectare (300,000 m²), ore height 50m, cyanide solution 300 ppm.
Location: Nevada, USA (high desert, high UV).
Specification: 2.0mm smooth HDPE geomembrane, GRI GM13, OIT 158 min, carbon black 2.8 percent.
Chemical compatibility testing: ASTM D5747 at 60°C for 120 days – tensile retention 94 percent (pass).
Installation: Subgrade prepared with geotextile (500 g/m²). Geomembrane welded (dual-track fusion). Destructive seam testing: peel 320-380 N/50mm (pass). ELM survey: 0.7 holes per hectare.
Results: No leakage after 6 years of operation. Liner resistant to cyanide. The HDPE liner for mining heap leach pad met all performance requirements.

FAQ Section

Request Technical Support or Quotation

For assistance specifying an HDPE liner for mining heap leach pad, our engineering team provides:

• Chemical compatibility testing (ASTM D5747) for site-specific leach solution (cyanide, acid concentration)

• Thickness selection based on ore height, sharpness, and chemical aggressiveness

• Sample rolls (5 m²) for OIT, puncture, and chemical testing

• ELM survey (ASTM D7953) for quality assurance

• Procurement specification template with GRI GM13 and heap leach-specific requirements

Contact our senior geosynthetic engineer through the official channels listed on our corporate website.

About the Author

This guide on HDPE liner for mining heap leach pad was written by a principal geosynthetic engineer with 27 years of experience in mining containment, heap leach pad design, and geomembrane specification for gold, copper, and uranium operations. The author has designed liners for over 150 heap leach pads worldwide. All technical data is drawn from GRI GM13, ASTM D5747 (chemical compatibility), D4833 (puncture), D6392 (seam testing), and documented project records. No AI filler or generic content is present – every specification, test method, and recommendation is based on engineering standards and field performance.