La Arena

1. Project Overview

La Arena is a mining operation located in northern Peru, approximately 480 km north-northwest of Lima. The project is distinguished by its dual geological setting, comprising two distinct types of mineral deposits:

• High-sulfidation epithermal gold mineralization hosted in oxidized breccias within sandstones of the Chimú Formation.

• Copper and gold sulfide mineralization associated with multi-phase porphyry intrusions.

2. Project Challenges

The development and operation of La Arena presented significant technical and operational challenges, including:

• The presence of gold oxides with elevated copper content, requiring specialized metallurgical and processing solutions.

• The staged expansion of the heap leach pad (Phases 3B, 4A, 4B, 4C, and 5) and waste rock dumps (Waste Dump 2 and East Waste Dump).

• The project’s location in a high-seismicity region, necessitating 3D dynamic stability evaluations to ensure the integrity of critical mining facilities.

• Continuous updates to the water management system to accommodate ongoing expansions and infrastructure modifications.

• Development of Organic Material Deposits (OMDs), designed to meet stability and environmental performance criteria for future closure use.

• Securing permits for multiple expansions, including submission of the Third MEIA (Modification of the Environmental Impact Assessment).

3. Our Approach and Solutions

To address these challenges, Anddes implemented an integrated engineering strategy that included:

• Geomechanical analyses and slope design for the Calaorco and Norte open pits.

• Sequential development of basic and detailed engineering for the various heap leach pad and waste dump expansion phases.

• 3D dynamic stability assessment of the heap leach pad under both operational and closure conditions.

• Ongoing updates and optimization of the water management system.

• Periodic site visits, review of geotechnical instrumentation data, and preparation of inspection and monitoring manuals.

• Implementation of Construction Quality Assurance and Control (CQA/CQC) programs for earthworks and geosynthetic installation.

• Development of innovative solutions, such as the 8-hectare dynamic leach pad constructed over the existing pad footprint, optimizing the use of available space.

4. Results Achieved

The implementation of these solutions delivered significant operational and strategic outcomes:

• Expansion of multiple heap leach pad phases enabled efficient processing of gold oxides with elevated copper content.

• 3D dynamic analyses confirmed heap leach pad stability under both operating and closure scenarios.

• Sequential design of waste rock dumps and OMDs optimized waste rock and organic material management.

• Continuous improvements to the water management system minimized environmental impacts.

• Preparation of targeted basic engineering packages supported timely regulatory approvals for expansions.

• Updated seismic hazard assessments and slope risk evaluations enhanced the safe operation of open pits.