Improving Productivity and Operational Efficiency in Overburden Removal at a Nickel Mine Using a Lean Six Sigma Integration Approach

Abstract

The increasing global demand for nickel, driven by the rapid expansion of electric vehicle battery production and the clean energy transition, has intensified the need for highly efficient mining operations. Overburden removal represents a critical stage in nickel mining because its productivity directly affects ore extraction continuity and overall operational performance. However, PT X, a nickel mining contractor in Southeast Sulawesi, has consistently failed to achieve its overburden productivity target of 280 BCM/hour, resulting in increased operational costs and substantial financial losses. This study aimed to improve productivity and operational efficiency in overburden removal by integrating the Lean Six Sigma approach with the DMAIC framework, Failure Mode and Effects Analysis (FMEA), and Fault Tree Analysis (FTA). A mixed-method case study approach was employed using operational data collected from January 2024 to July 2025, supplemented by field observations and Focus Group Discussions (FGDs). The findings showed that 51.4% of total productivity losses were attributed to controllable delays. FMEA identified Repair Front (RPN = 400), Repair Disposal/Dumping Point (RPN = 200), and Road Maintenance (RPN = 144) as the highest-priority risks, while FTA traced these failures to deficiencies in operational supervision, equipment availability, quarry material supply, and geotechnical conditions. Improvement strategies developed through FGDs included optimizing equipment allocation, strengthening preventive maintenance practices, improving drainage systems, enhancing supervisory procedures, and reinforcing cross-functional coordination. Economic evaluation indicated that the proposed mitigation strategies were feasible, producing a Benefit-Cost Ratio (BCR) of 1.53. The integration of Lean Six Sigma, FMEA, and FTA provided a systematic and sustainable framework for reducing operational waste, minimizing process variation, and improving productivity in nickel mining operations.