<![CDATA[Material availability is essential for underground mining operations; however, fragmented storage, limited inventory visibility, and delivery delays can disrupt production and increase operational waste. This study aimed to identify the root causes of inventory control and storage management issues for ground support materials at the Grasberg Block Cave, Kucing Liar, and Deep Mill Level Zone mines of PT Freeport Indonesia and to formulate prioritized improvement strategies. A case study approach was conducted using the Lean Six Sigma DMAIC framework, incorporating observations, 5S assessments, questionnaires, semi-structured interviews, operational records, Value Stream Mapping, Pareto analysis, Current Reality Tree analysis, Action Priority Matrix, and Impact-Complexity Analysis. The findings showed that waiting was the dominant waste, with a score of 115, followed by inventory waste with a score of 98; together, these two categories accounted for 44.9% of the identified waste. Six of seven storage locations were rated as fair or poor. Four root causes were identified: the absence of standardized inventory management, inadequate control and staffing in shadow storage areas, weak storage and 5S standards, and limited availability of transportation equipment. Dedicated storemen achieved the highest Impact-Complexity Ratio score of 3.23, followed by 5S compliance at 2.59 and daily inventory reporting at 1.91. The study concludes that implementing these initiatives can strengthen traceability, accessibility, inventory accuracy, and material flow reliability across mining operations.]]>
