84 1.- INTRODUCTION The transition from open-pit to underground mining has become a strategic challenge for medium and long-term mine planning. While mining remains a pillar of economic development (Jianing et al., 2024), sustained demand growth, driven by urbanization, industrial expansion, and technological change, has intensified sustainability challenges across the sector (Jiskani et al., 2022; Pouresmaieli et al., 2023). In this context, there is a growing need to incorporate sustainability criteria explicitly into strategic decisions, beyond approaches focused solely on techno-economic performance (Sahu et al., 2015). Mining impacts on the environment arise through multiple, interrelated mechanisms. In surface mining, the removal and haulage of large volumes of material typically translate into a substantial land footprint and high waste generation, whereas underground mining tends to concentrate extraction on the ore and leave a significant portion of waste rock in situ, potentially reducing the magnitude of surface intervention (Arboleda, 2017; Sahu et al., 2015). Key impacts include changes in topography and land use, habitat degradation and biodiversity loss, and effects associated with waste management and emissions, such as particulate matter, water contamination from runoff and seepage, and effluents such as acid mine drainage (Azapagic, 2004; Dasgupta et al., 2012; Richards, 2002). In areas with multiple nearby operations, these effects may be amplified through spatial accumulation and the presence of large waste disposal facilities (Richards, 2002). Further, across Latin America, accumulated social experience with mining-related socio-environmental impacts has strengthened risk perceptions and conflict, particularly in territories where water and land sustain livelihoods and local identities (BastidasOrrego et al., 2018). This context is especially significant for copper, given its importance in technologies associated with the energy transition. As extraction shifts toward deeper and larger-scale deposits, technical and socio-environmental complexity increases, reinforcing interest in operational evolution strategies, including the move from open-pit to underground mining (Badakhshan, 2023; Heydari & Osanloo, 2024). However, the literature on open-pit to underground transition decisions tends to address the problem primarily through technoeconomic and operational constraints, while socio-environmental criteria are often treated as secondary considerations or lack explicit weighting (Chung, 2016; Xu et al., 2019). This points to a methodological gap: the need for multi-criteria frameworks that can prioritize socioenvironmental variables and assign traceable weights based on expert judgment and consistent procedures. Chile provides a particularly relevant case to address this challenge. The north–central zone concentrates a large share of large-scale operations under conditions of high socioenvironmental sensitivity, shaped by structural water constraints, fragile ecosystems, nearby communities within areas of influence, and growing exposure to climate hazards (Del Rio et al., 2023; ICMM, 2019). Moreover, Chile’s role in global copper supply increases the broader relevance of its strategic decisions. Sector projections indicate national refined copper
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