1016 GUIDELINES FOR SEEPAGE ANALYSIS OF FILTERED TAILINGS DEPOSITS IN HIGHPRECIPITATION ANDEAN REGIONS V. Puyen1, A. Tello2, J. Soria3 1Ausenco Peru (victor.puyen@ausenco.com) 2Ausenco Perú (alberto.tello@ausenco.com) 3Ausenco Perú (joseph.soria@ausenco.com) ABSTRACT This study proposes a set of practical guidelines for seepage analysis in Filtered Tailings Deposits (FTD) located in regions with high annual rainfall, such as the Peruvian Andes. The research aims to properly assess the boundaries between saturated and unsaturated materials within an FTD, providing a framework for estimating piezometric levels and seepage rates that could contribute to drainage system. The proposed approach integrates the variation of the Soil–Water Characteristic Curve (SWCC) and the application a fine grained tailings facility is simulated by numerical modeling under both saturated and unsaturated conditions. The resulting guidelines define appropriate hydraulic parameters, boundary conditions, and modeling strategies for seepage assessment in filtered tailings deposits subjected to intense precipitation, contributing to safer and more sustainable FTD designs in Andean environments. KEYWORDS Filtered tailings, unsaturated soil, numerical modelling. 1. INTRODUCTION Tailings management is a critical component of mining operations, and although significant research has explored alternative uses for these materials, such applications are often limited by their physical and chemical properties and high logistical costs. One of the recent technologies is the filtered tailings, which involves the dewatering of tailings to produce a solid waste (East & Fernandez, 2021). These enhance their structural integrity and reduces the potential of environmental contamination (Ulrich & Coffin, 2013). In high-rainfall regions, tailings dams have traditionally been preferred due to established engineering practices and climatic conditions. However, regulatory and licensing changes following catastrophic tailings dam failures in Brazil have driven increased interest in alternative disposal methods, including filtered tailings and stack disposal (Garcia, Lemos, & Gomes, 2024). Filtered tailings deposits have become increasingly common since the 1990s because they offer potential improvements in safety and efficiency. Davies (2011) notes significant growth in their use, particularly in Australia, Zambia, Chile, Mexico, and the USA, as also reported by Ulrich and Coffin (2013). This technology was initially developed mainly in arid regions, where low precipitation facilitates compaction and operational performance. Despite their origins in dry climates, filtered tailings technology has expanded globally as mining operations aim to reduce water content in tailings to improve overall safety. However, applying filtered tailings deposits in high-rainfall environments challenges conventional practices, as rainfall can negatively affect compaction. These conditions introduce difficulties related to the unsaturated behavior of tailings materials and the absence of design and operational guidelines specifically developed for high-precipitation settings. Copeland et al. (2023) indicate that dry stacking is increasingly recognized as a reliable option, as it reduces failure risks, improves water conservation, lowers costs, addresses environmental concerns, and may enhance mineral recovery through additional mineral dissolution during filtration. In mining regions with high annual rainfall, the implementation of filtered tailings deposits requires careful technical assessment. Operational considerations during the rainy season are critical, as the geotechnical behavior of the stacks is strongly influenced by variability in moisture content resulting from
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