Acid mine drainage and waste dispersion in legacy mining sites: An integrated approach using UAV photogrammetry and geospatial analysis

Abandoned mines pose environmental risks due to the accumulation of sulfide-rich waste, which generates acid mine drainage and produces fine-grained, unconsolidated materials that, when deposited on steep slopes, accelerate erosion and contaminant transport. This study assesses the environmental impact of the Trimpancho mining complex by integrating UAV-based photogrammetry, water analysis, and mine waste characterization. Aerial surveys produced high-resolution orthomosaics and digital surface models, enabling the identification of runoff patterns, erosion hotspots, and waste accumulation. The estimated waste volume is approximately 253,377 m³ . Key findings highlight critical erosion areas on steep slopes (>30°) where waste mobilization enhances metal and sulfate transport into the Trimpancho stream, affecting the Chança River. Water samples have pH values ranging from 2.59 to 8.27, electrical conductivity peaking at 4171 µS/cm, and elevated concentrations of iron (65.7 mg/L), aluminum (174 mg/L), manganese (23.5 mg/L), and zinc (20.7 mg/L). Mine waste characterization revealed that Nuestra Señora del Carmen dump exhibited higher leaching potential compared to Volta Falsa. This study underscores the value of UAV technology for cost-effective and high-resolution environmental monitoring in abandoned mines. The results emphasize the need for targeted remediation strategies and water quality improvement. This multi method approach can serve as a model for assessing contamination risks and optimizing environmental monitoring programs in other legacy mining sites.