Tailing storage facilities (TSF) can have detrimental environmental consequences in their surroundings, in the hydrogeological field this happens particularly when water from the tailings infiltrate into groundwater. Even with the current technologies and evolution on tailing deposition, infiltration is expected to occur in most of the cases, and its detection represent a challenge for the operation as this process is influenced by unsaturated properties and behavior of the soil foundation that are hard to characterize and is not usually under monitoring.

This study addresses the critical challenge of understanding and managing the evolution of infiltration plumes from a specific TSF that has been under study since 2016. By employing geophysical methods, we provide an approach to assess the spatial extent and temporal dynamics of the infiltration from tailings. In this study case geoelectric methods (NanoTEM and electrical resistivity tomography) are utilized to characterize the subsurface identifying anomalies that are indicative of infiltration. These techniques offer considerable advantages over traditional monitoring methods, as they provide high-resolution data without the need for intrusive sampling, and through repeated surveys it is possible to capture the temporal evolution of the infiltration plume, revealing its migration pathways and potential effects on groundwater quality.

Our findings demonstrate the effectiveness of geophysical methods in delineating the spatial extent of the infiltration plume, identifying areas of high contaminant concentration, and assessing the potential for groundwater contamination. Moreover, the temporal analysis of the data provides valuable insights into the rate of contaminant migration and the effectiveness of mitigation measures, or after this analysis new methods or locations to control the increase of the infiltration area could be suggested.

The results of this study have important implications for the management of the TSF. By providing a comprehensive understanding of infiltration dynamics, it is possible to develop more effective strategies for preventing and mitigating groundwater contamination risks. Furthermore, the geophysical methods employed in this research offer a valuable tool for environmental monitoring and assessment.

The Environmental Qualification Resolution contemplates the monitoring of the presence and quality of groundwater downstream of the High Density Thickened Tailings (HDTT) in five monitoring wells, which are compared to process water and tailings water to identify possible infiltrations from the tailings. The monitoring well in the embankment is called MW-1 and it began to be sampled and measured in 2020. During the environmental follow-up monitoring in 2022, unexpected concentrations of certain elements were detected in the water of well MW-1, so additional studies were developed to determine if they corresponded to specific data or a trend.

In this context, geophysics was carried out to determine the origin and destination of a local infiltration in the west abutment of the embankment, specifically, through a canalization structure. Therefore, an engineering solution was implemented which consisted of the installation of a system with auxiliary drains. It was confirmed that the reported soil moisture was coming from the canalization as indicated by geophysics. Nevertheless, the field campaign continued in 2023 along with new geophysical profiles and monitoring piezometers. According to the fieldwork observations, there was a high certainty that the measurement implemented through the drains eliminated the infiltration identify in the west abutment, but it was unsure if it was related to the MW-1 results. It was proposed to perform additional fieldwork in 2024 consisting of the construction of three wells and repeating the previous geophysical profiles.

According to the interpretation of the results, high conductivity horizons were likely associated to fine grain material and/or to infiltrations recognized in the unsaturated zone (UZ). The infiltration in the drainage system in the embankment area that reached the monitoring well MW-1 was controlled in the UZ at least, given that the UZ was found to be dry. However, there might be other infiltration paths that explain the on-going unexpected values on monitoring well MW-1.

The application of an integrated hydrogeological fieldwork campaign design has proven to be helpful to identify sources of infiltrations associated with a HDTT deposit. In this case the campaign consisted in the construction of wells screened at different depths, combined with additional hydrochemistry and isotopical information obtained from the new wells has been helpful to analyzed, complement and validate the previous assumptions.

This study focuses on an abandoned tailings deposit from 1978, located on the suburb of Santiago, Chile, with insufficient mitigation measures. The tailings dam is located on the banks of the Mapocho River, the main river of the city, and less than 60 meters from a residential area, constituting a potential threat to both the environment and public health. The tailing drains directly into Mapocho River, affecting the fluvial ecosystem. Technical reports affirm the deposit partially collapsed in 1987 due to a flood of Mapocho River, releasing approximately 400,000m³ into the river and flood plains. This copper tailing deposit contains potentially toxic elements (PTEs) and exhibits potential acid drainage generation, as stated in technical evaluations. Considering the associated risks, understanding tailings accumulation zones along the river is essential.

The primary aim of this research is to study the downstream dispersion of collapsed tailings material along the river and to assess the geochemical stability of these materials. A photogeomorphological map and DEM of the area were created to identify points of tailings accumulation. Trial pits were excavated at different depths (0.15 to 2m) at several locations downstream, where samples of tailings and sediments were collected. Currently, the work is underway on granulometric measurements, geochemistry, and mineralogy of the samples. Additionally, a hydraulic sediment transport model is being implemented to evaluate areas of erosion and deposition, which will facilitate further investigation of accumulated tailings material.

Preliminary results indicate presence of oxidised tailings remnants in the surrounding area of the collapse. The tailings material displays strata in yellowish-brown, and grey hues, with a grain size predominantly comprising sands. The paste pH results ranged between 1.8-4, indicating the material has the potential to generate acid drainage. The chemical analyses revealed concentrations of Cu and Fe that exceed environmental sediment quality guidelines. Regarding the dispersed material, geomorphological analysis suggested the existence of a tailing accumulation zone on a lateral bar of the river, which was validated through a trial pit where two levels of tailings were recorded, one of them exceeding 1m in thickness at 0.8m depth.

The results indicates that tailings material has been transported and deposited in fluvial bars and floodplains, which are neither monitored nor remediated, thereby posing ecological and agricultural risks downstream. The integration of geological and hydraulic methodologies has proven effective in assessing the transport and fate of the collapsed tailings, offering replicable tools for similar case studies in Chile.

Gold mining in Colombia is a widespread industry, with operations occurring in over 15 departments and nearly 100 municipalities. In the department of Antioquia, gold mining activities are particularly prevalent in the sub-regions of Bajo Cauca and Nordeste, which collectively account for the majority of the department's gold production, making Antioquia the leading gold producer at the national level.

This research was conducted through a collaborative effort between the National University of Colombia and the University of Oviedo in Spain, utilizing materials from the "El Molino" beneficiation plant located in the municipality of Andes in the department of Antioquia. Here, the stark contrast between the gold mining operations and the surrounding agricultural landscape and coffee plantations is evident. Mining activities generate tailings composed of silica-rich crushed rock combined with processing fluids, resulting in the formation of contaminants.

In this study, gold mining sands containing refractory minerals were employed for the manufacture of clinker. The research proposed a comprehensive methodology to optimise the utilisation of these wastes, which included three primary objectives: firstly, to identify the parameters of mining waste that affect clinker manufacture; secondly, to determine the appropriate raw material proportions using Bogue's moduli; and thirdly, to compare the mechanical performance of cement produced from mining waste with that of conventional Portland cement.

The obtained results indicated that thermal pre-treatment is a crucial step in effectively reducing contaminants. However, the particle size required for an efficient reaction of silica requires a significant energy input, even though the energy consumption involved is considerably lower than would be necessary for these wastes to degrade naturally over an extended period of time The study emphasises the necessity of optimising the utilisation of waste materials, not only to enhance the efficiency of clinker production but also to mitigate the environmental impact of mining activities. The conversion of mining waste into valuable raw materials for cement production represents a significant step towards the development of more sustainable and environmentally friendly industrial practices. The results demonstrate the potential of novel approaches to waste management in the mining industry, which could lead to economic and environmental benefits.