Looking back over 50 years of studying acid mine drainage and the mineral deposits and mining activities that produce it, several lessons that should be universally recognized are often not.

(1) Conceptualization of a mine site begins with one’s background and experience with geology, hydrology, natural water chemistry, microbiology, mining, and mineral processing. Because these are typically not courses covered by civil engineering curricula, consulting companies, mining companies, and regulatory agencies must either hire this expertise or learn these skills through training. Progress has been made in this direction, but more is needed. If the conceptualization of a site is inadequate, costly mistakes are inevitable.

(2) Characterization of a site requires some of the same skill set and includes detailed knowledge of best practices for sampling procedures, time and costs needed to do adequate characterization, how to incorporate data into a site model that addresses fluxes and reservoirs of contaminant substances. Water analyses should be “reasonably” complete with major ions, trace elements, redox species, and preferably a few relevant isotopes. Seasonal trends and storm event trends should be sampled to determine how precipitation events and change of seasons affects aqueous contaminant mobility.

(3) Modeling is often a guessing activity full of assumptions and misconceptions that become clearer and improved through hypothesis testing and further data collection. The type of models, the inherent assumptions, their limitations, and the codes used to implement the models should all be transparent to the stakeholders. Sometimes nothing beyond a conceptual model is needed for a site, and sometimes a site can be so complex that different models should be developed, and the experts should discuss dissimilar conclusions and plot a path forward that clears up any controversial concerns.

Specific examples will be presented from actual case studies that emphasize these factors including the study of "natural background." Of all the skill sets, one of the most important is a solid knowledge of natural and man-made water contaminants and how water interacts with minerals and waste materials. Along with that knowledge, an expert should be humble enough to recognize that these sites are very complex and can perplex even the best experts, requiring a cautious iterative approach to find the most cost-efficient remediation.

This study addresses a critical environmental challenge, Acid Mine Drainage (AMD) in pit lakes, by exploring the potential of fly ash (FA) as a neutralizing agent. AMD in open-pit mines creates acidic water bodies that threaten ecosystems, demanding innovative and cost-effective treatment solutions. Fly ash, a coal combustion byproduct with alkaline properties, offers a promising alternative for in-situ neutralization of AMD, with the added benefit of better FA waste management practices. This research investigates the settling characteristics and physic-geochemical stability of FA when applied to neutralize AMD.

A novel aspect of this study is the usage of FA for AMD treatment and also its focus on controlled laboratory experiments using acrylic tubes containing different volumes of AMD (5, 10, and 15 liters), which simulate varying depths in pit lakes while maintaining a consistent FA-to-water ratio of 1:5. During a 24-hour settling period, FA’s behavior in AMD was analyzed by observing settling velocity, particle stratification, and pH change. Post-treatment water samples underwent Ion Chromatography (IC) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) analyses, with geochemical modeling conducted using PHREEQC software to understand secondary mineral formation and long-term stability.

The results showed significant improvements in water quality, with pH levels increasing from 2.77 to 6.24, 6.81, and 7.65 in the three acrylic tubes. Fe and Al concentrations decreased by over 100%, while manganese levels dropped by 19.88% to 40.06%, demonstrating FA’s effectiveness as a neutralizing agent for AMD. Notably, pH levels improved to near-neutral within the first hour and remained stable over the next 24 hours. The contact time between FA and AMD was directly proportional to water quality improvement, as smaller FA particles with larger surface areas took longer to settle. Settling velocities of FA particles ranged from 15.38 to 21.88 cm/s. Following neutralization, iron precipitated as goethite (FeOOH), hematite (Fe₂O₃), and hydrohematite; aluminum precipitated as gibbsite (Al(OH)₃); and manganese as pyrolusite (Mn(OH)₂) and manganite (MnOOH).

This research implies that FA can serve as an effective, sustainable solution for AMD neutralization, offering both a feasible treatment method and an environmentally beneficial use for FA waste. Implementing FA as a treatment agent in pit lakes could substantially enhance AMD-affected water bodies, aligning with broader environmental management goals for mining operations.

At a coal mine in north-eastern British Columbia, Canada, three lysimeters were constructed to evaluate the relative performance of covers placed on run of mine rock as a mitigation option. Mine rock covers are required as part of the approved reclamation plan for the coal mine, therefore progressive reclamation, including application of covers, is being contemplated to mitigate contaminant loadings at the site.

Each lysimeter consists of a 5 m tall mine rock pile built on a 17 m x 17 m pad, complete with liner systems, a network of collection pipes, and containment berms. Any percolation through the surface of the bare or covered mine rock pile is piped to a collection system where water volumes are measured, and water quality samples can routinely be taken. Regarding placed materials and cover systems: Lysimeter 1 (L1) is a control pile, Lysimeter 2 (L2) has a soil reclamation cover, whereas Lysimeter 3 (L3) has an engineered soil cover.

Data collected thus far confirms the research hypothesis that percolation through the L3 lysimeter is systematically lower than at L1 and L2, while noting that much of the total seepage measured at all three lysimeters is attributed to relatively infrequent, but high magnitude, convective rainfall events (>30 mm/day). Consistent with initial research hypotheses, seepage at L2 lysimeter was also typically less than L1 lysimeter (i.e., 90% of the time). However, measured seepage at L2 following extreme rainfall events was routinely higher than at L1, and in aggregate, total seepage at L2 and L1 was essentially the same over the study period. Since 2019, sulfate and selenium concentrations have consistently been highest at L1 lysimeter, lowest at L2 lysimeter, but intermediate at L3 lysimeter.

Study outcomes will eventually be used to inform site reclamation planning, in keeping with best management practices for mitigating contaminants of concern at the mine site. To date, the uncovered L1 lysimeter is characterized by high runoff volumes and elevated seepage concentrations for key parameters (e.g., sulphate and selenium) when compared to L2 and L3 lysimeters which are covered. Contaminant loading from L2 and L3 lysimeters is lower than at L1, but conclusions are mixed at L2 and L3 in terms of overall performance: L2 lysimeter yields higher runoff volumes compared to L3, but seepage concentrations at L2 are lower than at L3 lysimeter.

Around the world, both mining and underground civil works require excavating tunnels or ramps, whether for access, ore mining, rail or road connectivity, ventilation, water supply, among many other applications. During this process, it is common to find groundwater, which must necessarily be removed to achieve the final objectives of the excavation.

If the slope of the tunnel or ramp is positive or zero, drainage can be done through a lateral channel or pipe without major impacts. However, when the slope of the ramp or tunnel is negative, the water must be removed as soon as possible to avoid its accumulation, always overcoming gravity. It is common that when the depth reached exceeds the hydraulic capacities of a simple pumping system, pumping stations must be used to drain the water in stages to the surface or to the final accumulation or drainage site.

This paper develops a methodology for the design, sizing and planning of pumping stations for underground drainage in mines with depths that require the use of pumping stations, due to the high hydraulic pressures required by a pumping system above 10 bar. The methodology consists of the use of hydraulic design variables for the system that are initially proposed, according to the maximum expected infiltration flow and the maximum depth that would be reached in the project. With the latter, and the total head losses estimated by the proposed design variables, the total head loss to be overcome is determined and then subdivided according to the number of pumping stations proposed based on the height and flow to be overcome by each one.

The application of this methodology efficiently takes advantage of available resources, maintenance, geological conditions of the site and drainage needs in terms of flow and depth, considering potential anomalous situations and response capacities in the event of emergencies or faults. It also allows the treatment and reuse of water to be used as "industrial water". This methodology can be used for all types of underground works, whether civil, mining, military or others that require the management and use of water resources found underground during the excavation process and/or in its subsequent operation.

The importance of this work lies in addressing the increasing risks posed by dams, whose failures have led to environmental disasters, operational disruptions, safety issues and security problems that put lives and the population close to the mining operation at risk. The mining industry faces increasing pressure to monitor these dams more effectively, especially given their proximity to communities. This paper emphasizes the need for strict real-time monitoring systems to manage geotechnical risks and prevent structural failures, ensuring the safety of both personnel and nearby populations. Using advanced technology to improve risk management in mining operations is critical to mitigating potential catastrophes.

What sets this approach apart is the integration of 3D laser scanning technology with dedicated software. This novel method provides continuous monitoring and real-time data reporting on changes in the dam surface and stability. The system can detect minute deformations, track moisture levels and alert engineers to any potential risks. Furthermore, the technology allows for the creation of new monitoring zones after initial scans, enabling adaptive risk management even in areas that were previously unmonitored. This flexibility and the system’s ability to perform retrospective analysis make it an advanced tool for predictive and preventative monitoring.

In this study, an innovative and precise remote monitoring system for tailings dam stability control was implemented using a combination of 3D laser scanners and software that processes point cloud data using Gaussian weighting. The system was able to capture detailed data on dam walls, allowing geotechnical engineers to analyze deformation patterns and predict potential areas of failure. It also provided real-time alerts for immediate action when critical changes are detected. The method demonstrated the system’s ability to track millimeter-level movements and offered flexible visualization and reporting options to suit various operational needs. Being able to recreate failure scenarios and critical areas for re-evaluating situations and decision making is key to geotechnical tasks in tailings stability.

The key findings show that this innovative control system is a cost-effective and flexible solution for tailings dam monitoring. Its applications extend beyond safety monitoring, as the system can be used for routine operational measurements and risk assessments in mining. The implications of this work highlight the importance of advanced monitoring technologies to improve safety and operational efficiency in the mining sector, while also addressing environmental concerns related to dam failures.