This paper investigates the overburden bed separation evolution and grouting propagation in the Menkeqing coal mine, China, using laboratory test, numerical, and field monitoring methods. Bed separation develops vertically from low-order to high-order and aligns with the mined-out area horizontally, forming stable separations in the Zhidan Formation. A comprehensive evaluation of water inrush disaster risk was conducted for the panel 11-3101. Grouting with coal gangue slurry effectively mitigated groundwater inrush and surface subsidence. Results confirm grouting as a viable measure for controlling bed-separation water inrush hazards.

The environmental assessment and management of mines in South Australia frequently relies on groundwater modelling. These models are reviewed by government hydrogeologists to ensure that the environmental impacts of mining are assessed and predicted as reliably as possible. Often government reviewers repeatedly see the same avoidable shortcomings in these models. The identification of common shortcomings is important to improve modelling and provide confidence to decision makers that a project can be responsibly developed. This is particularly important in South Australia, where groundwater resources are limited and mining is economically important. The mining and energy sector in South Australian contributed $7 billion of the state’s total $18 billion of exports in 2023. The majority of the state’s groundwater is allocated, and competition is developing even for saline groundwater in the arid northern part of the state.

To improve model assessments, five hydrogeologists from two government departments, with a combined experience of 150 years, compiled a list of common errors and omissions in mining applications and operational programs for existing mines, related to groundwater. The list is based on state, national, and international experience, with a focus on more than 40 models. Each of the five hydrogeologists identified the most common and important issues in their experience. Those that were identified by at least two of the hydrogeologists are presented here.

The following common errors and omissions were identified:

• inconsistency between the conceptual hydrogeology and its numerical model representation;
• insufficient model-independent groundwater potentiometric head maps for each aquifer to inform model boundary conditions;
• lack of consideration of groundwater dependent ecosystems;
• little focus on the damage that rising saline groundwater can cause to ecosystems in arid areas;
• sensitivity or uncertainty analysis used in place of field data or good conceptual hydrogeology; and,
• environmental compliance criteria that are linked to model predictions and are unnecessarily complex and difficult to monitor or enforce.

The findings from this review are already used in workshops with hydrogeologists working on behalf of mining companies, will be considered in mining guidelines and may contribute towards a new Australian groundwater modelling guideline. It is envisaged that by highlighting the common errors and omissions of numerical groundwater flow models to modellers and miners, models will be improved and better documented (adhering to the Australian modelling guideline). Ultimately, these will help to ensure that potential environmental impacts are reliably identified, and appropriate regulatory controls applied.

In the drive to secure the world’s supply of critical minerals, mining projects are being developed in more complex locations and at greater depth. Bulk mining methods such as caving are becoming increasingly popular to allow the production rates necessary to secure appropriate return on investment and to provide the urgently needed near term supply of critical minerals to support the energy transition. Should appropriate geotechnical conditions exist, cave mining methods can allow high production rates following a period of initial investment in substantial development required to support this mining method. Consideration of water is essential for the successful development of these types of mining operations, both to limit production risks, costs, and safety as well as to minimise or meet Environmental, Social, and Governance (ESG) targets.

When undertaking water management studies and design at deep underground cave mines, it is fundamental to consider geotechnical conditions throughout every aspect of the mine water study. In this light, we have developed a workflow to support full integration of geotechnical considerations into mine water aspects of cave mining studies. The workflow supports all aspects of a typical mine water study from site investigation through development of the Conceptual Site Model (CSM), hydrogeologic modelling, risk management, planning and engineering of the water management scheme.

Although the integration of geotechnical and hydrogeological field investigations is common practice in the industry to limit drilling costs, the key value of this study was the production of a tested workflow which allows geotechnical integration through every aspect of a cave mining focused mine water study.

The developed workflow contained in this paper is expected to be used as a checklist to guide future mine water studies supporting the development of cave mines. A case study is used as an example of the workflow, applied to advance the development of a cave mining study and demonstrating the effect and importance of geotechnical integration to the outcomes of the mine water study.

Tharisa Minerals is a chrome and platinum group metals (PGM) open-pit mine near Rustenburg, South Africa. The mine dewaters three pits and a planned underground mine. Historic workings under the mine’s active East pit also require proactive water management to ensure safe mining operations.

Tharisa’s dewatering strategy integrates stormwater control, in-pit pumping (boreholes and sumps), and pit perimeter dewatering boreholes. Automated monitoring of water levels record success in meeting drawdown targets. Water re-use enables a phased approach to zero discharge.

Tharisa is a good example of pro-active dewatering design. There are valuable insights on dewatering for surface and underground transition mines.

Monitoring data is crucial for effective resource management, as it helps validate management actions, reduce risk, and improve decision-making. However, gathering data on groundwater resources can be expensive. Focusing on targeted data collection allows for the allocation of resources toward obtaining high-value information, thus avoiding unnecessary spending on data with limited or redundant value.

This study introduces a workflow aimed at optimizing an existing groundwater monitoring program of a well-field supporting an operating mine in an arid region. The project is expected to last for several decades, with uncertainties surrounding the sustainability of the well-field yield and its potential effects on nearby environmental receptors. The current monitoring program involves collecting data from hundreds of sites, leading to substantial projected monitoring costs over time.

To evaluate how effectively collected data can reduce uncertainty in this complex, non-linear problem, we demonstrate the use of an Ensemble Variance Analysis method. This method was integrated into a multi-objective optimization framework using particle swarm optimization and the NSGA-II algorithm. The entire workflow is implemented using the open-source software PESTPP-MOU. The goal was to minimize monitoring costs while maximizing the informational value of the collected data, thereby reducing uncertainty across multiple key predictions.

The process allowed us to identify the most valuable monitoring locations and analyze the trade-offs between cost, uncertainty reduction, and the duration of the monitoring program. Results show that an 80% reduction in uncertainty is possible at just 25% of the anticipated costs of the current monitoring approach. Outcomes enabled a rationalization of the monitoring program and incurring substantial savings over the mines projected lifespan.