2025 – Catoca Diamond Mine – implementation of an advanced monitoring network for a Tailings Storage Facility.
Abstract
The Catoca mine is an open-pit diamond mine belonging to Sociedade Mineira do Catoca in Angola that began in 1995, when the first researchers arrived at the Catoca kimberlite to prospect the area, with exploration activities beginning in 1997. The mine is located in the Province of Lunda Sul, 1050 km east of Luanda, capital of the Republic of Angola.
It has a large active tailings storage facility (TSF) and two smaller deactivated TSFs. Over the last three years, Sociedade Mineira do Catoca has installed a comprehensive and large monitoring and control network infrastructure that is fully automated and connected to a database and dashboard viewed by operators and managers at remote workstations. This interactive database can be accessed anywhere in the world. With this interactive database, Angola now has an enhanced monitoring network capable of analysing the causes of TSF failures and providing early warnings to help prevent them.
The monitoring network is the first in Angola and is state-of-the-art for modern TSF monitoring, in line with the principles of the Global Industry Standard for Tailings Management (GISTM). The network integrates the monitoring of water levels, length of beaches behind the different dikes, pore pressures, slope movement, and weather information and is linked to an alert system that not only tracks movement but also the causes of the movement of a TSF.
The installation of monitoring equipment and the systematic management of data enables detailed control over a TSF, improving risk assessment and overall safety. Project management and installation sequences can be replicated for other mines.
The main applications are good examples of what can be achieved for the post-construction implementation of detailed monitoring for active and decommissioned TSFs in remote areas. The implications are that the strategy and network can be used to improve safety and manage risk on other mines around the world. The facility is an excellent example of engineering collaboration, geotechnical interpretation, instrumentation design, and software connectivity.
Keywords: Tailings Storage Facilities, Monitoring, Pore Pressures, Dam Failure, Diamond Mine
2025 – Advances in integrated performance monitoring of Tailings Storage Facilities.
Abstract
Since the initiation of the Global Industry Standard on Tailings Management (GISTM), the adoption of advanced monitoring technologies has expanded. These systems utilize continuous, near-real-time data from diverse sensors, integrating geotechnical, hydrological, and environmental measurements.
Enhanced by real-time data fusion and advanced statistical analysis, the technology supports detecting subtle structural deviations, improving the accuracy of quantitative risk assessments, and reducing false positives. Dynamic, tailored response plans are activated based on detected anomalies, enabling swift, informed decision-making. This approach enhances safety and proactive risk management for tailings dams and promotes regulatory compliance, operational efficiency, and sustainability. Keywords: GISTM; Tailings Management; Advanced Analytics, Sustainability
2025 – Advances in mine dewatering design and monitoring at Tharisa chrome mine Rustenburg South Africa.
Abstract
Tharisa Minerals operates a large chrome and platinum group metals (PGM) open pit mine near Rustenburg, situated in the western limb of the Bushveld Complex, which holds over 70% of the world’s platinum and chrome resources. Tharisa mines and processes five MG chromite layers. Despite the region’s low rainfall, the mine must dewater its three pits and planned underground mine ahead of mining operations.
The proximity to old underground mining voids in the eastern side wall of the East pit means the mine has to manage its water in advance of mining to ensure risk free ore extraction.
The dewatering strategy comprises: accurate stormwater control, the use of in-pit and pit-perimeter dewatering boreholes, and sump pumping. The locations of the dewatering boreholes were determined using geophysical surveys, achieving a 100% success rate. Conceptual and numerical models were developed to optimize borehole placement and estimate the water volumes that need to be removed to maintain targeted water levels. A detailed, automated monitoring network is used to manage the water and show the effect of pumping on water levels for specific sectors of the mine.
Main findings are the importance of early and well-maintained storm water controls coupled with early installation of in-pit and pit perimeter dewatering boreholes. The effect of the flooded neighbouring and underlying mine has to be managed in advance to ensure the ore can be accessed in all seasons. The utilisation of as much water as possible in the plant reduces the release of water to the environment and moves towards a zero-discharge strategy.
Tharisa mine is a good example of how a dewatering design can be implemented once mining has started and shows the cost effectiveness of a phased approach to mine dewatering design. This case study provides valuable insights to all surface and surface to underground transition mines.
Keywords: Chrome, Dewatering, Pit-Perimeter, Monitoring, In-Pit Pumping, PGMs
2024 – A phased approach to mine dewatering – updated from IMWA 1993.
Abstract
Mining often requires penetrating the local and regional water table. This creates inflows, which if the area is wet and the country rock highly permeable, becomes at best a nuisance to operations and at worst an extreme hazard. Effective dewatering creates dry working conditions which are preferable as they reduce risk, reduce wear and tear on machinery, reduce earth moving costs, improve slope stability for open pits and therefore improve safety.
Dewatering success is directly linked to a detailed understanding of the groundwater regime enabling application of the best strategy to intercept groundwater inflows. Options available are both passive and active methods including detailed stormwater design, drainage trenches, drain-holes, pit-perimeter pumping boreholes (wells), in-pit boreholes, sumps, dewatering galleries, or a combination of methods. A phased approach assists with logically managing the data, information and knowledge for use in dewatering design and implementation. Keywords: Mine dewatering, conceptualisation, numerical modelling, dewatering methods, dewatering scenarios.
The potential effects of groundwater inflows should be assessed at the pre-feasibility stage but can be done at any stage of the mine life. A hydrogeological investigation is best tackled in three phases. The first phase is a desktop study to identify the problem, collect site data, create a detailed initial conceptual hydrogeological model then use the information to identify the most practical options for water control.
Phase 2 comprises numerical modelling of the conceptualisation, supported with accurate and interpreted monitoring data. The objective is to use predictive simulations of dewatering options to determine the best strategy for water control. Phase 3 sets dewatering targets to support the mine design, creates an initial dewatering design then implements a prototype to test the concept. Success is evaluated, and the design improved to increase efficiencies and enable full implementation. The phased approach is iterative as the conceptual and numerical models are regularly updated, recalibrated with the latest monitoring information, and used to review and implement the dewatering strategy. The monitoring network is continually improved, and the phased approach repeated annually to ensure water control objectives are met for each stage of mining. This paper is an update of the IMWA paper Morton et al. (1993) which is still widely read.
2023 – What lies beneath – the use of thermal imagery and satellite data to observe tailings seepage and water risk and pre-empt failures.
Abstract
The monitoring of movement of a tailings storage facility (TSF) is often too late to stop failure. Most failures are caused by the presence of water. Monitoring of the water level in the pond and the pore water in a TSF dam wall enables early warning of potential failures. Water pressure can be measured using vibrating wire piezometers and the occurrence of seepage zones can be detected using thermal imagery.
Thermal imagery is a well-known technique for viewing ‘wet’ and ‘dry’ rocks. KLMCS used airborne thermal imagery in the 2000s to plot ground water occurrence for the Anglo American, Debswana and De Beers mines. Aerial surveys covered large areas and were used to observe seepage from the TSFs. Satellite data has also been used to plot TSF seepage on a smaller scale. Images from Maryland University are available for free and can be plotted as a first pass to assess if airborne surveys are worth the extra expenditure. Modern drones can carry thermal scanners and can be used at less expense than fixed wing platforms. Geophysical techniques can also be used to determine what lies beneath the face of a TSF. The paper shows examples from each method and provides images from each type of survey.
2023 – Advanced monitoring of Tailings Storage Facilities and dams to prevent failure.
Abstract
Following the publication of the Global International Standard for Tailings Management (GISTM) many different types of monitoring network have been launched for use in the de-risking of Tailings Storage Facilities (TSF). Management of risk depends on using accurate data that is translated into information, then knowledge. Very fast data transmission coupled to real-time bespoke dashboards have become a significant tool for risk reduction.
This paper summarises the monitoring networks available and ranks them for effectiveness in preventing failures.
The main finding is that the best monitoring systems include measurement of the factors behind causes of failure, such as measurement of hydraulic pressures and their speed of change both beneath and around TSF’s and dam walls. Groundwater monitoring is an important component for risk management. Linkage to cost effectiveness encourages the systems to be installed and contribute to TSF management. Automation reduces human error. Recalculation of Safety Factors is possible and can be frequently updated.
The essential components of TSF risk reduction are discussed and a blueprint for accurate risk management with practical outcomes is presented. Techniques such as real time geo-resistivity profiling are illustrated. Case studies from Europe (Keilder Water), Africa and South America (El Soldado) are given and the future of TSF monitoring is discussed.
This work will be very useful to TSF managers and all those involved in promoting the safety of TSF’s in all types of climates and terrain. Transparency in information sharing and the international dissemination of TSF health to shareholders, stakeholders, communities and insurers can become routine.
Keywords: Tailings storage facilities (TSF), global international standard for tailings
management (GISTM), monitoring, risk, pressures, failure
2023 – Structural logging and modelling for use in simulation of inflows in underground hard rock mines.
Abstract
African mines are predominately located in hard rock. Inflows to the underground or surface workings are typically along geological structures. Often the matrix permeability of the country rock is very low, individual water bearing structures provide some 80% of the inflows. It is therefore very important to map geological structures and plot the sources of water flowing into the mine.
Fractured rock aquifers have very distinct anisotropy and in Southern Africa, North – South striking structures are usually tensional, carrying most of the water into a mine. East-West structures tend to be compressional because of the plate tectonic regime and can be barriers to groundwater flow.
Permeability is proportional to aperture cubed, therefore, the width, vertical and lateral extent of the apertures in the water bearing geological structures are important to know for use in inflow calculations.
Accurate logging of core and underground or in-pit structural mapping is essential to understand the direction and risks of inflows to mine workings in both the short term and for life of mine. This paper describes the occurrence of fracture-controlled flow in mines, methods of mapping, logging and use in mine inflow simulations.
Keywords: Structural mapping, inflows, dewatering, faults, boundaries, compartments
2022 – The use of groundwater monitoring and underground pressure release tests to benefit block caving.
Abstract
Groundwater affects all aspects of block cave and sublevel caving. The use of gravity to drive ore into the ore passes means that all liquids including mud and water, gravitate to the drawpoints and lowest points on the mine. Mine dewatering design requires knowledge of inflows, groundwater volumes and gradients.
Accurate groundwater level and pressure monitoring enables the plotting of groundwater gradients around a block cave which then allows understanding of groundwater flow directions. Once the flow directions are known they can be diverted away from the active caving areas to reduce risk of inflows, reduce mud rushes and increase production. Techniques for measuring head and the use of pressure release tests (PRTs) to obtain hydraulic parameters are given and case studies are discussed.
Keywords: dewatering, pressure release tests, groundwater, inflows, mud rush, depressurisation, flood
2021 – The use of mineral exploration drilling to kickstart hydrogeology data collection for pre-feasibility mining studies and beyond.
Abstract
Valuable groundwater information becomes available as soon as drilling starts, particularly during early mineral exploration campaigns. Often the information is not collected as the value does not become evident until the exploration sites become a mine. This paper describes what information can be collected very inexpensively during exploration drilling and how drill holes can be used to create an early monitoring network for the collection of water levels across the site.
Examples of logging sheets, daily drill records and construction designs for monitoring boreholes are provided.
During drilling and logging of exploration coreholes the emphasis is all on characterising the orebody. Drilling methods include rotary, air percussion and core drilling. All encounter water and, with very little effort, the information on water intersections, drilling fluid circulation losses, basic water chemistry and rest water levels can be collected by the drilling contractor and the site geologist, under direction from the project managers. If the basic information is captured, then this significantly reduces the cost of the initial hydrogeological study for the pre-feasibility reports. Some of the holes can be equipped for use as water level monitoring boreholes or preserved for use at a later stage. Old core holes that are not sealed can create conduits for underground inflows when the mine is developed.
Decision criteria are provided for the use of the hole after drilling to optimise information from all drillholes and reduce risk when mining commences.
Keywords: Water, Mine Design, Inflow, Flood, Precipitation, PFS
2021 – The Use of Accurate Pore Pressure Monitoring for Risk Reduction in Tailings Dams.
Abstract
Simply monitoring movement of the tailings dam wall does not address the cause of tailings dam failures and will therefore never be an effective method to reduce or prevent failures. Monitoring the causes of failures is more effective. The main cause of tailings dam failure is slope instability, which is caused by too much water in the wrong place.
Accurate pore pressure monitoring of the pressure (weight) of water in the tailings storage facility (TSF) slopes and plotting of flow lines beneath and upstream of the TSF can guide and enable early intervention to prevent or delay failure. Remote monitoring linked to artificial intelligence and robotics to turn on pumps and open drains to address and remove the cause of failure can help reduce risk. Installation of multiple point piezometers in an accurate pattern allows the plotting of equipotentials and flow lines in three dimensions. Each TSF is unique and requires its own monitoring design, which should be tailored to match the age, structure, and specific causes of risk. Once understood, the monitoring system can be coupled to a reporting system to significantly reduce the risk of failure at both legacy and active sites.
Keywords: Piezometers · TSF · Robotics · Artificial intelligence · Equipotentials · Satellite tracking
2021 – Advances in tailings monitoring, a hydrogeologists perspective.
Abstract
Trends in Tailings Storage Facilities (TSF) monitoring are changing. Standard techniques include the use of prisms and radar, Lidar, satellite, and photogrammetry. All measure the movement of the TSF however, although these methods measure movement of the TSF, they do not address the cause of movement or failure of the TSF. 2021 has seen a shift in monitoring techniques with more thought applied to addressing and controlling causes of movement.
This supports more accurate risk management and enables quantitative mitigation of risk.
From a hydrogeological perspective, the use of pore pressure monitoring has definite value for understanding hydraulic pressures upstream, downstream and below a TSF. Targets for maximum pressures or maximum acceptable rates of change in pressures can be set and used to prevent failure. Accurate monitoring in real time coupled with intervention techniques such as pumping, drainage of footwalls or drainage of ponds can manage and increase the stability of sectors of the TSF. Addition of a regular in situ geophysical survey, such as the G.RE.T.A. system enables blanket coverage of a slope or embankment. The theory and some examples of monitoring networks coupled with real time monitoring, visualisation and control dashboards illustrate the paper.
2021 – A historical perspective of diamond mine dewatering design and guidelines for modern diamond mine.
Abstract
Diamond mining in hard rock has been practiced since the late 1800’s. Mine dewatering design has been an important consideration in the mining of kimberlites. The mining of kimberlites tends to follow a specific methodology. Diamonds are mined open pit to about 350m below ground level, then, when the cost of driving tonnes up roadways to the plant becomes uneconomic a shaft is sunk and methods such as blast hole open stoping, sub level caving, block caving or a combination is used.
Each mining method has a specific effect on the groundwater surrounding the pipe. The hydrogeology of typical kimberlite mines is detailed and the methods of keeping water away from the mine workings are described. Early underground mines used water tunnels, connected by water passes to divert rainwater and near surface groundwater from the mine workings. Shafts with multi-stage pumping levels were used to pump water from the deepest sections of the mine. At Finsch mine a decline, 650m deep water ring-tunnel (combined with a conveyor belt level) and deep pumping boreholes were used to dry the initial block cave to 720m below surface.
Using experience gained on the deep mines, modern dewatering techniques have been developed and managed using monitoring networks to enable accurate management of underground water including the reduction in mud rush risk.
This paper summarises the techniques used to manage pit and underground water, its links with mud rush occurrence and lessons learnt over the last 120 years. It concludes with a good practice dewatering design and water management strategy for modern mines.
Keywords: Monitoring, Groundwater, Feasibility Studies, Environment, Optimisation.
2020 – The Zone of Relaxation: Advanced Mine Dewatering Strategy for Finsch Mine, South Africa.
Abstract
2020 – WIN WIN: A women-driven initiative for the cleanup of mine dump residue.
Abstract
South Africa’s heritage of over 150 years of gold mining in the Witwatersrand area is continuous exposure of sulphide rich soils and mine dump residue to rainwater. Rainwater increases the acidity in the soils and ground water contributing to the acid mine drainage problem prevalent across 120km of semi-urbanised land. Many of the easily accessible dumps have been removed by mechanised hydro-mining leaving behind thick skins of toxic sediments and contaminated soils.
Collection and clean-up of the residual soils requires manual labour. Polluted land has a reduced value despite being very close to fast growing nodes of urbanisation. This short paper describes how the South Africa Government’s Working for Water Programme (WfW) can be adapted to create a WIN WIN programme where training and employment can be used to remove polluted sediments and pay for itself by selling the valuable metals and increasing the
value of the land. The paper concludes by listing the advantages of the WfW clean up to social development, water protection and economic development of the Witwatersrand. Implementation in other polluted areas is a possible add-on.
Keywords: ICARD | IMWA | MWD 2018, WIN-WIN, water protection, ground water protection, land values and social upliftment
2020 – Tailings dam risk reduction using accurate pore pressure monitoring.
Abstract
The January 2019 Brumadinho tailings dam failure in Brazil which killed over 250 people has created worldwide focus on what can be done to reduce tailings dam failures. South Africa has had its own tailings dam failures; notably the Merriespruit failure in Virginia in 1994, where 17 people were killed and many houses destroyed.
Modern techniques for tailings dam monitoring emphasise the measurement of movement of the slopes using radar, LIDAR and prisms; however these techniques only measure the reaction of slopes to instability factors and do not address the causes or assist with reducing risk. The biggest preventable cause of slope failure is too much water, either in the pond or from the weight (measured as pressure) of water in the tailings slope faces. Pore pressure monitoring is an accurate method to measure the weight of water in a slope and enables early intervention to delay or prevent failure. Pore pressure monitoring methodology and techniques are described with recommendations on a standardised but bespoke monitoring network for each high risk tailings dam. The mechanisms of failure are discussed and the best practice for monitoring required to predict failure is presented. Open pit slope stability techniques can be used to manage dam wall stability. The success of accurate monitoring design depends on the location, construction and management strategy for a tailings storage facility (TSF). Different monitoring networks are required depending on the type of dam and the impact of the catchment on its water balance. Pore pressure monitoring is proposed as an effective method to predict instability as it addresses the cause of the potential failure. Big Data techniques are now available to manage multi-point monitoring sites and telemetry can transmit real-time information which can then be depicted in a dashboard to present knowledge and identify risk. This can be used to prevent failures and act as early warning systems for those that cannot be prevented. An example of a monitoring network, installation and reporting is given including recommendations for implementation and transmission of real-time information linked to action.
2018 – The Anatomy And Circulation Of Mine Water In Carbonatite Mines, Specifically Diamond Mines.
Abstract
Ground water occurrence and movement around and in Carbonatite mines, specifically diamond pipes, are dominated by three types of structures; first is the weak zone which allowed the carbonatite to be emplaced; second are the structures that opened when the emplacement occurred and third are the relaxation structures created by mining the ore body and country rock. The latter is described as a Zone of Relaxation (ZOR).
They are all significant because they control the mechanism allowing the country rock water to enter the mine workings and are important components of the conceptual hydrogeological model. Knowledge and measurement of the three structural domains enable more accurate interception and control of the dewatering over life of mine. Generic domains are discussed, and examples are given from Finsch diamond mine, South Africa.
Keywords: Dewatering, inflows, kimberlite, Zone of Relaxation, ZOR, conceptual modelling, fracture flow
2017 – Alternate solutions for acid mine drainage – making profit from waste.
Abstract
Acid mine drainage (AMD) has been documented along the Witwatersrand since 1903. Acidic mine-water is created when water and oxygen come into contact with the sulphide mineral pyrite (FeS2), which occurs in underground workings, outcrop, and all mine waste residue dumps. When exposed to oxygen in the vadose zone, mine workings and shafts where water levels fluctuate are the main sources of acidic water.
The AMD contains high concentrations of metals, sulphates, and salts.
The current government initiative is to pump out the AMD and add lime. The Department of Water and Sanitation (DWS) has spent over R3 billion on equipping three shafts to raise 166 Ml of water per day from the West, Central, and Eastern basins. This water, which has a pH of around 3, and is then treated by the addition of expensive and scarce lime to a pH of 8 or 9. The water is still not fit for use (drinking or agriculture) but is pumped directly into the nearest watercourse. The change in pH enables some metals to precipitate out, and a super-toxic sludge is dumped at the headwaters of the streams. The released water has extremely high sulphate levels (>2000mg/l) (Department of Water Affairs, 2016).
The government plans a second phase of treatment of the pumped water. Four conventional treatment methods are being considered and the Water Research Commission (WRC) is investigating other less well-known options. All are power-hungry and expensive.
Continuous pumping is cited as a solution to the Gauteng region’s AMD problem, but this exposes more pyrite to oxygen and water, thus increasing the amount of polluted water.
2017 – The business case for accurate mine water management.
Abstract
During the recession the mining industry has reduced costs wherever possible. The easy cost cutting has been done. Innovation in faster, better and cheaper ore extraction has led the way with emphasis on reductions in maintenance (just-in-time) and targeted management of input costs. One area which has been neglected is the reduction of water costs. Reducing the cost of water to business has the added advantage of reducing the costs of managing environmental impacts.
Water affects mining as input and output costs. Water is used in all aspects of production and processing. Ground water, in particular, is often misunderstood and intercepted at the last possible moment resulting in increased costs for pumping and treatment which is often not necessary if the water is intercepted prior to coming into contact with the ore body and pollutants such as diesel.
2009 – Comparison of Designs for the Dewatering of Coal, Gold and Diamond Mines in Southern Africa.
Abstract
Although the fundamental premises underlying the choice of mine dewatering design are the same for all mines, experience on Southern Africa Mines has shown that there are differences between the designs adopted by gold, coal and diamond mines. These are primarily in the areas of approach, methodology, design and application.
The major contributing factor to the choice of dewatering design adopted is the initial perceived life-of-mine. Two mines of the same age can have very different designs depending on the original planned life of mine. Case histories are given with details of the dewatering designs.
2007 – Block cave dewatering: A case history from Finsch diamond mine, Northern Cape.
Abstract
Finsch Diamond Mine was opened in 1966, the pipe at surface was elliptical with an area of 17.9ha, and is known to extend beyond 1200m below surface. Mining by means of open pit, until a final economical depth of 423m was reached in 1990. Blasthole open stopping was adopted until 2004 when Block 4, the first planned block cave, came into production. Finsch Geology includes dolomite below 29 level (290m depth).
Groundwater flows through major structures. The early installation of ring tunnels from 1979 to 1984 advance dewatered the mine by passive drainage to about 630m depth. Below 630m active dewatering has been achieved by the installing of 7 pumping boreholes. A piezometer network shows that the active dewatering is able to maintain a piezometer level below the 65 level and therefore 20m below the block cave.
2003 – Hydrogeology of Venetia diamond mine, South Africa.
Abstract
Venetia Mine is located in the northern part of the Limpopo Province . The mean annual rainfall for the area is 344mm and the mean annual evaporation is in the order of 2650mm/annum. Geologically, Venetia Mine is situated in the Central Zone of the Limpopo Belt where a large variety of rock types are developed. These include quartzites, dolomitic marbles, magnetite rich quartzites, amphibolite’s, gneisses and schist’s.
During the hydrogeological investigation a number of boreholes were drilled and were subjected to numerous conventional and unconventional aquifer tests. The country rock of the mine is hydraulically tight but has a large storage capacity for groundwater. Faults and fractures within the country rock enhance the hydraulic conductivity in places and serve as drainage lines into the open pit.
The kimberlite may be divided into two significant horizontal hydrogeological units, the so-called “overshotzone” created by drilling and blasting and the undisturbed kimberlite . The “overshot zone” has a high density of artificial fractures and is between 2m and 5m thick.
Test pumping of !he in-situ kimberlite of the Venetia Diamond Mine has revealed unusually high hydraulic values. Post closure, evaporation might exceed the inflow of groundwater into the pit. It will, therefore, either be dry except for runoff from precipitation or develop into a brine lake where accumulation of salts will take place in the pit. The drawdown of the groundwater table will continue indefinitely because evaporation exceeds recharge. A pit lake model is planned to simulate post closure conditions.
2002 – Back to basics – the quest for good hydrogeological data.
Abstract
The development of complex ground water modelling codes and the increased capability and computer based models means that the collection of accurate and pertinent data has become even more important. The development of modern hydrogeology is described. Checklists and pit falls in field investigations are given with specific emphasis on the measurement of hydraulic heads underground and monitoring preparation for test pumping.
The use of point piezometers, as against the rising tendency to install open hole monitoring boreholes, is emphasised.
2000 – The use of thermal imagery in groundwater studies.
Abstract
Airborne thermal imagery and its use in ground water location is not a new technique, however recent developments in Global Positioning Satellite (GPS) technology means that the ground water signatures on the image can be accurately pin pointed in the field. The low cost and simple technology makes it very at- tractive to development programs.
Recent surveys in Southern Africa have been used to determine the position of dolomite aquifers, polluted ground water, seepage from slimes dams, geological structures, abandoned mines, underground fires and kimberlites. Examples of different applications are given in the text and as a projected presentation.
1994 – Impact of groundwater on mining at Finsch Diamond Mine.
Abstract
The paper evaluates the relationship between mining and ground water at De Beers Consolidated Mines Finsch Mine situated in a semi-arid region of the north western Cape in the Republic of South Africa. A detailed groundwater investigation was commissioned in May 1992 aimed at evaluating the groundwater regime and to define the possible scale of groundwater occurrence with the downward extension of the mine.
The assimilation of data available prior to the investigation coupled with remote sensing and field techniques, led to an understanding of the groundwater flow and compartmentalisation.
Preliminary results from the investigation indicated that the mine is actively recharged from rainfall events in both the immediate vicinity of the mine and distant karst systems. This led to the development of a recharge simulation model to predict the ground water levels response to rainfall and to determine the water balance for the aquifer for the life of mine. The understanding derived from the study was of crucial importance in improving the effective management of groundwater and its recognition as an exploitable resource. This led to a number of cost saving strategies.
1994 – Mine drainage control and environment protection by using grouting technology and the hydrogeological approach.
Abstract
Any dewatering project needs to include a thorough understanding of the ground water regime affecting the mine. This means understanding the origin, movement, volume and hydrogeology of the country rock and the ore body.
1993 – A phased approach to mine dewatering.
Abstract
The construction of an excavation often means penetrating the local or regional water table. This causes inflows, which if the country rock is significantly permeable can become at best a nuisance to operations and at worst a hazard. Dry working conditions are preferable as they reduce wear and tear on machinery, reduce earth moving costs and often improve slope stability and therefore safety.
Options available to mine management are dewatering, diversion, sealing or a combination of methods. To achieve the most effective, least cost method it is essential that the origin of the ground water is determined. The success of a dewatering exercise is directly linked to an understanding of the ground water regime. Mines cannot afford to use “blanket methods” when dealing with ground water. It is essential to target the actual inflows and not divert or seal off water indiscriminately.
The potential impact of groundwater inflow to a mine can often be assessed at the prefeasibility stage. A hydrogeological investigation is best tackled in three phases. The first phase is a desk study and borehole census and can be initiated by the mine or quarry developers. The main objective is to determine water levels and regional hydrogeology. It is very important that the Phase one hydrogeological investigation is started at the same time as the geological investigation. All exploration drilling records should include comment on where water was encountered and in what volume.
The objective of Phase two is to indicate at a first level of confidence the probable impact of mining on the groundwater and vice versa. The level of confidence is determined by the quality of data collected in Phase one. At the end of Phase one management will be able to assess if water is going to prove a hazard to mining or not. If it is going to be a hazard then Phase three will be activated. The objective of Phase three is to plan how to reduce or remove the hazard and either handle or divert the probable inflows.
Phase three can be accomplished through trial dewatering, computer modelling or through the application of practical experience. The level of sophistication at Phase three is determined by the potential costs and risks involved.
1993 – Evaluation of a fractured rock aquifer.
Abstract
Text book methods of planning and executing an aquifer evaluation programme usually emphasise primary aquifers. The secondary or fractured rock aquifer requires a more rigorous exploration programme with emphasis on the following steps:
1 Aerial photograph, satellite imagery and structural interpretation.
2. Target geophysics and resource modelling.
3. Drilling and test pumping analysis.
4. Water balance assessment and aquifer stress analysis.
5. Aquifer modelling and management.
Each step has to evaluate two types of aquifer response; the response of the ground water flowing within the fractures and the response of the ground water feeding the fractures. The first response is governed by the size, distribution and orientation of the fractures. The second response is governed by the storage characteristics of the inter fracture matrix and the weathered zones in hydraulic connection with the aquifer. The neglect of one or the other during the analysis of test pumping data leads to an incorrect evaluation of the aquifer. Different methodologies are used for large regional scale as compared to village scale ground water exploration and aquifer assessment projects.
1988 – The prediction of minewater inflows.
Abstract
Uncertainties in the forecasting of the volume of groundwater likely to enter underground workings present difficulties for mine management in planning and costing the water-related activities of mining. This paper describes a technique that was developed to assess future inflows into a gold mine in the Orange Free State. The approach employed was based on the interactive operation of two separate computer models: a regional-flow model and an inflow model.
As a first stage, a regional finite-element model of groundwater flow was set up and calibrated. Predictive runs were made to establish the influence of mining on the water levels from base-line conditions. This step was necessary since observations of the regional water levels were sparse. The predicted water levels were transferred to the inflow model, and the future flowrates were calculated.
Both models were calibrated by trial and error until a satisfactory match was obtained between historical records and the values predicted by modelling. In this way, an improved monitoring system to record regional water levels and pressure heads within a mine was established. By the use of information, the initial model predictions can be refined as mining progresses. The models used are based on a non-linear relationship between the area mined and the inflows. A phased behaviour in the rates of inflow increase was noted.
In conclusion, the modelling approach can provide mine management with guidelines for dewatering requirements. The confidence levels depend upon the records that have been collected during the mine’s history.
1987 – Calculation of Mine Water Inflow using Interactively a Groundwater Model and an Inflow Model.
Abstract
The uncertainty of the we-evaluation of potential groundwater inflow rates in underground mines results in difficulty in planning and costing the water related activities of the mines. This paper presents a procedure for making a rational assessment of the potential inflows.
The method is based on an interactive operation of two computer models: an inflow model and a ground water finite element model.
Both are first calibrated using existing information obtained from aquifer monitoring. In a second phase, the models predict the potential inflows as well as the impact of mine dewatering on the piezometric surface. Both the models used are based on a non linear relationship between tonnage mined and inflows. A phased behaviour in the rates of inflow increase is noted.
The interactive mode of operation of the models results in confidence in the prediction because the models output (calculated inflow rates and piezometric levels) during the calibration phase are checked against the historical data. It is concluded that the method can provide mine management with guidelines for dewatering requirements under the condition that reliable data on the history of piezometric levels be available.
1987 – The optimisation of conjunctive use for water supply: A case study.
Abstract
A local mine complex in the planning phase requires a water supply for both potable and plant process use. A number of regional supply sources were investigated and found to be excessively costly. It was therefore decided to investigate the supply of water to the mine complex from local surface and groundwater sources.
It was considered at the outset that a conjunctive use approach using both surface and groundwater would be appropriate. First the quantity of surface and groundwater available to the mine within physical, legal and economic constraints had to be verified. Cost-risk matrices were then developed to compare the options available to the mine for several water demand scenarios from a number of combinations of dams and wellfields. The final recommendation was the combined use of a gravity dam and three boreholes with the boreholes used to supplement the dam during periods of low river flow.
1984 – The Influence of underground coal mining on Ground water.
Abstract
Due to a combination of geologic and economic factors, bord and pillar mining was, until comparatively recently, employed almost exclusively in South African coalfields. Even today, at shallow depths and moderate seam thickness, it is difficult to improve on for productivity, cost effectiveness and percentage extraction. An advantage of this method, in which coal pillars are left unmined to support the overlying strata, is that the ground surface and sub-surface strata, and hence the ground water regime, remain largely undisturbed.
However, in 1964 the scarcity of coking coal and the rapid decrease in percentage extraction with increasing depth and seam thickness using bord and pillar mining methods prompted trials with caving or total extraction mining methods. Application of these methods gained additional impetus following publication of the Petrick Commission Report in 1975 which recommended a substantial increase in the controlled price of coal and which consequently resulted in an improvement in the economic viability of total extraction mining methods. ‘These methods, notably longwall, pillar extraction and rib pillar extraction, allow the overlying strata to collapse into the excavation formed by the removal of the coal and thus result in considerable disturbance of the overlying strata. This has a disruptive effect on the surface run off and the sub-surface ground water regime.
The object of this paper therefore is to examine the mechanism and consequences of disturbance of the ground water regime by total extraction mining methods.