The study describes the application complimentary geohydrologic tools to investigate the geohydrological properties of an alluvial channel aquifer and its interaction with the river surface water resources. Primary field investigations were designed to determine the geologic, hydraulic, hydrogeochemical and solute transport properties of the alluvial channel aquifer as an important component of the groundwaterâsurface water (GWâSW) interaction system. The secondary investigations were then aimed at assessing groundwater discharge and recharge mechanisms of the alluvial channel aquifer at a local scale (< 1000 m). A water balance model was developed for the groundwaterâsurface system as a tertiary level of investigation. Geological characterisation results show the spatial variation in the physical properties of unconsolidated aquifer materials between boreholes and at different depth. The drawdown derivative diagnostic analysis shows that the alluvial channel aquifer system response during pumping can be described by the following major groundwater flow characteristics; Typical Theis response; transition period from initial Theis response to radial acting flow (RAF); radial acting flow in the gravelâsand layer and river single impermeable boundary effects. Detailed studies of the hydrogeochemical processes in the alluvial aquifer system have shown that dissolution of silicate weathering, dolomite and calcite minerals, and ion exchanges are the dominant hydrogeochemical processes that controls groundwater quality. Quantitative and qualitative investigations indicate that the alluvial channel aquifer is being recharged through preferential infiltration recharge as facilitated by cavities and holes created by the burrowing animals and dense tree rooting system. Tracer tests under natural gradient were successfully conducted in an alluvial channel aquifer, thus providing some advice on how to conduct tracer breakthrough tests under natural gradients in a typical alluvial channel aquifer. The findings of the study also highlights the value of developing a water balance model as a preliminary requirement before detailed GWâSW interaction investigations can be conducted. Based on the theoretical conceptualizations and field evidence it is suggested that studies be conducted to determine if alluvial channel aquifers can be further classified based on the nature of the hosting river channel. The classification would split the alluvial channel aquifer into alluvial cover and fracturedâbedrock, or a combination of the two. The applications of the PhD thesis findings are not only limited to the case study site, but have important implications for GWâSW interaction studies, groundwater resource development and protection in areas where groundwater occurs in alluvial channel deposits.

Over the last 15 years the Windows Interpretation System for the Hydrogeologist (WISH) was developed by the author of this thesis. The program is used by numerous mines and consultants all over South Africa and abroad. WISH does not discriminate between mining types as it is just as capable of handling all water issues in the gold mines, platinum mines, iron mines or as the title of this thesis implies coal mines. Many other water related software packages are available. Most of them are developed for a single purpose. (Borehole logs, pumping tests, chemistry graphs or mapping) WISH is different because it can do it all. WISH was developed with the Hydrogeologist in mind. When a graph is requested WISH will create one first and subsequently allow the user to modify the graph. The volume calculations for opencast and underground mines are a breeze and no other existing software can do this with so much ease. Many collieries in South Africa are using WISH, not only for the chemistry and time data capabilities, but also for the management of large volumes of water. Many collieries trust WISH to calculate water capacity and water volumes in the mines. Decisions are taken to build 200 million rand water treatment plants. This thesis discusses the development and existence of WISH. A comparison with all other (ground) water related software available worldwide followed by a more in detail description of WISH and a quick starter guide on how to create a WISH document. A chapter is dedicated to recharge and decant followed by a discussion on how to use WISH in a real life project.

A new opencast coal mining operation is proposed in the Belfast region in Mpumalanga, South Africa. This proposed operation is the study site that was investigated in this thesis. The Belfast opencast operation is expected to be operational for 29 years and coal from mainly the number 2 and 3 seams will be mined. The inflow rate of the groundwater was determined by using both analytical and numerical groundwater methods. The rate at which groundwater flows into the mine voids are important to estimate before mining commence since this will determine at what rate groundwater needs to be pumped from the mining pits to ensure dry and safe working conditions. In order to obtain site specific data for the study area, several field investigations have been conducted. These investigations include a geophysical survey, drilling of monitoring boreholes and pump testing of the monitoring boreholes. These investigations are done to obtain a better overview of the aquifer conditions in the study area. For the study area a numerical groundwater flow model was constructed and the groundwater inflow was determined by making use of a water budget function. The analytical approach to determining the inflow included four different methods. A sensitivity analysis was done on the recharge with the numerical and analytical methods. The results from the numerical and analytical approaches were compared to determine whether the analytical approach is in fact a good way of obtaining values that relates with the numerically obtained results. If there is a good correspondence between the analytical and numerical results, the analytical approach can be regarded as a save and representative way to obtain groundwater related values. Especially during the early stages of mine planning analytical methods would be supportive to quickly determine mine related issues as this will assist in decision making and related cost estimates. From the results obtained in this thesis it can be concluded that the analytical approaches used during this study, although giving close to numerical answers, cannot be used in an effective manner in determining groundwater inflows during the early planning of mining. The fact that the analytical approaches did not reveal representative values for the groundwater inflows and also do not correlate with the numerical model results, does not mean that this will be the case at another site with different geohydrological characteristics. It is important to note that assumptions are always made in analytical methods. It is suggested that further research be conducted in relation with analytical and numerical modelling of opencast mines. Research should be performed at several mines to determine whether the relation between the numerical and analytical approaches display similar trends than was found during this study. These mines should preferably be on similar geological areas to compare with each other. The only way to determine whether the analytical methods can in fact be used to get a representative result is by repetition on several mining sites and also comparing these values with the numerical model results and also the actual inflow rates from the mine once mining has started.

A key challenge for chromium related activities, such as in ferrochromium industries, is the disposal of waste containing chromium slag or dust with hexavalent chromium (Cr(VI)). Various investigations have shown that hexavalent chromium is a serious concern to both environment and human health because of its mobility and carcinogenicity (Fendorf et al.; 2003). This study evaluates the impact of chromium on groundwater in the unsaturated and saturated zone by human related activities. A South African ferrochromium industry sector based in the Mpumalanga Province, (Middelburg) was selected as a case study to assess a waste dump of ferrochromium slag. The challenges regarding the dumping of slag are the oxidation of trivalent chromium (Cr(III)) to hexavalent chromium, as well as fine dust from the open arc furnaces which contain hexavalent chromium. At the case study site, the historic dump site (HDS), which is not lined, was previously used to dump various waste materials (since 1964), including but not limited to: ï· Ferrochromium slag ï· Phenols ï· Fine dust from open arc furnaces (with hexavalent chromium) ï· Filter cake (with hexavalent chromium) Literature studies indicate that trivalent chromium can be oxidised to hexavalent chromium Cr(VI) through presence of moisture, dissolved oxygen and manganese dioxide (MnO4) (EPA, 1994). The literature also indicates that concentration of hexavalent chromium Cr(VI) greater than 1 mg/l imparts a yellow colour (US EPA (1994) which was used as a visual indicator during field assessments at the HDS. The presence of hexavalent chromium was observed at the toe of the dumps and in low lying areas surrounding the dumps with elevated moisture contents. The presence of hexavalent chromium was also confirmed by monitoring results for both surface and groundwater. The mitigation that has taken place on site, involved the removal of hazardous waste such as fine dust and filter cake with hexavalent chromium from the HDS, and dumping it at a hazardous waste site (Holfontein). Other on-going mitigation at the dump is the usage of ferrous sulphate at the capturing point (infiltration gallery) to reduce hexavalent chromium to trivalent chromium through oxidation-reduction (redox) reaction process. This study has indicated that although some remedial approaches have been performed, the contamination still exists at the site. The findings of the study assessment have indicated the following: ï· Boreholes near the process plant indicated contamination by both trivalent chromium and hexavalent chromium. ï· Dam 4A and 4B have the highest concentration of hexavalent chromium as well as other constituents, such as sulphate (SO4). ï· Boreholes down-gradient of the HDS indicated pollution by hexavalent chromium, sulphate (SO4) and other parameters. ï· The western boreholes showed a trend of increasing pollution by sulphate (SO4), though not by trivalent or hexavalent chromium. Background boreholes did not show any pollution. ï· Contamination to the unsaturated zone is high but also differed when compared to contamination in saturated zones. ï· Contamination by hexavalent chromium is caused mainly by the fluctuating water table during water spraying (cooling) of hot slag, and due to precipitation in the rainy season.

The purpose of the study is to investigate the influence of flooding on underground coal mines. Two case studies were investigated the shallow underground Klibarchan coal mine and the deep underground Usutu mine. Kilbarchan colliery is located 10 km south of Newcastle in KwaZulu/Natal. It comprises two underground sections, called Roy Point and Kilbarchan. Usutu colliery is situated just 8 km outside the town of Ermelo in Mpumalanga, close to Camden power station on the N2 road to Piet Retief. The geology of both studies lies within the Karoo Group, Ecca subgroup in the Vryheid formation. Higher precipitation at Usutu and Kilbarchan occurs in the summer months, while Kilbarchan has a higher annual rainfall of 864 mm/a compared to Usutuâs 705 mm/a. The water levels at both mines yielded interesting findings. Usutu mine is compartmentalized with walls in the underground. These walls are so strong that they function as âlow pressureâ seals resulting in compartmentalized underground, withstanding the huge pressures created by the recharged groundwater. This causes water levels to differ in the underground. Water levels at Kilbarchan mine vary in depth, but when plotted in metres above mean sea level (mamsl) they plot in a straight line. Regional recharge at Usutu was calculated as 5.7 % and 11.3 % at Kilbarchan. Recharge is influenced by what type of mining activity was practised in that specific area. It was concluded that recharge on opencast is between 15 to 20%, the stooped area between 10-15% and in an underground shallow mine it could be as high as 10%. Mining activity ceased in 1992 at Kilbarchan. Pumping is a common practice at flooded underground mines, because the mine needs to be filled with water on an ongoing basis. This prevents sulphate generation and the water quality from deteriorating. Pumping at Usutu is well managed and flushing started to occur in the underground with the electric conductivity improving over time. Pumping at Kilbarchan is poorly managed and over pumped. The electric conductivity over time, is not improving indicating that oxygen infiltrates the system when too much pumping occurs. Bord-and-pillar mining followed by stooping has been the main mining method. At Usutu mining activity ceased in the late 1980 and then the mine was flooded. It is finally there is concluded that an underground should be flooded as quickly as possible and then managed well. Shallow underground mines have a higher potential of contamination, because of a shorter residence time. The depth of mining, topography, mining methods, water levels, exposure to oxygen, rainfall, recharge, residence time and pumping have an influence on the effects of a flooded coal mine.

South Africa has several coal mines of which promised economic wealth since the 1700, however the exploitation of this commodity has a negative effect to the environment. Mining operations are a source of Acid Mine Drainage (AMD) in South Africa therefore salt loading and acidic conditions are of concern. Although lab methods such as Acid-Base Accounting (ABA) are used to predict the impact and effects of AMD, it is still difficult to predict its rate. The importance of laboratory analysis is to give the best and worst case scenario of the area, provided that the samples are representative of the area investigated. This thesis is conducted to note the difference between South African and Australian Laboratory methods in determining the potential and existing acidity of the samples. Furthermore, AMD is predicted using ABA methods for the Middelburg area. South Africa uses similar ABA laboratory guidelines as USA and Europe while Australia uses its own guidelines that are modified from time to time. After the comparisons of the methods were evaluated, the Australiaâs versus the South African results showed a very good correlation. However the Ca percentage from the ICP results had a lower correlation compared to other cations in the Actual Acidity Method. The KCl and NaOH used in the Australian Actual Acidity Method either displays the Ca as double or half of the South African ICP results. However, both countriesâ Actual and Potential Acidity Methods are comparable. The Australiaâs Neutralising Potential Method is derived from lime analysis disciples and can be an overestimate of the Neutralising Capacity. Whether the methods and results of Neutralising Capacity can be compared or not, is inconclusive. Other ABA tests have to be done on the same samples to verify if personal, analytical or instrumental error was significant. To achieve another aim of this thesis, The IGS was approached by Middelburg mine services to update the 2006 groundwater model at Goedehoop, Hartebeesfontein, Bankfontein and Klipfontein Collieries. At a later stage, Acid-Base Accounting (ABA) methods were requested for AMD prediction. The aim of the project was to do groundwater assessment of the collieries and predict future impacts of AMD. The locality of the investigated area is in the Middelburg, which falls in the central Highveld of the Mpumalanga province in South Africa. Open-cast coal mining is in operation at Klipfontein, Hartebeesfontein and Goedehoop. Klipfontein is along south of the Vaalbankspruit while Hartebeesfontein and Goedehoop spreads north of the Spookspruit. The area is in the Karoo Supergroup which underlines two thirds of the Republic of South Africa with typical rocks like sandstone, mudstone and shale. About 4.7 % of the representative samples from the Middelburg Collieries showed a Net Neutralizing Potential in the Static test method whereas Kinetic tests results proved that only a handful of the samples had a low salt load and a limited buffering capacity. In conclusion, the representative samples showed the investigated Middelburg Collieries had high-medium risk of acid-generation upon oxidation. With the prediction of AMD done, control measures can be put in place. The primary objective of AMD treatment is to remove metals (i.e. sulphides, hydroxides and carbonates) and raise the pH to alkalinity. Passive or Active treatments could be used to remedy the area. The deteriorated water quality caused by the coal mining area could be remediated and released into the Upper Olifants river catchment.

None

This thesis aims at geohydrologically assess arsenic in the Jagersfontein area and hence proposing remediation option. The field procedure carried out involved hydrocensus and sampling where samples were collected and analysed for micro and macro parameters with emphasis on arsenic. Isotopic (18O, D (deuterium) and Tritium 3H) analysis was also carried out to characterise the water in terms of its origin, fate and age. A total of 20 boreholes were sampled. Historical data from Bloemwater was also incorporated in the study. According to the chemical analysis, the most abundant cation is magnesium followed by calcium, and the most abundant anion is sulphate. Three different water types were classified; sodium/potassium sulphate, magnesium sulphate and calcium/magnesium bicarbonate. Hence they are from different sources. Sample collected from the mineshaft showed highest arsenic concentration which is higher than the South African National Standards (SANS 241, 2006) guideline for acceptable arsenic concentration in drinking water while all other individual boreholes in the main town of Jagersfontein showed low arsenic concentration (<0.006 mg/l); hence concluding that arsenic contamination comes from the mine. Mine water that has been treated in package plant (JFinal) still shows high arsenic concentration. Water from Kalkfontein dam is being treated in a bigger treatment plant (went operational in July 2012) and mixed with treated mine water. This reduces the arsenic concentration of water to an acceptable level before it is finally supplied to the community. Spearmanâs correlation coefficient calculated show a weak correlation between arsenic and other chemical parameters and so it is concluded that arsenic and these elements are not of same source implying the source of arsenic is not geogenic. Isotopic analysis shows the water samples plot very close to the global meteoric water line (GMWL) implying the groundwater is meteoric and is derived from the atmosphere. Clustering of the samples around the GMWL hints they might be of the same age. However one sample (surface water sample) plotted away from GMWL and it is attributed to effects of evaporation. The hardness of the water samples is generally high. To solve this problem, individual owners of boreholes add water softeners (chlorine, crystals) to soften the water. There are several techniques available for removal of arsenic from water in large conventional treatment plants. The basic principles of these technologies are based on physical-chemical processes such as oxidation, coprecipitation and adsorption on coagulated flocs, adsorption onto sorptive media, ion exchange, and membrane filtration. Most treatment options need the oxidation of As(III) to As(V) for efficient removal of arsenic. For the case of Jagersfontein, coagulation and filtration technology (FeCl3 as coagulant) will be the best option because it is very efficient in removing arsenic (V) which happens to be the dominant specie in the water. It is the cheapest technique compared to the others and it is also less sophisticated. However what is currently done in Jagersfontein to reduce the concentration of arsenic in water is dilution/mixing. Mine water treated in a package is mixed with treated water from Kalkfontein dam. Water (not arsenic contaminated) from Kalkfontein dam is treated in a bigger treatment plant which went operational in July 2012.

Australasian, European, Canadian and American geo-environmental specialists have long been involved with pit lake studies in the physical processes and dynamics as well as the geochemical aspects of these mitigation methods and events. The use of pit flooding as an environmental post-closure option has however been studied and used to a limited extent in Southern Africa and Africa to a whole, with some recorded cases mostly being by accident rather than a planned mitigation. This document is a written paper on a hydrogeochemical investigation on the feasibility of flooding an open pit platinum mine in the Bushveld Igneous Complex as a post-closure mitigation option. Various data sets and sources were compiled and processed and served as input data into a hydrogeochemical model of the expected impacts on the conceptual meromictic pit lake environment. Weathering and speciation models allowed the evaluation of the current system with thermodynamic and chemical reaction processes leading to the hydrochemical composition of the groundwater as we observe it in the field. Furthermore transient mixing simulations between groundwater, surface water and rain water was allowed to occur under various reducing and evaporative conditions. The modelled lake chemistry was then evaluated against recreational, agricultural and domestic water use standards to investigate the feasibility of the lake to be used post-closure. Final recommendations and mitigation methods were proposed with the flooding of the open pit as a post-closure option declared feasible. A final deliverable of the study was a system thinking and modelling template for hydrogeochemical modelling in various scenarios to guide other scientist through the process of modelling fluid-rock, fluid-waste and fluid-fluid interaction.

The remediation of sites contaminated by dense non-aqueous phase liquids (DNAPLs) continues to present a significant environmental challenge globally. Contributing to this challenge is the difficulty in locating source zones due to local heterogeneities in the sub-surface. Heterogeneities are significant in fracture rock environments, such as those found in South Africa, which together with the fluid properties determine the fate and transport of DNAPLs. This research is based on evaluating the effectiveness of combining traditional and novel source zone characterisation methodologies in order to delineate chlorinated hydrocarbon DNAPLs in a fractured rock environment. The research documents and evaluates the characterisation process followed in the application of various methodologies to an Investigation Site in South Africa. A site-specific conceptual site model is presented indicating the delineation of the multiple chlorinated hydrocarbon DNAPL source zones at the site. Additionally, a DNAPL source characterisation approach is proposed for application in fractured rock environments. This approach allows for the convergence of traditional approaches (such as drilling within a fixed grid) with more novel approaches (such as high resolution sampling and analysis). The pioneering use of ribbon NAPL samplers (FLUTeTM activated carbon technology membranes) in South Africa is documented in this research. In situ source zone characterisation using this technology in a fractured rock environment is shown to be successful in determining depth discrete fracture transmissivities and residual DNAPL zones that would have gone unobserved through methods such as direct observation and testing rock cores with hydrophobic dyes. The efficiency of this technology renders it ideal for future continued use in South Africa.