Abstract Knowledge of the healing properties of some groundwater sources has been passed down through the generations. A complex array of hydrogeological environments yields a rich and diverse range of chemical compositions, and cures for a variety of ailments were available from some spring waters. Many were sourced with associated religious overtones. It is likely that exposure to clean cold water alleviates the symptoms of leprosy and probable also that it relieves rheumatic pain. However, the only demonstrable medicinal properties of groundwater are its purging effects wherever MgSO 4 or Epsom salts prevailed. Clean and potable groundwater is certainly a key to human health and some of the minerals dissolved within it are essential to the human body, although many of these minerals become toxic if present in excess. The modern fashion for bottled groundwater, often perceived to be associated with health-giving and medicinal properties, for the most part, merely offer a safe form of drinking water.

Abstract The islands of Jersey, Guernsey, Alderney and Sark lie close to the Normandy coast of France. They expose a largely Precambrian crystalline basement of metamorphic and igneous rocks – Jersey and Alderney also expose some early Palaeozoic clastic sediments – and all have a thin but widespread Quaternary sedimentary cover. The three largest islands were progressively fortified by the British between the early 13th and mid-19th centuries, and by German forces during occupation in World War II, a legacy illustrated by the castles, forts and numerous German coastal fortifications that still adorn them. A German military geologist based on Jersey from mid-1941 to mid-1944, and a military geological team on Guernsey and Alderney during 1942, generated hydrogeological maps and reports that were then in advance of understanding of crystalline basement aquifers elsewhere in the British Isles. All the major documents have now been found in Germany, the USA and UK, although none survived on the islands themselves. Geological mapping and hydrogeological studies postwar under the auspices of the British Geological Survey were completed without access to German data. However, German and British data together now facilitate an appraisal of the heavily stressed aquifers on these small, hard-rock islands over an unusually long (65 year) timespan.

Abstract Competition for water resources between Palestine and Israel is an ongoing cause of tension. The Western Aquifer Basin forms a major part of the complex, largely karst, limestone system of the West Bank Mountain Aquifer. The aquifer crops out and is recharged solely in the semi-arid uplands of the West Bank and groundwater flows west beneath Israel to discharge at the Yarqon and Nahal Taninim springs near the Mediterranean coast. Annual recharge to the aquifer is not easy to quantify but lies within the range 270×10 6 to 455×10 6 m 3 a −1 , and current uncertainties do not support definition of a single value of long-term average recharge. The resource is heavily exploited and abstraction is directly controlled and apportioned between Israel and the West Bank by Israel. The key to equitable apportionment is the determination of the long-term average recharge to the basin, which also requires definition of the eastern boundary of the basin to confirm the recharge area. Calculations include empirical formulae and process-based models that are likely to constrain the best estimate provided that there is appropriate, ongoing monitoring. Improved understanding can then be fed back into the model.

Abstract Groundwater in Scotland has been, until recently, an under-rated resource given the abundance of surface water resources. In the last decade, a number of new abstractions have been developed and existing ones enhanced. Implementing groundwater abstraction licensing through the Scottish Water Environment (Controlled Activities) Regulations (2005) has accelerated the need to understand such schemes. Simulating the groundwater systems, which are generally small in area, with an immature understanding and where subsurface data are often sparse, is a challenge. This challenge is amplified when groundwater abstraction is proposed from previously unexploited gravel valley deposits in close proximity to large rivers. Examples of recent work undertaken for Scottish Water illustrate the important role that groundwater models have in testing and refining conceptual understanding as well as convincing regulators of the suitability of the groundwater abstraction.

Abstract The Dumfries Basin aquifer supports groundwater abstraction for public supply, agriculture and industry. Abstraction is concentrated in the western part of the basin, where falling groundwater levels and deteriorating water quality both reflect the effects of intense pumping. There are two bedrock units: a predominantly breccia–coarse sandstone sequence in the west, interfingering with a predominantly sandstone sequence in the NE and east. The basin is bounded by weakly permeable Lower Palaeozoic rocks, and is largely concealed by variable superficial deposits. Surface water flows onto the basin from the surrounding catchment via the Nith and the Lochar Water and their respective tributaries. Direct rainfall recharge occurs via superficial sands and gravels, especially in the north, and discharge is predominantly to the rivers in the central area rather than the sea. A picture is developing of two main aquifer types within the basin: the high-transmissivity western sector underlain by a fracture-flow system with younger water and active recharge and a high nitrate content, compared with the east where groundwater residence times are longer and the storage capacity is higher.

Abstract Celtic interest in groundwater has continued to the modern era in much of Scotland and Ireland, despite abundant good quality surface waters. Groundwater investigation in the 19th and 20th centuries was prompted by the need to remove water from mine workings in Scotland and to provide water for industry in the Midland Valley of Scotland and the Lagan Valley in the north of Ireland. Little development took place in the south of Ireland until relatively recently. Champions of groundwater investigation include the venerable Scottish geologists Ben Peach and John Horne, as well as lesser known advocates of hydrogeology such as John Jerome Hartley in Ireland. These workers were supported by numerous people directly and indirectly involved with developing the understanding of the groundwater resources of Scotland and Ireland.

Abstract Although mining is no longer a key industry in the UK, the international mining industry continues to expand. One of the principal legacies of past mining in Britain is water pollution emanating from abandoned mine voids and waste rock depositories. This has necessitated many expensive technical evaluations and remedial programmes in recent years, from which important lessons may be drawn for the still-growing mining industry overseas. Perhaps the single most important lesson is that there can never be too much information on mine hydrogeology and geochemistry available at the post-closure phase. As this phase is also the longest in the overall life cycle of any mine, it should be given appropriate consideration from the outset. The post-closure studies described in this paper and in this volume (as well as elsewhere) highlight the dearth of hydrological data that are usually available when compared with the wealth of geometric information available from mine abandonment plans. It is advocated that the collection of appropriate environmental data is built into the initial mine development plan and that monitoring commences from the green field site onwards. The uncertainties related to predictive modelling of mine water arisings are considerable, whilst those of predicting mine water quality are even greater. Numerous pointers towards robust mine water management strategies are identified, and a call for ‘defensive mine planning’ is made, in which relatively modest investments in hydrogeochemical control measures during the exploration and exploitation phases of the mine life cycle will yield dividends in the post-closure phase. With such measures in place, and enhanced monitoring data to hand, the conjunctive application of physical and geochemical evaluations will eventually provide much-needed predictive tools to inform site management decisions in the future.

Abstract The hydrogeological effects of longwall mines are vertically zoned. The heavily fractured strata immediately above the mine dewater, but they are typically overlain by a zone of low permeability that prevents shallower aquifers from draining to the mine. However, shallow bedrock aquifers experience head changes caused by fracturing during subsidence. New fracture void space takes up water, causing large head drops especially in confined aquifers. Increased fracture permeability affects heads because upper aquifers in high relief areas lose water through fractured aquitards to lower aquifers, and because the higher permeabilities lower hydraulic gradients and up-gradient heads, and increase down-gradient discharge. In addition, a secondary drawdown spreads out laterally through transmissive aquifers from the potentiometric low in the subsiding zone. After undermining, water levels may recover due to closure of fractures and to recharge flowing back into the affected area. Studies at two active longwall mines in Pennsylvanian coal measures in Illinois support the conceptual model, with variations. Unconsolidated, unconfined aquifers were not significantly affected by mining. At one site, heads in a moderately transmissive sandstone declined due to mining but recovered fully afterwards. Increased permeability led to enhanced well yields, but water quality deteriorated, probably because of oxidation and mobilization of in situ sulphides during the unconfined and recovery phases. At the other site, heads in a poorly transmissive sandstone fell rapidly during subsidence and did not recover; hydrogeological responses varied at the site scale due to variations in bedrock-drift continuity. Predictions and monitoring schemes can be guided by the general conceptual model, but must consider local hydrogeological variations. Effects in shallow aquifers not in direct contact with the mine can be simulated using readily available flow models.

Abstract This paper describes how tracer tests can be used in flooded underground mines to evaluate the hydrodynamic conditions or reliability of dams. Mine water tracer tests are conducted in order to evaluate the flow paths of seepage water, connections from the surface to the mine, and to support remediation plans for abandoned and flooded underground mines. There are only a few descriptions of successful tracer tests in the literature, and experience with mine water tracing is limited. Potential tracers are restricted due to the complicated chemical composition or low pH mine waters. A new injection and sampling method (‘LydiA’-technique) overcomes some of the problems in mine water tracing. A successful tracer test from the Harz Mountains in Germany with Lycopodium clavatum , microspheres and sodium chloride is described, and the results of 29 mine water tracer tests indicate mean flow velocities of between 0.3 and 1.7 m min −1 .

Abstract This paper draws together the information that has been obtained on mine water recovery since the large-scale closure of coal mines in the 1980s and 1990s. The data show that, following cessation of pumping, mine water recovery follows an exponential curve similar to the recovery of an aquifer following a pumping test. Several previously unpublished examples of mine water recovery data from around the UK are included in the paper and there is a detailed assessment of mine water recovery in the East Fife Coalfield in Scotland. The reasons for this type of mine water recovery are discussed and examples are given of the use of the data for both the interpretation and modelling of mine water recovery. In coal mining areas where no water-level recovery data are available, methods for the prediction of mine water inflow and recovery modelling are proposed and the problems associated with mine water recovery modelling are discussed. The paper concludes that modelling of mine water recovery, based on mine water inflow and estimated void space, can be used to give reasonably accurate predictions of recovery times and flows, but that water level monitoring is essential for precise predictions. The control of mine water during the period when coal mining was a nationalized industry was generally based on a safety first principle. This meant that when doubt existed about underground connections between modern mines and old abandoned areas of workings, mine water pumping always continued in the old areas. The result of this policy was a general lack of experience of mine water recovery and continuing doubt about underground connections. The large-scale closure of mines in the 1980s and 1990s mean that in many cases whole coalfields were abandoned and that the pumping of mine water either completely stopped or was greatly reduced. Estimations of mine water recovery made by British Coal at the time of these closures were generally based on a water inflow related to the volume of water pumped from a mine and a residual void-space calculation. The void-space was calculated using roadway dimensions for supported excavations and a figure of 10% of the original extractions thickness for unsupported (total extraction) workings ( National Coal Board 1972 ). Using this principle it was assumed that mine water recovery would proceed as a series of steps, with very little recovery when water was ‘filling’ a large void, followed by a period of more brisk recovery until the next large void was reached. The monitoring of mine water recovery by IMC Consulting Engineers on behalf of the Coal Authority (the government agency set up to look after the non-privatized areas of coal mining) has shown that, at least at large scales, mine water recovery follows precise exponential curves that appear to be independent of the distribution of mining voids. These curves are very similar to the recovery curves observed following an aquifer pumping test.

Abstract In the UK, the first longwall faces at Wistow Mine in the Selby Coalfield, with only 80 m depth of cover to the base of the Permian, experienced several inrushes of groundwater derived from the overlying Lower Magnesian Limestone, causing serious disruption to coal production. Subsequent decrease in panel width coupled with increased depth of cover to the Permian reduced the incidence of water problems. However, there has never been any quantitative investigation to determine the effects of mining on the hydraulic properties of the stratigraphically higher Permo-Triassic age Sherwood Sandstone, a major aquifer of regional importance. This opportunistic study fills that gap. Precautionary observation boreholes had been drilled above and around the margins of two proposed longwall panels prior to working the 2.5-m thick Barnsley seam at a depth of 550–600 m. Data loggers permitted continuous monitoring of the Sherwood Sandstone and Drift piezometric levels over a 2-year period. Widespread drawdown and recovery effects due to intermittent groundwater abstraction from a nearby factory were observed. Standard aquifer pumping test analyses of the hydrographs allowed transmissivity and storativity to be determined before, during and after mining. The results showed apparently permanent post-mining transmissivity increases of up to 149% around the margins of the panels, and up to 234% directly over the first panel. Post-mining storativity remained mostly unchanged. However, the greatest effects were noted during the closest approach by the second longwall panel, which also caused some additional subsidence over the first panel, when peak transmissivity increases of 1979% and storativity increases of 625% occurred. Anomalous, intra-cycle, recovery-drawdown events were also observed during this phase and interpreted as indicating rapid mining-induced dilation and compression of fractures within the aquifer fabric. The results are consistent with similar investigations carried out at relatively shallow depths (<220 m) in USA coalfields. However, the Selby study shows that mining at much greater depths still has a significant impact on shallow aquifers, with implications for enhanced aquifer recharge, abstraction well yield and possible increased contaminant transport rates.

Abstract The recent closure of the South Crofty tin mine, the last working mine of this type in Europe, has raised questions over possible environmental consequences. During several centuries of operation, the mine was dewatered by a series of pumps located at different levels in the mine. Older workings near the ground surface were dewatered by a series of adits that discharge into nearby rivers and streams. The quality of water draining from these shallow workings is generally good and no treatment is required. However, because of bad experiences at the nearby Wheal Jane tin mine, the UK Environment Agency were concerned about the quality and quantity of water which was expected to discharge from the deeper workings when groundwater rebound was completed. In order to address this problem and make predictions of the timing and volume of the discharge, computer simulations using the SHETRAN/VSS-NET model have been carried out. This model has already been applied to the simulation of groundwater rebound in several UK coalfields. However, the hydrogeological characteristics of coal mines differ considerably from the South Crofty mine. In this mine, the country rocks comprise granite and metamorphic slates, strata that have negligible transmissivity and very low storativity. Most of the groundwater flow is therefore in the ‘drives’ and stopes from which tin ore was extracted. The inflows to the mine during its operation were mapped and quantified, and were found to be mainly head-dependent. These inflows usually originated from fault zones in the rock, and also from nearby disused and flooded workings, which surround the modern mine. Predictions of the water level during rebound are compared with the observed water levels in the main shaft which have been measured since the mine closed. The model was then used to predict the dates when surface discharges could be expected to commence. One of the main limitations of the predictions was a ‘blank’ depth interval in the mine plan records, which could be interpreted in two possible ways: (i) the zone was worked in the mid-nineteenth century but the plans were lost; or (ii) the zone was never worked. Local professional opinion favoured interpretation (i), and the prediction scenarios considered most probable were based on the assumption that mining-related specific yield values would be similar in this ‘blank interval’ to those applicable in better-mapped intervals below. In the event, (ii) above appears to have been the true case, resulting in a marked steepening of the rebound curve during the later stages of rebound, with surface discharge commencing in November 2000, as much as a year in advance of most other predictions. A retrospective simulation assuming very low specific yield in the ‘blank interval’ confirms that the hydrodynamics were otherwise successfully simulated using the SHETRAN/VSS-NET code.

Abstract The strata within and above the South Nottinghamshire Coalfield dip gently towards the east. There are many abandoned shallow workings in the western area where the coalfield is exposed, but to the east the coalfield is concealed beneath Permo-Triassic strata. The coalfield has yet to suffer closure, mine water rebound and the acid mine drainage (AMD) cycle. A very large area has been exploited with complicated internal drainage systems dependent on the maintenance of existing pumping regimes. An evaluation of the AMD threat has been carried out with particular regard to the risk posed to the Sherwood Sandstone aquifer, which overlies the concealed part of the South Nottinghamshire Coalfield. The evaluation has been assisted by three-dimensional (3-D) visualization that has enabled lumping of plentiful mine abandonment data, and predictive runs using the University of Newcastle GRAM model. These studies indicate that the critical spill-over elevation is 41 m above Ordnance datum (aOD), and that the aquifer will be at risk about 20 years after pumping ceases from the Coal Measures.

Abstract Concurrent dewatering and slope depressurization operations have been underway at the Escondida open pit since 1996. A hydrogeological investigation has been undertaken as part of the depressurization operation on the north wall. It has shown that there are two distinct hydrogeological units in the slope, the altered and unaltered Escondida Porphyry. The hydrothermally altered Escondida Porphyry is clay rich and has relatively high matrix permeability. The underlying silicified, or unaltered porphyry, has very low matrix permeability and groundwater flow is in steeply dipping NW-trending fracture systems. Pore pressures in the silicified porphyry are higher than the altered material. A system of horizontal drains and vertical wells has been in operation to reduce pore pressures in the altered porphyry. To investigate effective drainage measures for the silicified porphyry, a groundwater model of the slope was constructed. This analysis showed that a drainage tunnel with horizontal drains was the most effective method of draining significant areas of the slope to the required pore pressure targets.

Abstract Hydrogeological information is crucial to the development of a sound environmental impact assessment (EIA) for a proposed mine, as well as the management of potential environmental impacts during and after exploitation. However, the determination of hydrogeological parameters is not customarily included in mineral exploration surveys, with the result that many EIAs end up being rather light in hydrogeological content. Examples from the Tarkwa gold mining district of Ghana illustrate this point. Consequences of such an inadequate hydrogeological understanding are potentially serious, ranging from an inability to predict future problems in water quality after the cessation of mining, to a lack of understanding of hydrogeological controls on slope stability, which is arguably manifest in the catastrophic spill of cyanide-rich processing effluents from a breached tailings dam at Wassa West, near Tarkwa, on 16 October 2001. To redress this deficiency, we propose that a hydrogeological database be assembled during the mineral exploration phase, according to a specified protocol (‘check-list’). Using these data, a rational conceptual hydrogeological model for the mine site and its surrounding area can be developed, providing the basis for a thorough consideration of groundwater aspects within the statutory Environmental Impact Assessment, which is (as in most other countries) required by Ghanaian government statute before a mining lease is approved. The resources required to set-up such a database are small compared to the benefits.

Abstract A general challenge to the environmental management of mine sites is the relatively high costs of site investigation and the associated development of conceptual site models and parameterization of reactive transport models. A particular problem is the inability to predict at field scale the rates of processes that give rise to long-term dissolved contamination due to active sulphide mineral weathering. Mineral weathering rates determined from laboratory and field observations generally do not agree, often exhibiting a discrepancy of two-three orders of magnitude. Recent work on mine waste deposits has demonstrated that this discrepancy can be explained by considering a small number of bulk physical and chemical properties of mine rock at field sites. The apparent decrease in mass-normalized rates between bench-scale batch reactors and pilot-scale column reactors is predicted by accounting for differences in temperature, where lower temperatures in the column reactors reduced reaction rates due to activation energy effects. The columns also contain a significantly greater mass fraction of larger particles that have lower specific surface area and, thus, exhibit lower weathering rates. The further apparent decrease in rates between the column reactors and field scale is predicted by additionally accounting for the spatial variability of sulphide-bearing rock at the site, which gives rise to only localized weathering. Localized zones of sulphide weathering are also associated with locally active weathering of silicate minerals due to lower pH. Hydrological factors are also important due to preferential flow within the field site, whereby a fraction of dissolved weathering products are retained within immobile water and do not reach the effluent stream, where ion mass flows resulting from weathering reactions are determined. These results suggest that application of compiled laboratory data to prediction of weathering rates at mine sites may be feasible. This is potentially valuable for application to Tier 1 risk assessment of mine sites, where reliable prediction of weathering rates from tabulated laboratory data would provide significant information to support the generally sparse datasets that are available, particularly for orphan mine sites.

Abstract On cessation of mining open pits or opencast workings that extend below the water table are likely to fill with water and thus develop a mine pit lake (MPL). This body of water remains as a permanent feature on the mine site and as such becomes a closure issue with respect to water quality and potential to degrade groundwater. Further, it may present a risk to the environment through the development of poor quality water with elevated concentrations of metals, metalloids, sulphate and depressed pH. The prediction of future pit lake water quality within a MPL is, therefore, essential in considering environmental impact on a closed or abandoned mine facility. The controls on a MPL will vary over time, and will involve chemical, biological and physical processes. Localized and regional-scale processes affect these in turn. Consequently, in order to predict pit lake water quality it is essential to understand the hydrogeological, geochemical and limnological processes that influence water quality.

Abstract Within the framework of a study on the impact of a mine-tailing spill at Aznalćollar, SW Spain, we investigated the oxidation of pyrite and other sulphides by means of two column experiments and reactive transport modelling. The columns were filled with pyritic sludge mixed up with a sandy and a clayey soil, respectively. The columns were located outdoors for 15 months and leached 10 times. Prior to simulating reactive transport, a flow model permitted a detailed description of the behaviour of the column at a daily time-scale. The most important parameter extracted was the hydraulic saturation. This parameter controlled the amount of O 2 that could diffuse into the soil, which, in its turn, affected the rate of pyrite oxidation. The sandy and clayey columns behaved very differently. In the sandy column, pH dropped due to the oxidation of pyrite. As a result, silicate minerals dissolved, providing Na and/or K that precipitate together with Fe and SO 4 as jarosite. The high concentration of Zn in the leachates was consistent with the concentrations predicted from sphalerite oxidation. The low As and Pb concentrations, however, were explained by their coprecipitation in the jarosite. In the clayey column, the dissolution of dolomite kept the pH high, impeding the dissolution of silicate minerals and precipitating amorphous Fe(OH) 3 in the place of jarosite. The model also permitted rate laws proposed in the literature for pyrite oxidation to be discussed. We found that the oxidation of pyrite by Fe 3+ was not faster than by O 2 , contrary reports in the literature. Finally, the model was used to predict the behaviour of other soil types and other sludge contents. According to the predictions the dissolution of jarosite was very important to maintaining the pH at a value of approximately 2, even for gravels or low reactive sand.

Abstract At present there is no suitable method to predict either the longevity of contaminant sources within spoil heaps, or the evolution of their strength over the contaminating life time of the sites. Existing acid-base accounting techniques provide little information relevant to the prediction of field contaminant concentrations and time scales. For robust prediction, the relative rates of contaminant generation and attenuation must be evaluated then extrapolated to the physical scale and environmental conditions of real field sites. Laboratory unsaturated column experiments on colliery spoil from a well-documented site in County Durham have been set up to assess its contamination potential, and the results compared with results from a mathematical model for contaminant release and transport. The random walk method, a form of particle tracking, is used to transport iron and sulphate ‘particles’, released by oxidative weathering of pyrite minerals. The model also includes the oxidation of ferrous iron to ferric iron in an attempt to account for contaminant ‘sinks’, for example where ferric iron spontaneously precipitates as ferric oxyhydroxide and is effectively removed from the transport process. In general, the modelled results compare favourably with the laboratory results and any discrepancies can be accounted for.