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Progressive abandonment of the South Nottinghamshire Coalfield raises concerns over the security of the Permo–Triassic Sherwood Sandstone aquifer which overlies the concealed part of the coalfield. A 3-D digital visualization package has been used to assemble and display the complex and diverse data-sets of relevance. Predictive scenarios have been run from these data using the University of Newcastle program GRAM (Groundwater Rebound in Abandoned Mineworkings). The work comprised three phases: (i) confirmation of the geological framework for the so-called ‘Pond 3’ area (southernmost part of the coalfield) and establishment of a water balance along with an outline groundwater flow path system for the Coal Measures and adjacent strata; (ii) the collation of detailed geometric information on the spatial distribution of discrete geological layers that are considered to have hydrogeological significance, the distribution of mineworkings within key horizons, and the locations of boreholes, shafts and pumping stations (both in the Coal Measures and within overlying strata). Possible flooding configurations have been assessed geometrically to identify ‘hot spots’ where mine water discharge to surface may occur, and areas where the piezometric level of the rising mine water might promote upward fluxes into the Permo–Triassic Sherwood Sandstone aquifer. In addition, critical areas where coal has been worked close to the base of the Permian and where hydraulic continuity may occur between the Sherwood Sandstone and Coal Measures have been identified; (iii) the GRAM model used data held in the 3-D visualization package VULCAN to define discrete ‘ponds’ within the coalfield. Recharge to the system allows each pond to fill until overflow pathways are reached, when the adjacent pond may start to fill. A variety of such scenarios have been completed and predictive data generated, which suggest that possible discharge to surface and into the Sherwood Sandstone might occur about 20 years after the end of dewatering.

The South Wales Coalfield is structurally and lithologically complex. Attempts to understand the regional groundwater flow system have been largely piecemeal, focusing on single collieries or groups of collieries. Inspection of both historical data, gathered during the active mine dewatering phase of the coalfield, and of contemporary post-mining groundwater rebound data, allows a picture of the whole groundwater flow system to be derived, along with the regional water balance. The assessment is aided by application of a 3D visualization model of the geological framework, which includes the piezometry during and after the mining phase and pumping and yield data. Other valuable historical information, which can no longer be replicated, are the analyses of samples of groundwater that entered working mines from specified horizons, rather than present-day analyses of acid mine drainage. It is found that there is little deep regional groundwater flow across the basin, for example towards the sea, and most groundwater flow is of river catchment scale draining to the main rivers that traverse the coalfield. This analysis of the coalfield and the 3D model provide a foundation for future investigation into issues such as dewatering of new opencast pits, in situ gasification or anthracite mining.

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 550-600m. 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.

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