A simple, low-cost approach to predicting the hydrogeological consequences of coalfield closure as a basis for best practice in long-term management

Abstract

A simple, low-cost approach to predicting the hydrogeological consequences of coalfield closure as a basis for best practice in long-term management. International Journal of Coal Geology, 164, pp. 25-34. (doi:10.1016/j.coal.2016 This is the author's final accepted version.There may be differences between this version and the published version. You are advised to consult the publisher's version if you wish to cite from it.http://eprints.gla.ac.uk/120112/ The closure of individual coal mines usually entails a cessation of mine dewatering, which can give rise to significant changes in the local and regional hydrogeological regime. Where the last colliery in an entire coalfield closes, these changes can be very large-scale and potentially damaging, with potential for pollution of major rivers and aquifers. While a number of modelling approaches have been developed in recent decades to predict these changes and facilitate their proactive (and prophylactic) management, when the last mine in a given coalfield is closing the mine owners typically have neither the time nor money to commission extended and sophisticated numerical modelling studies. In such circumstances, a simplified, lower-cost approach is required to provide regulators with predictions of rates of water level rise, future equilibrium water levels and the rates and quality of any future outflows of mine water to rivers and / or aquifers. These predictions can also be useful in guiding the decisions of future site owners over alternative uses of colliery infrastructure after the cessation of coal production. An approach to such predictions has been developed which is based on summary information on the extent of workings, dewatering pumping rates, locations and collar elevations of unfilled shafts and adits attached to the deep workings, as well as surface topography and the geometry of any overlying aquifers. Uncertainties over hydraulic gradient after the completion of water level recovery are handled by analogy to a range of postrecovery gradients from similar large coalfields. A brief example of the application of the approach to a real coalfield is presented. This approach could be used either on its own or as a prelude to more detailed modelling and monitoring during the years following mine closure. The insights into system behaviour gained from such exercises could well be valuable in future re-use of flooded voids as resources for heat recovery or disposal as part of low-carbon heating systems. Highlights• Prediction of the hydrogeological behaviour of abandoned coalfields • Quantifies the duration of flooding till rest water levels are reached • Identifies the mined features most likely to give rise to polluted outflows • Allows prioritisation of post-closure treatment of major shafts

Approaches of Applying Non-Darcian Flow Equations to Predicting Groundwater Rebound in Response to Coal Mine Closure

“…In many abandoned mines, the mine voids consist of un-mined materials. The value of S ranges from 0.01 to 0.5 with an average of 0.3 for closed mines in the United Kingdom (Younger 2016). Based on authors" experience in China, the value of S depends on type of rock in the overlying formations and mining method associated with coal recovery rate.…”

Stability Analysis of Shafts Used for Minewater Heat Recovery

“…Three different water levels (-50 m, -150 m and -300 m) are analyzed. The hydraulic gradient of groundwater towards the shaft is set as 6 9 10 -4 according to Younger (2016) who studied the hydrogeological consequences of coalfield closure. Although change in hydraulic gradient will induce different stresses, the range of hydraulic gradient is very small.…”

Conceptualization and finite element groundwater flow modeling of a flooded underground mine reservoir in the Asturian Coal Basin, Spain

“…Managing of environmental risks during and after coal mine closure is an important matter of concern in a scenario in which many exploitations have closed, or will do soon, in Europe (Didier 2009;Klinger et al 2011;Bondaruk et al 2013;Younger 2016). Such is the case of numerous mines in Asturias, Spain (Moreno and López 2008;Jardón et al 2013).…”