The role of pore-gas dynamics in guiding reclamation practices

The storage and transportation of pore gasses in overburden and reclamation soil covers were evaluated using statistical analyses and finite difference numerical modelling to guide mine operators regarding practical issues surrounding the construction of overburden landforms, design of soil cover systems and management of reclamation sites. Factors that were found to impact gas transfer were soil moisture, soil temperature, differential pressures and dry bulk density of the overburden landform. Furthermore, the construction of the overburden landform appears to be more impactful to pore-gas dynamics than the design of the soil covers. Practicable recommendations can therefore be inferred to facilitate simultaneously methane oxidation in the uppermost horizon of the overburden while maintaining sufficient pore-gas oxygen in the plant-rooting zone of the soil covers to facilitate growth and survivability of reclamation vegetation. It is recommended that overburden be placed to approximately 1·6 Mg/m³. Mine operators should also recognise and manage extreme moisture conditions in the soil covers and uppermost overburden to mitigate restrictions in gas exchange and methane oxidation.