Assessing the feasibility of underground mining of aggregates in southern and eastern England

In the future, the provision of hard rock resources suitable for aggregates may give rise to increasing levels of conflict,particularly where they coincide with attractive landscapes or other forms of land use. Consequently licenses to operate new quarries or extensions to existing quarries are likely to become increasingly difficult to obtain. The underground mining of aggregates may become both environmentally more desirable and an economic necessity to maintain security of supply. This research examined the economic feasibility of underground mining for crushed rock aggregates in southern and eastern England, where demand for this material is high but suitable resources of pre-Permian age are absent at the surface. It sought to determine whether or not aggregates could be produced underground in the south east area of England and delivered to the local market at a cost comparable with that for surface quarries located at a greater distance. Cost models were established for aggregates production, haulage, environmental impact mitigation, health and safety, decommissioning and restoration using four different mine output scenarios. The available geological information was re-examined to identify potential areas that may contain aggregates resources at depth. With a discount rate of 10%, the lowest discounted cost of aggregate delivered to market determined across 31 prospect locations tested was £13.03/tonne, 19% higher than the reference of £10.97/tonne from a Leicestershire reference quarry producing 3.5 MTPA, and serving the same market. Capital expenditures for the most competitive underground aggregates mines ranged from 1.46 to 1.60 times the £92.63 million estimated for the Leicestershire reference case. Value generated by after-uses for the void created as well as rental revenues from concurrent development are subsequently taken into account.