Mining and environmental factors in selecting an underground versus a quarry mining system
Historically, the decision on whether to mine by underground or surface methods has been based on mining and economic considerations. This is rapidly changing since the environmental imperatives that have evolved over the past two decades are now a critical part of the decision process. As a result, quarry operations are increasingly considering the option of going underground. This research was carried out to identify the factors which would cause a surface quarry operator to consider the transition to underground mining.
To identify the major incentives for going underground, primary factors influencing the decision for selecting underground mining over continued quarrying were investigated. Analysis of the literature and data gathered from site visits showed that significant benefits could be gained from mining underground, with respect to selected economic factors, environmental permitting and legal compliance, and post-production site usage for continued income.
To determine mining characteristics of the typical surface quarry, data on the production phase (mining sequence) and environmental problems was collected from 18 quarries at various stages of their operating life spans. The data was obtained from sites in the Appalachian region of four states: Virginia, West Virginia, Maryland and Tennessee. Corresponding data was also gathered from successful underground operations to determine the values for a typical underground mine. Comparisons of this information indicated that the biggest differences between surface and underground operations existed in: the drilling and blasting phase, and in the haulage phase of the mining sequence; the size of the equipment; the extent of environmental concerns; and the potential for post-production income from the site.
The process of environmental risk assessment was reviewed as a supporting tool to aid in the selection of underground over surface mining. By assigning probabilities of failure to specific, independent, environmental hazards, an operator can evaluate and compare the likelihood of success or failure operating as a quarry or underground mine. A case study from the data collected was used as an example to show how the procedure can be practically implemented.