A phased approach to mine dewatering – updated from IMWA 1993 (2024)

Kym L Morton
KLM Consulting Services Pty Ltd, 22 Central Road, Lanseria, 1748, South Africa

Abstract
Mining often requires penetrating the local and regional water table. This creates inflows, which if the area is wet and the country rock highly permeable, becomes at best a nuisance to operations and at worst an extreme hazard. Effective dewatering creates dry working conditions which are preferable as they reduce risk, reduce wear and tear on machinery, reduce earth moving costs, improve slope stability for open pits and therefore improve safety. Dewatering success is directly linked to a detailed understanding of the groundwater regime enabling application of the best strategy to intercept groundwater inflows. Options available are both passive and active methods including detailed stormwater design, drainage trenches, drain-holes, pit-perimeter pumping boreholes (wells), in-pit boreholes, sumps, dewatering galleries, or a combination of methods. A phased approach assists with logically managing the data, information and knowledge for use in dewatering design and implementation.
The potential effects of groundwater inflows should be assessed at the pre-feasibility stage but can be done at any stage of the mine life. A hydrogeological investigation is best tackled in three phases. The first phase is a desktop study to identify the problem, collect site data, create a detailed initial conceptual hydrogeological model then use the information to identify the most practical options for water control.
Phase 2 comprises numerical modelling of the conceptualisation, supported with accurate and interpreted monitoring data. The objective is to use predictive simulations of dewatering options to determine the best strategy for water control. Phase 3 sets dewatering targets to support the mine design, creates an initial dewatering design then implements a prototype to test the concept. Success is evaluated, and the design improved to increase efficiencies and enable full implementation. The phased approach is iterative as the conceptual and numerical models are regularly updated, recalibrated with the latest monitoring information, and used to review and implement the dewatering strategy. The monitoring network is continually improved, and the phased approach repeated annually to ensure water control objectives are met for each stage of mining. This paper is an update of the IMWA paper Morton et al. (1993) which is still widely read.

Keywords: Mine dewatering, conceptualisation, numerical modelling, dewatering methods, dewatering scenarios.

Morton, K.L. (2024) ‘A phased approach to mine dewatering – Updated from IMWA 1993’, West Virginia Mine Drainage Task Force Symposium & 15th International Mine Water Association Congress, pp. 458–463.