I have recently posted two EduMine courses: Surface Water Management at Mines and Groundwater in Mining. Here is something from Wardrop that I wish I had added to the course on groundwater. It will just have to wait for the update.

The conceptual design of a new dewatering system requires the integration of several criteria. Relying on traditional water balance is not sufficient for system design and equipment selection. It requires a thorough analysis of how final decisions will be impacted. The following must be identified:

Water consumption by operating equipment averaged over a period of time – This varies within the mine plan by location of active workings, the chase for the ore veins, and by the necessity for infrastructure development.

Water consumption by operating practices – This includes allowances for dust suppression, cleaning equipment, spillage, and excess water from different backfill and shotcrete operations.

Water infiltration from the surrounding environment – This includes escalating infiltration due to faults and other ground discontinuities, which increases as the mine ages and expands, as well as insidious leakage due to rock and soil types. The volume is dependent upon the existing geological conditions and can be predicted. This volume can fluctuate seasonally which must be accounted for in determining the pump’s final capacity. and operate the system to failure. If the mine life can be projected over a longer period of time, it may be more practical to select a system that can be maintained and expanded as required.

The system must then undergo economic reviews that will impact pump selection, as follows:

Mine geometry – The target depth of the mine and the timeframe are most significant. If numerous level developments are anticipated, then the head requirements can be split over a number of pumping stations. If fewer pumping stations are required, then the head development requirement for each station increases.

Level geometry – The most significant of these is the space allocated for the pump and pumping station including the power and control requirements, the sump, and the solid separation system. If space is available, it may be prudent to install sumps of sufficient size to separate solids and then pump only clear water. A solid separation system requires a plan to remove the collected solids, and a separate plan that identifies what to do with them once they are removed. It is not uncommon for a clear water pumping system to fail due to undersized settlement sumps or properly sized settlement sumps that are not cleaned as required.

The life of the mine – Should the mine have a predictable short life, it may be prudent to define the dewatering system as disposable, perform little or no preventative maintenance, and operate the system to failure. If the mine life can be projected over a longer period of time, it may be more practical to select a system that can me maintained and expanded as required.

Slime production – The quantity and size of the anticipated slimes is important. Exposure of the water to these slimes, or to the ore, may change the chemical nature of the water, creating specific pump and pipe selection criteria. Should the analysis determine it to be prudent to pump the slimes, then pump-type criteria will also be impacted.

Disposal of slimes – If the slimes contain an economically recoverable ore, then one decision may be to pump slimes either as they occur or in a thickened state to a processing facility, dealing with the gangue after further processing. It must also be determined if the disposal of the slimes is environmentally hazardous, in which case, this must be addressed in the planning stage.

Consideration must also be given to pipes including material, thickness, connections, and sizes, as well as overall efficiencies, motor voltages and currents, and equipment standardization, all of which play a role in determining the final system to be used.