There’s no hiding the fact that effective mine dewatering is key to an efficient mining operation.
As we delve deeper into the Earth’s crust and the ingress of water into the operating mine increases, is it enough to just add more pumps to the system to get the water out? This reactive approach is all too common. With a ‘daisy chain’ of pump stations of different makes, sizes and duties desperately trying to keep our feet dry.
How can we improve our approach to mine dewatering and what are the benefits?
There should be a push for mine owners who are setting up a mine or implementing a new Primary System to push for ‘flexible’ systems that include monitoring systems where practical. In this day and age of big data and where costs for instruments are continuously reducing and becoming more affordable, such instruments can provide a significant amount of information as to the performance and status of a system and enable its users to determine its efficiency, utilisation and how it is serving the original design criteria. If set up in a flexible manner, it will enable the operator to make quick and effective changes and ensure the system can be constantly adjusted to suit the ever-changing conditions of the site.
Dewatering accounts for a significant power consumption cost in a lot of UG mines globally, and also in operating maintenance and service costs. A lot of sites develop a Life of Mine (LOM) plan as part of the Definitive Feasibility Study phase or at least early within the commencement of the mine life. Whilst it is not always practical to completely change a primary dewatering system in an operating mine for obvious reasons (and some not so obvious), there are many ways in which operating systems can be improved/modified/upgraded etc. to be optimised and suit the ever changing mine. Particularly where we now see a trend for mine life extensions and resources being expanded as a result of buoyant metal prices – it’s these mine sites that will really benefit from reviews of their dewatering & operating systems.
Attack the source not the symptom.
Rather than passively dewatering, careful consideration should also be made in investigating whether there are methods to actively stop water from entering the mine (or at the very least diverting water to areas away from working heading). One method that we have found to be successful is via the installation of dewatering bores underground to achieve localised lowering of the water table. These bores can be localised around the periphery of active developments so as not to interact with equipment, and can be installed in advance of development, ensuring water ingress will not be an issue.
Other methods include the use of high pressure grouting (if ground conditions allow) to create impermeable “screens” which divert water away from active underground developments. By using pre-excavation grouting, risks of water inrush can be eliminated and poor and unstable ground conditions can all be approved, whilst sealing developments off from water ingress.
“the importance of regularly and periodically revaluating a mines dewatering system to ensure optimum performance and efficiency can’t be ignored”
As mines get deeper, the use of recycling systems underground has become more pronounced. By recycling the water underground, the amount of water that needs to be evacuated from the mine is reduced. Recycling system technology has reached a point where the creation of ‘raw’ and even potable water can be produced underground at costs much lower than if the water had to be removed completely. Modern modular systems similar to the IMEC designed recycling plant pictured, can be designed to suit the mines parameters and simply plugged into the system minimising disruption to operations.
Given advances in UG communication bandwidth and the increase in competition of vendors supplying connected devices, automation of dewatering systems has become incredibly cost effective. By including an automation philosophy as part of their design criteria, dewatering systems can be developed so they can not only accurately track and trend system performance, but also allow for automated redundancy operations. By automating redundancy in the system, down time in operations due to flooding, or pump failures can be reduced, leading to overall savings for the mine.