M E M O R A N D U M development to get deep in the mine, risk free, and to allow for dewatering/grouting activities to be more effective in a safe manner. Dividing the mine by RL's into different water producing zones by relating K Values to each area is a start. Relating this K value to a flow factor with pressure then assigns a potential flow expected. Major known faults will also be potential water sources and/or potential water boundaries for different zones. It is therefore it is important when mining to cross-cut these faults perpendicular, if possible, so grouting costs are minimized. The many lenses/faults at WUG are assumed to be compartmentalized aquifers with high conductivity. Potentially from exploration diamond drilling they are now areas of equal conductivity. Hangingwall and Footwall connection between these areas needs to be fully understood. This can be done with data points in each of these areas, (either grouted piezometers or pressure transducer loggers). If there are differences in pressures or conductivity between lenses, then each of these areas can be nominated as potential zones. This Zone matrix will be used directly in the mine design process and all designs must relate to it and be signed off as such. They will use the matrix to determine the likelihood of water intersection, determine the likely pressure, calculate and determine the consequence of water intersect, determine the risk and recommend the level of precaution. Technology allows for the Piezometers and Loggers of the surface critical water level monitoring points to be linked in real time to the server and notifications of pressure change can be sent if required. For example: If development drilling intersects a fault and allows water to flow for a period before stopping the water, if this fault is connected to the surface the piezometer will show the dip and send a notification in real time if required. The water zones are put on the survey memos so that miners are aware of risks as well. Attached is a memo from Ernest Henry mine that explains the purpose of their Water risk matrix and gives examples of how zones were identified at that mine. At EHM this Matrix was used successfully to give operations the confidence to put actions in place when entering certain zones to diminish risk of water inundation. Similarly at the OceanaGold Didipio project water zones were developed to better understand flowrates from the orebody. Certain areas required high pressure grouting other areas relied on pumping (dewatering) to get through. Some areas designs were changed to avoid certain zones.
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