M E M O R A N D U M To: Euan Leslie, OceanaGold Pere White, Grouting Specialist Alexis Valenza, Valenza Engineering Peter Gribbin, Valenza Engineering From: Joe Evert, Mineright Date: 24/04/2022 Subject: WUG Operational water management guidance The key questions that operations require to be answered is how much water (l/s), where it is likely to be intersected, and at what temperature and pressure (kPa) it will be? With this information design and planning can ensure that engineering safeguards are in place for risk mitigation. It most mining cases the trade off between grouting and dewatering is usually an economic decision. Whether to drawdown the aquifer with a pumping system to keep the operation dry or pressure grout the structure and not pump as much. The WUG project specifies that drawdown of the aquifer (to surface) is a prerequisite of effectively zero. The hydrogeology department effectively has to have monitoring in place to a. Set boundary zones for areas of likely water intersections and hydraulic conductivity of such zones. b. determine the relationship between water intersected underground and the surface in each of these zones c. Set boundary limits for acceptable leakage during mining. d. Set boundary limits for dewatering in each of these zones. Mine water Zones In an attempt to relate important hydrogeological data and the effect it has on the operation or is having on underground mining in a way that can be understood by the mining department and relevant authorities, developing a Mine Water Zone and a water risk Matrix is a great tool for assisting in the decision-making process and mine design. This tool allows for pressure grouting designs to be planned out in zones. It can be updated as new information comes to hand as each new hydrogeological hole is drilled or data on permeability comes to hand. It allows more people to be aware of the constraints that they will need to design to in different areas of the mine. It also creates a step in the design process for less experienced personnel to adhere to. This tool, once developed, is an effective way for relating water inundation risk to proposed development by using existing knowledge of water pressure and current intersects in areas already mined underground. It also gives a clear picture on where there are gaps in our understanding and makes us seek answers to areas of concern or areas where there is no information. A key outcome of this tool is also developing an area of the mine that is known to be dry. This Dry zone allows for development to occur at normal development rates and costs. It allows for
RkJQdWJsaXNoZXIy MjE2NDg3