Integrated Mine Water Management : Stop Talking About It and Start Doing It

In an industry where many companies are targeting growth as a priority, it is becoming harder to achieve and maintain integration of technical disciplines. Whether it is a feasibility study or a closure plan, the integration of mine water disciplines is critical to quantifying risk and uncertainty, which often lies in the areas between disciplines (e.g., mine pit dewatering effects on surface water flows). Project teams that focus solely on the execution of each individual discipline without appreciating the areas where two or more disciplines overlap are doing their clients a disservice. This paper will focus on technical tools that can be used to strengthen the integration of mine water disciplines. Tools applicable to fieldwork include: • Better hydrologic/hydrogeologic datasets—Often, groundwater models overpredict baseflow reductions from dewatering because there is incomplete consideration of groundwater/surface water interactions. Groundwater models rely too heavily on the results of drilling programs and do not take advantage of other disciplines, such as hydrology and surficial geology, nor of vegetation. Temperature and conductivity surveys of surface water bodies can be used to determine groundwater recharge and discharge zones (hydrology). Test pitting within historic streambed channels can be used to determine physical and chemical streambed properties (surficial geology). Aerial or ground studies of plant distribution can be used to infer zones of groundwater discharge (vegetation). • Drive point piezometers and hydrometric stations—Piezometers can be installed to measure groundwater levels or collect water quality samples adjacent to hydrometric stations installed in surface water bodies. Hydrometric stations can be used to collect continuous surface water flow data over a period of a season or years. Free software programs are available (e.g., SepHydro) that will take the resulting hydrograph from the station and deconstruct it into baseflow and runoff components, which can be used to calibrate water models and determine groundwater discharge/ recharge zones. • Peepers (sediment porewater dialysis passive samplers)—These samplers allow quantification of contaminant transport in the vadose zone, which eliminates the reliance on surface water bodies or samples collected below the water table as the sole methods of identifying areas of contamination. • KB-Corer—These samplers allow for collection of sediment cores at the base of tailings ponds or natural water bodies to evaluate metal loadings from the water into the sediment, or vice versa, which can be used to assign source zones in water modelling. Tools applicable to desktop work include: • More robust groundwater/surface water modelling—Numerical groundwater modelling software is typically limited in that it can predict the travel times of particles through the subsurface, but it cannot be used to predict how much flow travels from the particle source to the particle receptor. New software add-ons (i.e., FlowSource) can be used to quantify how much flow originates from a particle source (e.g., waste rock pile) to a receptor (e.g., a river), which is critical in preliminary surface water assessments as a screening tool prior to more complex fate and transport modelling. • Be explicit with water modelling objectives—Often, the gaps between the various disciplines would have been identified if all water leads were involved in a project kickoff meeting where the team agreed upon the project and modelling objectives. Often, only one water discipline is the contact point for a particular scope. Still, we need to do better as consultants in recognizing that the main objective of all of our work is the protection of aquatic life. We need to always design our monitoring and modelling programs with that objective in mind, which takes an integrated approach.