Evaluating the impacts of mine dewatering and flooding on peatlands

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Mining activities, which involve the mitigation of environmental impacts, are essential to the strong economic development of Canada. Nevertheless, the links between peatland degradation and mine dewatering/flooding are not well understood. This gap in environmental assessments can lead to major environmental and financial impacts. This program targets the pre-established issue. The long-term general objective is to develop novel approaches for evaluating the impacts of mine dewatering/flooding on peatlands. The specific objectives (SO) are (1) to assess the hydrological response of a peatland to mine dewatering, (2) to evaluate the geochemical response of a peatland to mine dewatering and (3) to simulate mine dewatering/flooding impacts on peatland hydrological and chemical balance. The targeted peatland is located near the Agnico-Eagle Akasaba-West site (Abitibi, QC), where open-pit mining is expected to begin in 2018/2019. SO1 (MSc1) focuses on establishing a water budget. Loggers will be installed in piezometer nests and in the acrotelm for monitoring water levels and temperature within the saturated and unsaturated peat. Discharge and temperature fluctuations in the stream connected to the peatland will also be monitored. The data will allow an unprecedented evaluation of the hydrological response of a peatland overlying a bedrock aquifer undergoing depressurization owing to mine dewatering. SO2 (MSc2) focuses on establishing a geochemical budget. The geochemistry of peat pore water (from piezometer nests) and stream samples will be monitored during one year. In situ physicochemical parameters (including Eh and pH) will also be monitored. The analytical program will focus on the evaluation of the concentration and speciation of three main redox and pH sensitive elements (Mn, Fe, As) and on their links with variations in the stable isotopes of water (2H, 17O, 18O) and in dissolved organic carbon contents. The geochemical and hydrological data will be interpreted jointly to evaluate the linkages between peatland hydrological and geochemical balance in an area affected by mine dewatering. SO3 (PhD1) focuses on modeling. Transient hydrological simulations will be carried out using SEEP/W. The speciation of As will be evaluated using PHREEQC and Geochemist's Workbench. The transport of As will be simulated using CTRAN/W. Simulations will be conducted following a systematic parametric approach for testing the impacts of various scenarios of mine dewatering/flooding on the peatland. The program will provide novel data needed to understand the sensitivity of peatlands to mining. The approach, coupling physical, chemical and isotopic data with modeling, is original and highly relevant for the mining industry and the scientific community. The targeted mining site is expected to start operating in 2018/2019: there is a unique opportunity to initiate the program synchronously.