The impact of mine dewatering on the hydrology and mercury bioeochemistry of peatlands in the Hudson / James Bay lowland: The De Beers Victor Diamond Mine

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Diamond mining operations near Attawapiskat, Ontario are set to begin in early 2008. Over 90% of this area is covered by peatlands (muskeg). Dewatering of the mine will pull water from the underlying permeable limestone aquifer that could cause or accelerate downward seepage of water from the surface system, and partially drain about 3000 km2 of peatland. We anticipate distinct spatial patterns of drainage related to the strength of the connection between the upper and lower hydrological systems. Relatively permeable bioherms (ancient coral reefs) that protrude to the surface from the bedrock aquifer through the layer of fine-grained sediments that directly underlie the peatland, are expected to provide "windows" of seepage. Where partial drainage of peatland occurs the ecosystem will change, notably the vegetation patterns. DeBeers has made a substantial financial contribution to a research project which aims to explore and document the hydrogeological linkages between the surface (peatland) and deep (limestone) aquifer systems. The current proposal builds on that research by 1) examining in more detail the peatland drainage systems (water table, soil moisture, flow pathways) so we can construct a water budget that includes a range of peatland types; 2) investigating the mercury dynamics in this system, since we suspect that the disturbance will cause methylization of the naturally occurring mercury, hence its liberation into surface waters; and 3) expanding the scale of disturbance-monitoring with the addition of a remote sensing component which will detect changes in water-sensitive vegetation communities and peatland surface configurations - and thus allow us to interpret the broader impacts and responses of the mining activity.