Clifton at IAH-CNC Waterloo 2015
The Canadian National Chapter of the International Association of Hydrogeologists is hosting the 2015 Canadian Conference in Waterloo from October 27 to 30, 2015. The conference theme is simply "Canadian Hydrogeology". The technical program will span the range of current hydrogeological issues in Canada – from the latest research to advances in professional practice. Hydrogeology is a maturing science in Canada, and the conference will provide a great opportunity to learn and connect Canadian hydrogeologists to each other and to the wider IAH community.
Clifton's Terryn Kuzyk is presenting the following paper:
A Conceptul Model for Pore Water Release from Coal Waste Rock Piles in the Elk Valley, British Columbia, Canada Terryn Kuzyk, Clifton Associates; S. Lee Barbour and M. Jim Hendry, Department of Civil and Geological Engineering, University of Saskatchewan (Saskatoon, Canada)
The open pit mining of coal results in the formation of new landforms constructed from waste rock. Rock drains, either constructed or formed during dumping by natural segregation, underlie some of these landforms. Constructed rock drains are often designed to convey surface water from higher in the watershed through the waste rock dumps. Rock drains also collect water moving through the waste rock and convey it to adjacent surface and ground water. Long-term monitoring of the chemistry of water conveyed by rock drains provides an opportunity to characterize the rates of flushing of these constituents through the waste rock piles. In this study, a conceptual model for the long-term release of nitrate (NO3), selenium (Se), and sulfate (SO4) from coal waste rock piles is developed and used to interpret monitoring data from eleven rock drains of varying ages in the Elk Valley, British Columbia. The hypothesis of the conceptual model is that the flushing of the first pore volume of water within the waste rock can be characterized by NO3 release. The NO3 is derived from blasting and is considered to be a conservative species. The first pore volume will also contain SO4 and Se generated by oxidation of waste rock during blasting and pile construction. Post-depositional oxidation and production of SO4 and Se are identified by the evolution of the effluent signature from an initial SO4/NO3 ratio, representative of the initial pore fluid at deposition, to an increasing SO4/NO3 ratio as the initial pore volume is released and Se and SO4 are produced by oxidation. This hypothesis is tested by interpreting the patterns of NO3, SO4, and Se release as described by SO4/ NO3 and Se/SO4 ratios. In cases where upstream sources are contributing to the observed flow and concentrations within the rock drain, an attempt is made to correct the monitoring data so that it represents only the contribution from the waste rock overlying the rock drain. The concentrations of NO3 and SO4 were found to correspond to differences in the chronology of waste rock placement, while the Se/SO4 ratios were relatively constant and consistent with ratios associated with oxidation. A model of the evolution of the effluent chemistry was developed using a system dynamics model comprised of stocks (water storage) and flows (flushing) within blocks of waste rock placed at various times within a watershed. The model illustrates how stored water volumes, rates of flushing, production rates, dump chronology, and, where applicable, upstream sources control the evolution of rock drain chemistry over time. The goal of this work is to develop methods of evaluating the impact that various dump designs might have on the timing and magnitude of NO3, Se, and SO4 releases.
Session: Groundwater Issues From Mining and Aggregates