The Consideration of Seepage-Rock Interactions on Long Term Dam Stability

The consideration of geochemical interactions within deposited materials in tailings storage facilities (TSF’s), with respect to the management of environmental impacts, is a standard state of practice in the mining industry. However, the influence of the dam seepage chemistry on the hydrologic and physical properties of the dam materials is not commonly evaluated in the current state of practice for environmental or dam management strategies.

The geochemical processes that occur at the mineral-water interface within tailings dams varies widely depending on the materials and methods used for dam construction and the physical and geochemical properties of the tailings and water within the TSF.

Two main processes can occur which effect the hydrologic and physical properties of the dam materials:
1. Dissolution of the tailings and dam material minerals; and/or,
2. Formation of secondary precipitates within the pore spaces of tailings and dams including filter materials, drains, and embankment fill.

Both these processes can alter the strength, porosity, and permeability; and affect the piezometric levels in the dam. As the long-term management of these TSFs are reviewed by the engineering community (including regulators, owners, and consulting engineers), the geochemical changes occurring within the dams that to influence dam stability and should be considered in design and management. This paper presents the main mechanisms responsible for the physio-chemical changes of dam materials, and discusses pre-emptive and forensic characterization approaches used to identify these processes.

Robertson, L. and J. Durocher. 2017. “The Consideration of Seepage-Rock Interactions on Long Term Dam Stability,” in CDA 2017 Annual Conference, October 16-18, 2017. Kelowna, BC, Canada.

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