Optimising closure cover design in semi-arid environments through percolation modelling and pilot trials

Authors: Ozbakir, M; Tallon, L; Hesketh, P; Ozkayhan, PO Download Paper Open access courtesy of:

DOI https://doi.org/10.36487/ACG_repo/2615_55

Cite As:
Ozbakir, M, Tallon, L, Hesketh, P & Ozkayhan, PO 2026, 'Optimising closure cover design in semi-arid environments through percolation modelling and pilot trials', in AB Fourie, G Boggs, J Heyes & M Tibbett (eds), Mine Closure 2026: Proceedings of the 19th International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 1-14, https://doi.org/10.36487/ACG_repo/2615_55



Abstract:
The design of effective closure cover systems is a critical component of mine closure planning in semi-arid environments, where overall rainfall is limited. However, episodic and seasonally concentrated precipitation events can still influence infiltration processes and long-term water quality. In Turkey, current regulatory guidance prescribes a structured, multi-layer cover system comprising, from bottom to top, a minimum 1 m non-acid-generating (NAG) buffer layer, a low-permeability barrier, a drainage layer and a topsoil cover. While this configuration is intended to minimise water ingress to underlying mine waste, its implementation on large waste stockpiles can present operational, constructability and material-sourcing challenges. This study presents an early-stage investigation program that forms part of a proactive closure planning approach, focused on the development of pilot-scale trials and a structured framework for assessing cover system performance. This timely approach is intended to enable the systematic collection of site-specific data over an extended period, thereby supporting the development of a technically sound and defensible closure cover design. The program focuses on the development of pilot-scale closure cover trials and a comparative assessment framework supported by percolation modelling. Four closure cover scenarios have been defined, including the regulatory-prescribed configuration and a range of alternative, simplified designs intended to explore opportunities for comparable infiltration management with reduced construction complexity. Representative materials for the proposed cover layers have been identified for laboratory characterisation, including particle size distribution, soil water retention behaviour and saturated hydraulic conductivity. These data are being used to inform the development of a 2dimensional percolation modelling framework, designed to support relative comparison between scenarios and guide the design of pilot-scale trials. The study highlights how data-driven and site-specific approaches can support early decision-making and constructive dialogue within Turkey’s evolving mine closure regulatory framework, while remaining aligned with regulatory objectives and long-term environmental protection goals.

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