Johnson, B, Gale, J, Mejia, R, Veneklaas, E, Leopold, M, Erickson, TE, Drake, P, Gibson, D, Stock, E, Springer, D & Alzetta, L 2025, 'Optimising revegetation for mine closure: initial learnings from a multi-faceted approach 
to minimise net percolation using native vegetation', in S Knutsson, AB Fourie & M Tibbett (eds), Mine Closure 2025: Proceedings of the 18th International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 1-9, https://doi.org/10.36487/ACG_repo/2515_73
(https://papers.acg.uwa.edu.au/p/2515_73_Johnson/)
Abstract: Acid mobilisation due to net percolation (NP) through overburden storage areas poses a significant water quality risk at closed mine sites. Our research program aims to optimise cover system performance to minimise NP and associated acid mine drainage (AMD) risk at BHP’s Mt Whaleback operation in Western Australia. Recognising vegetation as crucial for reducing NP, the Revegetated Cover System Program (RCSP) investigates vegetation–substrate interactions to inform and guide closure commitments.
The RCSP encompasses five tasks:
controlled NP experiment (small-scale)
controlled species assemblage, transpiration, and NP experiment (small-scale)
large-scale revegetated cover system trial
mature rehabilitation physiological monitoring
natural analogue physiological monitoring.
This paper presents initial findings from a multi-year research program investigating the role of revegetation in minimising NP and mitigating ARD risk at BHP’s Whaleback operation. The program aims to optimise cover system performance by quantifying plant water use and its influence on NP under various scenarios. Initial results from controlled experiments demonstrate the importance of substrate properties and irrigation regimes on soil moisture dynamics and NP. Analyses from the first year of the large-scale revegetated cover system trial, including lysimeter and plot-based measurements, will be presented. These data will 
provide insights into vegetation establishment, growth rates, and early indications of plant water use. 
Preliminary findings from physiological monitoring of mature rehabilitation and natural analogue sites will also be discussed.
This research program is crucial for developing science-based solutions to achieve vegetation communities that are comparable to natural analogues and that provide fit-for-purpose function. By integrating these findings into cover system design and management practices, BHP aims to significantly reduce AMD risk and contribute to long-term environmental sustainability.

Keywords: ecosystem restoration, acceptable risk and failure modes, closure objectives