Controls of uncertainty in acid rock drainage predictions from waste rock piles examined through Monte-Carlo multicomponent reactive transport

  • Daniele PedrettiEmail author
  • K. Ulrich Mayer
  • Roger D. Beckie
Original Paper


Heterogeneity in waste rock piles (WRPs) determines uncertainty in acid mine drainage (ARD) predictions from these deposits. Numerical modeling based on a novel and efficient stochastic framework to evaluate influential heterogeneity-linked factors controlling such uncertainty. The analysis considers a representative WRP with a mean neutralization potential ratio \(\overline{NPR} = 2\). The heterogeneity-linked factors are: (1) Scale-dependent mineralogical variability. At the “local” scale, the variability within individual rock blocks in the waste rocks (10 s of cm) is measured through the correlation coefficient (\(\rho\)) between acid producing and acid consuming minerals, here considered a geogenic property of the site. For the analyzed conditions, as \(\rho \to 0\) WRPs tend generate a higher risk of ARD and higher variability among results, which can be explained by the increasing mineralogical mixing (blending) as \(\rho\) grows. At the “field” scale, the coefficient of variation (\(CV\)) is measured as the mineralogical variability of all rock blocks within the WRP. Since \(CV\) is an engineering design parameter of a WRP, the results suggest that building WRPs with lower \(CVs\) results in less uncertain predictions of long-term neutralization capacity of the piles. (2) Flow heterogeneity. The variance of solute travel times through a pile, here measured by \(\sigma_{w}^{2}\), can be used to characterize flow heterogeneity, where high variance means stronger preferential flow in the WRP. Simulated ARD mass loadings with strong flow heterogeneity (\(\sigma_{w}^{2} \ge 1\)) leads to significant differences to the homogeneous case, increasing the uncertainty in the estimation of the ARD risk. (3) Pore gas concentration. In well-ventilated WRPs the effect of mineralogical heterogeneity is enhanced (WRPs generate much higher risk than WRPs with diffusion-limited gas transport modalities. Gas diffusion limits the amount of acidity produced in sulfidic-rich zones, thus attenuating the effect of mineralogical variability at the scale of the WRPs compared to well-ventilated piles.


Stochastic modeling framework Mining waste rock piles Uncertainty Multicomponent reactive transport modeling Geostatistics Acid rock drainage 



All data used to perform the simulations are available after requested to the corresponding author (DP).

Compliance with ethical standards

Conflict of interest

The authors declared that they have no conflict of interest.

Supplementary material

477_2019_1756_MOESM1_ESM.pdf (608 kb)
Supplementary material 1 (PDF 608 kb)


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Dipartimento di Scienze della Terra “A. Desio”Università degli Studi di MilanoMilanItaly
  2. 2.Earth, Ocean and Atmospheric SciencesUniversity of British ColumbiaVancouverCanada

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