Remediation scenario of the abandoned Kettara mine site (Morocco): acid mine drainage (AMD) transport modeling

In this study, we present the efficiency of remediation scenario to attenuate the impact of acid mine drainage (AMD) contamination in the Kettara abandoned mine site. The study focuses on the AMD groundwater contamination of the Sarhlef shists aquifer. To predict the evolution of AMD groundwater contamination in the Kettara mine site under remediation scenario, a model of groundwater flow and AMD transport was performed.Piezometric heads were measured at the dry and wet periods from eleven wells located downstream of mine wastes. To elaborate a conceptual groundwater flow model, we faced with to the heterogeneity and anisotropy of fractured Sarhlef shists aquifer. Consequently, the study focused on the use of various approaches: 1. The inverse modeling by the CMA-ES algorithm is adopted as an alternative approach to determine hydraulic parameters indirectly, and 2. the model is treated as an equivalent porous media (EPM). The groundwater flow model was carried out in steady-state and transient conditions in the dry and wet periods using the PMWIN interface. The obtained results are satisfactory and show an excellent correlation between measured and computed heads. Contaminant transport model is used to solve the advection–dispersion equation and to generate the AMD concentration by MT3D via the PMWIN interface. A sensitivity analysis of the dispersivity coefficient is carried out. The AMD transport simulation was computed during periods of 1, 5 and 10 years, and the performed model indicates that the simulated concentrations under remediation scenario are reduced 1000 times comparing to the current concentrations. The study revealed a necessary approach in addressing an environmental issue for the AMD contamination. The results of the study will be a start-up for further research work in the study area and implementing it for the prevention of AMD propagation plume.

Hydrogeological behaviour of an inclined store-and-release cover experimental cell made with phosphate mine wastes

A field study was conducted at the Kettara mine site located in arid climatic conditions in Morocco. The goal was to assess the performance of an inclined store-and-release (SR) cover made with phosphate mine wastes to reduce water infiltration and control acid mine drainage (AMD). The SR cover was constructed using phosphate mine wastes (0.8 m) placed over a capillary break layer (CBL) made of coarse-grained materials. The SR cover had a slope inclination of 14.5°. The cover performance was monitored for a period of 1 year under natural and artificial conditions representing important rainfall events for the climatic conditions at the Kettara mine site. Performance was monitored using volumetric lysimeters, suction sensors, and volumetric water content sensors installed at four stations and at different depths. Under natural climatic conditions, the inclined SR cover limited water percolation by diverting and releasing water to the atmosphere through evaporation. However, the cover was unable to store and divert all the water at a precipitation rate >100 mm in 48 h, and percolation was observed in the lysimeters. Nevertheless, the results confirmed the suitability of phosphate mine wastes as cover material for a 31.5 m inclined (≈ 14.5°) SR cover placed over the Kettara mine wastes in natural climatic conditions and for precipitation events <100 mm in 48 h.