Field experimental cells to assess hydrogeological behaviour of store-and-release covers made with phosphate mine waste

Abstract

A field investigation was conducted to evaluate the effectiveness of store-and-release (SR) covers made with different phosphate mine wastes in reducing water infiltration (system inclination and surface runoff were neglected) and controlling acid rock drainage (ARD) generation. Four instrumented experimental cells were constructed with different SR layer configurations (two thicknesses and three materials) placed over a capillary break layer. To assess the hydrogeological behaviour of these cover systems, volumetric water content, matric suction, and meteorological monitoring time trends were studied for a period of 1.5 years under actual and extreme conditions typical of an arid climate. Under natural climatic conditions, all net infiltration was released to the atmosphere by the physical process of evaporation (regardless of SR layer thickness and type). Although high surface matric suction (>3000 kPa) decreased the evaporation rate (or release capacity) during the drying period, field tests showed that the studied scenarios limited deep water infiltration even under extreme rainfall events. The release capacity of the SR layer was slightly lower for cover systems made with the finer-grained mine waste (phosphate limestone tailings). This study showed that, for a one-dimensional (1D) condition, the tested phosphate mine wastes have the appropriate hydrogeological properties to be used as components of SR covers under conditions at the Kettara mine site, located near Marrakech, Morocco.

Phytostabilization of Phosphate Mine Wastes Used as a Store-and-Release Cover to Control Acid Mine Drainage in a Semiarid Climate

“…This cover system allows the reduction of water infiltration and is considered to be one of the least expensive and most promising technologies, adapted to dry climate countries like Morocco ( Figure 1 ). The tested SDR cover system consisted in covering the AMD generating wastes with a 1 m layer of phosphate wastes that reduced water infiltration and, effectively decreasing AMD production [ 8 , 9 , 10 , 11 ].…”

Review of the Reclamation Techniques for Acid-Generating Mine Wastes upon Closure of Disposal Sites

“…Such so-called store-and-release (SR, or alternate) covers have been shown to be quite efficient at reducing the quantity of water reaching the underlying waste, provided that the right materials are used to create the required capillary barrier effect (described below) and storage capacity. This type of cover has been constructed at the Barrick Goldstrike operation in Nevada, USA (Zhan et al 2000), and also applied within experimental cells at the Kettara mine, Morocco (Bossé et al 2015).…”

Mine Drainage Generation and Control Options

“…Passive Treatment. Store-and-release (SR) covers made with different phosphate mine wastes were studied for their effectiveness in reducing water infiltration and controlling AMD generation in a field investigation (Bosse et al, 2015). It was found that the studied scenarios limited deep water infiltration and the tested phosphate mine wastes had the appropriate hydrogeological properties In the USA, a dry flue gas desulfurization (FGD) product was investigated for abandoned coal mined land reclamation (Chen et al, 2015a).…”