Performance of engineered test covers on acid-generating waste rock at Whistle mine, Ontario

Abstract

This paper presents the design and 3 year field performance results of three engineered test soil covers for the mitigation of acid rock drainage (ARD) at Whistle mine near Capreol, Ontario. Each test cover was a two-layer system consisting of a 0.90 m noncompacted pit-run gravelly sand overlying a barrier layer. The three barrier layers studied were a 0.46 m thick mixture of sand (92%) and bentonite (8%) (SB), a 0.60 m thick layer of sandy silt with about 5% clay (SS), and a 0.008 m thick geosynthetic clay liner (GCL). Each cover was installed on 6.10 m thick acid-generating waste rock and was instrumented and monitored along with a control test plot that consisted of 6.10 m of waste rock. The ultimate objective of the study was to select a suitable cover for full-scale decommissioning of acid-generating waste rock backfilled into the Whistle pit. Results from 3 years of monitoring showed that the GCL was the most effective barrier in reducing percolation into the underlying waste rock. Percolation through the GCL barrier was 7% over the 3 year period compared with 20% and 59.6% through the sand–bentonite and sandy silt barriers, respectively, and 56.4% through the control plot. The overall quality of percolate water from the covered waste rock was much better than that of percolate water from the uncovered waste rock. Aqueous geochemical modeling suggested that percolate water draining the oxidized waste rock was controlled by hydroxides, oxide, and sulphate phases of Al, Ca, Mg, and Fe3+.Key words: waste rock, acid rock drainage (ARD), capillary barrier, geosynthetic clay liner, amended soil systems, percolation, MINTEQ.

Design of a Dry Cover Pilot Test for Acid Mine Drainage Abatement in Southern Brazil. I: Materials Characterization and Numerical Modeling

“…• Step 2: numerical modeling of the cover system performance at the specific local climatic conditions. • Step 3: pilot testing at the site with adequate instrumentation for monitoring the cover performance under field conditions, such as described by Adu-Wusu and Yanful (2006); Wilson et al (1995); Woyshner and Yanful (1995); Yanful et al (1993).…”

Prediction of the water balance of two soil cover systems

“…Volumetric water content, soil suction, soil temperature, percolation, runoff and interflow were also measured. Detailed description of the test plots and instrumentation are given in O'Kane Consultants Inc. (2001) and Adu-Wusu and Yanful (2006). Monitoring and evaluation of the performance of the plots was conducted over a period of approximately 4 years (October 2000-August 2004 and are reported in Adu-Wusu and Yanful (2006).…”

“…For covers used to minimise production of acid rock drainage, high water content of the barrier is needed to maintain at least 85% degree of saturation, to minimise the diffusion of oxygen to the underlying waste rock (Yanful et al 1993(Yanful et al , 2003Benson et al 1994;Adu-Wusu and Yanful 2006). On the other hand, the infiltration of water through the barrier layer to the underlying waste in mining and some landfill applications may lead to the flushing of contaminants into the groundwater system.…”

Avaliação em laboratório do uso de sistemas de coberturas alcalinas para prevenção da drenagem ácida de mina

“…na remediação são aplicadas técnicas de contenção e, ou, tratamento, as quais podem ser classificadas como ativas ou passivas, de acordo com a existência ou não da necessidade de introduzir energia no sistema para inicializar e continuar o processo (blowes et al, 2003;Johnson & Hallberg 2005;Akcil & Koldas, 2006). Uma alternativa de prevenção é o uso de coberturas secas (bussière et al, 2004;Adu-Wusu & Yanful, 2006;soares et al, 2009). essas coberturas têm por objetivo principal o controle da entrada de oxigênio e água, inibindo o processo de oxidação de sulfeto na sua origem (souza et al, 2003).…”