Findings of International Review of Soil Cover Design and Construction Practices for Mine Waste Closure

Abstract

Abstract. Selected results of an international review of soil cover design and construction practices and performance is presented in this paper. The review, which was carried out in 2003, initially included 177 case studies in 14 countries. This has subsequently been updated to include more than 200 individual case studies. The case studies include soil covers for tailings impoundments, waste rock piles, backfilled pits and heap leach pads. The mining operations included precious metals, uranium, coal and oil sands. This is the first international review to focus on the practical questions related to soil cover construction practices, and specifically how that relates to long-term cover performance. This paper provides some suggestions as to how operators, regulators and practitioners could improve soil cover design and construction practices, as learned from these actual case studies.

Improving performance of soil covers over waste rock dump tops in dry climates

“…The evolution of the soil cover design methodology and principles applied to mine waste rock can be traced through Yanful andLin (1998), O'Kane andWels (2003), Rykaart et al (2006), and the Global Acid Rock Drainage Guide (GARD Guide, 2009), all of which have a North American, or even Canadian, focus. Each of these publications presented similar leading-practice processes for soil cover system design; those described by Rykaart et al (2006) and the GARD Guide (2009) are presented in the following sections. Rykaart et al (2006) presented a refined 12-step procedure, which is reproduced in Figure 1.…”

“…Each of these publications presented similar leading-practice processes for soil cover system design; those described by Rykaart et al (2006) and the GARD Guide (2009) are presented in the following sections. Rykaart et al (2006) presented a refined 12-step procedure, which is reproduced in Figure 1. The authors made the point, based on 200 soil cover case studies worldwide, that few mines documented the reason for constructing their soil cover, and very few case studies rigorously followed the full procedure reproduced in Figure 1.…”

“…Kidston Gold Mines in north Queensland, Australia (Williams et al, 1997(Williams et al, , 2006, Barrick Goldstrike Mines in central Nevada, USA (Zhan et al, 2006), Les Terrains Aurifères in Québec, Canada (Ricard et al, 1997), Whistle Mine (Ayres et al, 2002) and Wismut (Diehl, 2011) are among the rare examples. Rykaart et al (2006) noted an apparent disconnect between mine closure objectives and the selection of mitigation measures (such as soil covers) to address these objectives. As a result, the function required of the soil cover tends to be lost.…”

“…As a result, the function required of the soil cover tends to be lost. Rykaart et al (2006) identified the key mine closure objectives in relation to reactive waste rock of minimising human and animal health and safety risks, minimising environmental impacts, and maximising future land use post-mining. Possible soil cover functions for reactive waste rock should include promoting geotechnical stability, stabilising waste (i.e., against dust and erosion), minimising oxidation, minimising seepage to the environment, and promoting vegetation.…”

“…Possible soil cover functions for reactive waste rock should include promoting geotechnical stability, stabilising waste (i.e., against dust and erosion), minimising oxidation, minimising seepage to the environment, and promoting vegetation. Rykaart et al (2006) highlighted that there are essentially no standard design procedures or designs for soil covers constructed over reactive waste rock. This is in stark contrast to the minimum standards typically enforced by regulation for soil covers over hazardous, industrial and municipal landfills.…”