Earth observation data and satellite InSAR for the remote monitoring of tailings storage facilities: a case study of Cadia Mine, Australia

Abstract

Tailings storage facilities (TSFs) are an essential infrastructure of mineral processing, but they represent a significant physical, chemical and biological hazard and must, therefore, be strictly and responsibly sited, managed and closed. Tailings can, for example, be dispersed by many processes (such as sinkholes, earthquakes, intense rainfall and flood events, and wind), substandard design and construction, and seepage. The stability and behaviour of TSFs needs to be continuously monitored and one highly effective way of doing this is through satellite Earth observation (EO). The EO industry is witnessing a technological revolution. Large and long-lifespan satellite sensors that have been the staple of national space agencies and commercial satellite manufacturers are now being complemented by constellations of low-cost, short-lifespan 'cube sats' by companies with the ambition to image the whole earth daily. Satellites with synthetic aperture radar (SAR) sensors are also collecting high volumes of data, with the added benefit of being able to do so day or night and in different weather conditions. The range of data options and capabilities these provide open opportunities for novel data analysis techniques for TSFs. One of these is satellite InSAR (interferometric SAR; a technique used to map millimetric-precision changes in ground height over time), which is already used by mining companies to reduce risk in and of their operations. From monitoring the stability of TSFs, through to assessments of impacts of natural hazards, InSAR allows rapid and accurate targeting of high-risk areas and structures to identify those that require subsequent investigation through ground-based methods. To demonstrate the application of EO data and InSAR in identifying pre-and post-failure mine activities and TSF deformation, the authors will present a case study across Cadia mine, New South Wales, Australia, which had a localised TSF failure on 9 March 2018. The InSAR results presented show that low-magnitude subsidence signals were observed across the TSF dam during the year preceding the collapse. In January 2018 a notable change in behaviour was observed, with a concentrated area of subsidence focused on the region which initially failed on 9 March 2018. Furthermore, post-collapse InSAR measurements show an increased rate of subsidence for regions either side of the failure zone. Review of medium-and high-resolution satellite images show that the failure was phased, with an initial failure and then a subsequent failure at least two days after 9 March 2018. It also highlights what might be construction activity associated with a dam raise prior to failure.

Guidelines and recommendations on minimum factors of safety for slope stability of tailings dams

“…For example, usually the displacement measurements refer only to a given orientation axis or plane related to the line of sight of the equipment, potentially implying a bias. Also, authors state that changes in surface conditions -for example, moisture, temperature, and especially vegetation -may lead to significant noise and errors in measurements (Thomas et al, 2019;Robertson, et al, 2019, Gama, et al, 2013.…”

DAMSAT: An Eye in the Sky for Monitoring Tailings Dams

“…This poses a difficult challenge to significantly reducing tailings dam failures; hence, there is an acute need to monitor junior mining operations (Lumbroso et al 2019). Recent work has shown that a low-cost tool, which uses EO-based information, could help improve the capacity of environmental regulators and non-governmental organisations (NGOs) to monitor tailings by improving their oversight of both large and small mines (Chetty 2013;Hui et al 2015;Thomas et al 2019).…”

Combining Satellite InSAR, Slope Units and Finite Element Modeling for Stability Analysis in Mining Waste Disposal Areas

“…In particular, case studies on the use of satellite InSAR to analyze mining-induced slope instabilities are scarce, as most of them focus on ground subsidence (e.g., [16][17][18]). Nevertheless, the application of such technique has been documented in a few mining sites in Australia [19,20], Brazil [21,22], Spain [23,24], South Africa [15], Turkey [7], and U.S.A. [14,25]. However, in most cases these works present analyses of the InSAR data at the slope scale, or include no complementary stability analyses taking into account geotechnical data through geo-mechanical modeling.…”