Mine waste monitoring information includes:
• Delineation of extent and topographic structure of the waste structures
• Status of water discharges from tailings structures
• Characterisation of water movement through tailings structures
• Vegetation stress and soil status in areas adjacent to tailings structures
• Slope stability over tailings structures
• Stability of tailing retaining walls
Spatial resolution of the majority of analysis maps is at least 1 m. Slope stability is for individual slope units with boundaries delineated with a location accuracy of approximately 1m. Stability of tailings retaining walls is measured using using the precision land motion service and the separation between measurement points will depend on the structure of the retaining wall. Typically at least one measurement point each 10 m is expected when high resolution radar imagery is used and one measurement point each 50 m when systems such as ENVISAT are used. Analysis is usually conducted every few months and it is possible for EO based services to support this update frequency for most areas unless they are subject to very heavy cloud cover. Stability of retaining walls is monitored every few weeks.

Structure of the tailings pile combined with a Digital Elevation Model for the area around the tailings piles. The most recent height contours for the tailings piles are overlaid on the DEM. CREDITS: Effigis Geosolutions

An assessment of mine tailings– green areas illustrate stable waste, blue areas illustrate ponds and red areas indicate areas of potential instability to be monitored – the arrows indicate the direction of water flow through and over the tailings piles.

Location accuracy is better than 1 pixel assuming effective correction of the satellite imagery. The accuracy of contaminant detection depends on the material. Many of the by-products from gold mining contain complexes with distinct optical properties. Their detection is therefore quite straightforward. Detection of vegetation stress depends on the nature of the stress. Often chemical contamination leaching into the soil or water table is detectable after low levels of exposure. Slope stability characterisation is currently undergoing validation as the number of test cases remains limited at present. Stability of tailing retaining structures is a similar analysis to geotechnical risk assessment and land motion.
Monitoring the extent of mine tailings as well as the evolution of slopes and movement of water within the tailings pile ensure that the risk of contamination to surrounding habitats can be
minimised In particular, routine monitoring can help prevent the catastrophic failure of tailings retaining structures observed in Hungary in 2010 and Baia Mare, Romania in 2000.
Sentinel-1 will support greater medium resolution (i.e. 20 m) monitoring of retaining wall stability. Most of the other products depend primarily on high resolution optical or radar imagery.