Following the recent catastrophic collapse of the Brumadinho tailings dam, the second such event to impact Brazil in three years (EA 30-Jan-19), British environmental engineering and hydraulics specialist HR Wallingford has issued a report looking at ways to minimise the risks of this type of earthen embankment dam commonly used in the mining sector.
The failure rates of tailings dams have historically been statistically higher than that of conventional water retention dams, which has driven the mining industry to step up efforts to ensure their integrity.
With significant risks particularly for populous areas downstream of these structures in the event of a failure, there are three key factors in their use, according to HR Wallingford technical director Craig Goff:
- They are often raised repeatedly throughout their lives;
- They store a mixture of water and (sometimes toxic) minerals in their reservoirs; and
- When the reservoir is ‘full’ or mining operations cease they are left in place, rather than removed.
Furthermore, when linked to mining operations that have proven to be financially unviable, it is not uncommon for these dams to be abandoned by their bankrupted mining developers, making the long-term monitoring of these orphaned structures extremely challenging, Gof adds.
As part of a consortium, HR Wallingford has been working on the use of space-data to develop a system called DAMSAT that can improve the monitoring of tailings dams. The initiative forms part of the ‘Minimising the risk of tailings dam failures through the use of remote sensing data’ project which is funded by the UK Space Agency’s International Partnership Programme. Aimed primarily at regulators responsible for monitoring many tailings sites over a large area, this system will help improve transparency within the sector. It could also provide vital extra time to deal with a potentially risky situation.
Goff explains: "We are using meteorological forecasts coupled with hydrological models to try to predict the impacts of rainfall on the reservoirs and the embankment structures. By exploiting Global Navigation Satellite System (GNSS) data with base stations, we can gather accurate movement data for key points on a structure, and by using Interferometric Synthetic-Aperture Radar (InSAR) data we can monitor movement over wide areas to give warning of landslides or slips. Optical satellite data sets will allow us to monitor indicators of pollutants that may leak from a tailings dam. All of this data will be gathered and analysed in a secure cloud-based system provided by project partner Siemens, and pre-modelled dam-breach flood scenario data can be stored here for use by emergency planners to call upon in the event of an emergency."
Also contributing to the project, which launched in April 2018 and runs until October 2020, are Telespazio VEGA, Siemens Corporate Technology, Satellite Application Catapult, Oxford Policy Management, and the Smith School of Enterprise and the Environment at Oxford University. Partners in Peru are Ciemam SAC, the National Foundation for Hydraulic Engineering (Peru), and the National University of Cajamarca: School of Hydraulic Engineering and Faculty of Engineering.