Abandoned mines and their associated hazards can pose major threats to local communities and the environment. This worldwide problem is the result of the extraordinary mining development that took place in specific areas in the late 19th and early 20th centuries.
Whereas active mining operations are mostly well monitored, the approach when the mine is no longer profitable and is abandoned can vary from country to country. Following the closure of a mine, the awareness of previous mining activities often decreases but former mine shafts and underground cavities, re-filled open pits, tailings and dumping sites still exist.
Hazards requiring mitigation can include collapses migrating to the ground surface: sinkholes, slope instabilities and collapses, subsidence or uplift of the ground surface, and alteration of groundwater quality and quantity.
Most mining authorities have similar information needs. The common steps to evaluating the risk are: mapping and assessing the hazard, identifying the exposure of people and infrastructure, and monitoring the hazard with a frequency dependent on the magnitude of the hazard and the risk posed.
The good news is that accurate technology tools exist that can make a difference to support this risk mitigation cycle. Satellite technology in particular can make a meaningful contribution to quantifying and evaluating the global inactive mine hazard.
In the last decade, our mining clients have identified the following main benefits of using InSAR technology for controlling inactive mines:
- our InSAR studies provide a picture of ground movement on a wide scale: covering larger areas than is possible by conventional surveying techniques,
- our results help identify and prioritise which areas need to be monitored or investigated with instrumentation,
- the combination of InSAR data with other data sources allows for the improvement of predictive ground motion models.
A recent example of the use of InSAR for abandoned mines is the monitoring of ground deformation on the area of salt mines of Solotvyno, Ukraine. This project is within the framework of the Copernicus Emergency Management Service, under an activation launched by the National Directorate for Disaster Management, Hungary.
Together with our partners Geoapikonisis SA, National Observatory of Athens and CIMA Foundation, we studied the ground motion dynamics of the area from 1997 to 2016, using data from Sentinel-1, ERS and ENVISAT satellites. A derived sinkhole and landslide risk map has been produced for the area studied. All maps can be accessed at the European Commission Copernicus website.
Another example of satellite monitoring for the analysis of areas where mine subsidence is an important constraint on urban planning, and requires evaluation of the historical trend of the phenomena is the success story of the Ville de Dax, in France.
Besides the different legal regulations within each country, in recent years environmental scientists, hydrogeologists and mining engineers are bringing their expertise to aid in the characterising and monitoring of these sites. In this context, InSAR technology provides countless opportunities for a better addressed sustainable management of abandoned mines.