Written by Shane Teek & Dr Charles MacRobert  

A tailings storage facility (TSF) at Jagersfontein failed between approximately 6 AM on Sunday 11 September 2022 causing an environmental catastrophe that is still unfolding. The dam burst, flooding the town and causing families to lose their homes, numerous hospitalisations and significant loss of life.

Images of the flooding at the Jagersfontein dam

Photo credits: https://disasterscharter.org/web/guest/activations/-/article/flood-large-in-south-africa-activation-776- 

How could this event have occurred?

When commencing with any project, particularly projects with potentially significant environmental consequences such as a mining operation, baseline and scoping assessments are required by law (NEMA). 

Often such baseline assessments include appraisals conducted by specialists to provide data and interpretations on the environmental standing of the area that has been proposed for development. 

Such specialists include botanists, to ensure no endangered flora exist within the area around the development footprint; hydrogeologists to determine the conditions of the groundwater in the region prior to commencement of development and activities on-site, and geotechnical specialists to investigate the status of ground conditions at the site of development and characterise the material properties to be used in engineering design of the facility, to name a few. 

Very often, continued monitoring of environmental conditions, including hydrogeological and geotechnical conditions, is a recommended mitigation measure within the findings of such baseline and scoping assessments.

Monitoring might include the following:

Hydrogeological monitoring of boreholes on and surrounding the mine:

• Quarterly monitoring of basic groundwater parameters. 
• Examples include monitoring of water levels, electrical conductivity (EC) and pH. This monitoring can be done by automatic loggers or manually.
• Quarterly groundwater sampling for relevant screening values depending on tailings composition and the by-products used to liberate the valuable minerals from the host rock.
• Quarterly and annual comparison of collected data to baseline conditions.

Geotechnical monitoring of:

• Water levels within mine tailings dam, similarly this could be done using automatic loggers or manually.
• Extensometers and inclinometers are helpful for assessing movements within the tailings dam.
• Geo-resistivity monitors can show localised or preferential seepage within a tailings dam.
• Remote sensing includes InSAR which measures ground deformation by satellite.

The need for monitoring

The importance and value of monitoring geotechnical and groundwater conditions in mining operations cannot be overstated. Careful monitoring can prevent dam failures and the devastating human and environmental consequences arising from such failures.

SABC reports on the mine dam bursting incident

References:

https://www.dffe.gov.za/legislation/actsregulations