Geological surveys maintain relevance in the twenty-first century, especially in assessing and finding solutions to environmental hazards caused by unsustainable mining practices, says Council for Geoscience (CGS) specialist scientist for the Environmental Geoscience Unit Henk Coetzee.
Speaking at the CGS Centennial Celebration and Conference, held at the CGS offices in Silverton, Pretoria, this month, Coetzee noted that the role of geological surveys had changed since the CGS was formed in 1912.
“Historically, the role of geo-logical surveys was discovery, the mapping of geology and mineral resources and maintaining databases related to geology and minerals.
“Today, the role involves the generation and maintenance of spatial data regarding the geosphere and the generation of spatial data products and interpretations,” he said.
Historically, surveys were used to understand the processes at the interfaces between the lithosphere, the hydrosphere, the biosphere and the atmosphere, Coetzee noted.
He explained that, since the 1980s, a new paradigm of earth system science had developed, which also looked at the inter- actions with the anthropo- sphere – the part of the environ- ment made or modified by humans for use in human activities and habitats.
Coetzee identified research and the implementation of solutions as important aspects of a geological survey and the geoscientific responses it generated.
“Research involves identifying a problem, describing a problem and solving a problem. Research and understanding are not enough, the aim of studies and research should be to solve problems,” he said.
Coetzee used the examples of environmental impacts that stem from mining, like acid mine drainage (AMD) and radioactivity.
He noted that the duration of any environmental impact depended on the baseline situation and the ongoing environmental conditions and impact on the affected area.
Environmental impacts were manageable when adequate baseline data was available and assessments and models, which were used to develop closure and mitigation plans, were sound, Coetzee said.
“Radiometric surveys carried out between 1991 and 1993 by the CGS Geophysics Unit identified radioactive contamination of streams in the Witwatersrand goldfields.
“Following up these anomalies built the current knowledge and expertise we have in mining and the environment,” he said.
Coetzee noted the three scales of investigation used when reviewing environmental impacts – regional, local and laboratory.
Regional investigation entailed the use of satellite imagery for a large area, which allowed feature identification and interpretation on a regional and local scale.
Local investigation combined basic field measurements with more technologically advanced methods and laboratory investigation set up experiments to observe the way in which processes happened in nature.
Regional Closure Strategies
Regional closure strategies for the Witwatersrand mining areas were being developed for the Department of Mineral Resources (DMR), in partnership with the CGS, the Council for Scientific and Industrial Research and autonomous research and development organisation Mintek, Coetzee noted.
“These strategies acknowledge the underground interconnection among mines, leading to cumulative and integrated impacts on the environment and society, with multiple mines responsible for the impacts on the environment within regions,” he explained.
Coetzee noted that the key aspects of the closure strategies addressed issues like socioeconomic matters, water management, dust, radioactivity, ground instability and land sterilisation.
He added that another key aspect of the strategies was to ensure environmental protection by pumping water to lower the mine void water level and treating this water to a standard suitable for discharge or sale to a third party.
Coetzee pointed out that assigning responsibility was another important aspect of the closure strategies.
He also highlighted the importance of establishing closure and monitoring committees to ensure meaningful stakeholder interactions and to maintain technical oversight of the process.
Witwatersrand AMD Crisis
The CGS led the team of experts who advised the inter-Ministerial committee on AMD in 2011, which led to the current programme of managing the decant of AMD in the Western basin and the rising AMD levels in the Central and Eastern basins of the Witwatersrand.
“In the Western basin, water is discharged into a receiving environment, with a salt content of 4g/ℓ, bringing the salt load to 100 t/d.
“In the Central and Eastern basins, there are concerns about the rising water levels, the risk of decant in the future if the issue is not addressed as soon as possible, salination of the downstream environment and fluid-induced seismicity,” Coetzee explained.
He said the CGS’s wetland studies were aimed at turning problems into solutions, as wetlands had been identified as major pollution sinks in mining and other environments.
“Study and understanding of these wetland environments is now being exploited in the development of passive treatment systems,” Coetzee noted.
Currently, the council’s Samindaba database provides the most complete record of historical mining and mineral exploration available.
“This forms the basis for a national database of abandoned mines and past mining activities.
“The focus of the study is now shifting to increase the pace and efficacy of the rehabilitation,” he said.
The CGS focused on asbestos, coal and dangerous mine openings, as well as using geoscientific methods to investigate, prioritise and monitor the sites in question, he added.