Sutton, MW & Weiersbye, I 2008, 'Land-Use After Mine Closure — Risk Assessment of Gold and Uranium Mine Residue Deposits on the Eastern Witwatersrand, South Africa', in AB Fourie, M Tibbett, I Weiersbye & P Dye (eds), Mine Closure 2008: Proceedings of the Third International Seminar on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 363-374, https://doi.org/10.36487/ACG_repo/852_33
(https://papers.acg.uwa.edu.au/p/852_33_Sutton/)
Abstract: Elements from gold and uranium-bearing outcrops and mine residue deposits (MRDs) on the Witwatersrand 
are transported into the surrounding environment through the action of wind and water. The concentrations 
of some consequently become enriched relative to their average crustal abundances. The aim of this study 
was to provide a gold mining company (AngloGold Ashanti Ltd.), the provincial environmental regulator 
(Gauteng Department of Agriculture, Conservation and Environment - GDACE) and the local Municipality 
(Ekurhuleni Metropolitan Municipality - EMM) with a simple decision-support tool to aid in prioritizing 
MRDs for mitigation and reaching agreement on safe and sustainable end land-uses.  
We used a numerical rating scheme for a risk assessment, which combined a number of parameters in two 
separate stages to calculate a risk index. The first stage involved the classification of hazards associated 
with MRDs while the second involved an assessment of receptor vulnerability. Selecting the EMM 
(1923 km2) as a study site, we combined historical aerial photographs (1938 to 2003) with geographical and 
multi-spectral data in a Geographical Information System (GIS). The multi-spectral data were acquired in 
2002 and 2003 by the TERRA satellite’s Advanced Spaceborne Thermal Emission and Reflection Radiometer 
(ASTER) sensor. Thematic images for five mineral signatures that we considered indicators of different 
routes of contaminant transport were derived from the ASTER data. 
We identified and classified MRDs according to type, status or footprint type, and then subjectively identified 
the hazards to land-use based on a scientific literature survey. We selected acid rock drainage and dust as 
the major hazards and then utilized the findings expressed in the literature survey to assign ratings for the 
different classes of MRDs. For the vulnerability assessment, we identified proximity of MRDs to dolomites, 
watercourses, agricultural land and dwellings as critical, based on a combination of literature review, 
historical aerial photographs (which also allowed old sidewall failures to be mapped), and remote sensing of 
the mineral signatures (indicating potential contamination of surrounding land). Based on this approach, of 
the 287 MRDs identified, we classified 50% as being of lower-risk; 40% as of medium-risk; 10% of higher 
risk and 0% as of very high risk. All 30 of the higher-risk sites were slimes dams. The results of this exercise 
can be used to support the selection of sites for quantitative risk-assessment, and to focus resources on the 
higher-risk sites for mitigation or remedial measures.