Critical Geotechnical Factors Impacting on Reserves in Previously Mined Areas in the Northern Witbank-highveld Coalfield

Sustainability in mining is still framed in neoclassical economic terms, measured by profit, shareholder value and growth, with social and environmental dimensions added in response to regulation. Six air quality and waste minimisation projects run over seven years were assessed against seven dimensions of the biosphere and fell well short. A collaborative model is proposed for a sector built on mining waste residues.

Stockpiling degraded every soil property measured across four Witbank area mines. Clay content of topsoil and subsoil rose by 50 to 60 per cent, surface bulk density increased from stockpiling through to rehabilitation, and effective depth on rehabilitated areas was under 17 cm in most cases. Topsoil organic carbon fell by almost half and microbial species numbers dropped in the stockpiles.