Merriespruit tailings dam disaster

The nearest houses were located 300 m downslope of the dam; when the wave of water and tailings reached them, it was 2.5 m high.

[2] When gold-bearing rock is processed and the gold is extracted, the remaining material is moved to tailings dams as waste, as was the case at the Merriespruit No.

[2] In the early years the slurry had a low relative density that led to difficult construction conditions with seepage and sloughing on the northern wall.

[1] Piezometers were installed and the water table established; the contractor calculated the stability factor of safety to be 1.34[1] The No 4 dam was in an unacceptable condition prior to failure.

Contrary to legislative requirements, at the time of failure the dam did not have the capacity to maintain a 0.5-m freeboard during a one-in-100-year 24-hour storm.

[3] An eyewitness reported a strong stream of water entering the town downstream of the dam at 7:00 pm on the evening of the disaster, which was not the first time such a phenomenon had occurred.

The State conducted investigations including looking at eyewitness accounts, weather and hydrological data, laboratory and in situ tailings testing, satellite imagery, and overtopping studies using a scale model.

[2] The South African government appointed the Council for Scientific and Industrial Research to investigate, which confirmed the conclusions reached; as a result the 1995 Draft Code of Practice for the Design, Operation, and Closure of Tailings Dams was introduced.