By Jack Caldwell - Mining Engineer - Robertson GeoConsultants

Browsing through the proceedings of the 1998 conference on Tailings and Mine Waste I came across three papers on the failure of the Merrispruit Tailings Impoundment. At this remove of time it is still instructive to reread these old papers and ponder the lessons learnt. Here is a paragraph from the conclusions of one of the papers:

Following the inquest/enquiry into the disaster, Judge Kotze found that “it is clear beyond all doubt that the tailings dam system, which was operated by people chosen by the mining company and the tailings dam company, did not function with any measure of safety. In passing it can be mentioned that the practice of the Department of Mines and Energy to appoint old mine captain, without training, as inspectors is definitely not satisfactory.”

There follows this indictment of the system, which supports our contention that many things have to go wrong for a system to fail:

The management structures withinthe industry were poor, as exemplified by the lackof proper contract documents andhence the lack of clarity on who was responsible for what. There was poor communication within the organizations, possibly aggravated by the lack of relevant technical knowledge by those charged with responsibilities beyond their expertise. This meant there was lack of adequate documentation or records on which any proper monitoring of problems or progress towards their solution could be based. Those placed in positions of authority had not received training in the fields of expertise required–largely the engineering performance of materials comprising tailings dams or the implications of environmental conditions. In fact, there seems to have been a dearth of the practical engineering skills required, instead of mining, electrical or mechanical experience.

Two accompanying papers tell of the remediation of the dam after its failure and of planned long-term continued use of the facility in the longer term. This is a magnificent set of papers—if only these days similar high-quality papers about large failures were published. But this is unlikely as the admissions of failures, multiple failures,contained in these papers could only occur in the light of open court enquiry; no mine, no consulting company on their own, would every permit publication in the absence of the findings of a judge and court. As noted in the paper:

Consequently it was established beyond doubt that overtopping, as a resultof inadequate freeboard, was the primary cause of the failure. While there was initially some indirect evidence pointing to this having been the case, it was only irrefutable proved after the satellite imagery had become available and subsequent confession by individuals who had been aware of the actual situation at the time. It is alarming to think that had such key evidence not been available, the true cause of the failure may still be shrouded in uncertainty.