More on slimes dams, tailings impoundments, and processed geological materials residue deposits. Here is an extract from a recent e-mail setting out the regulations that govern tailings dams in South Africa.
Mine residue deposits: Tailings dams.
- We do not differentiate, as is the USA practice, between coal and other metal deposits.
- As RSA is a small country we do not have regional, provincial or state type different legislation. We only have one national set of legislation. Of course the weather changes accorss RSA and therefore there will regionally be a different focus on, for example water management, but the same set of legislation is valids across the country.
- Mine residue deposits include all sand dumps, rock dumps, tailings dams, slimes dams (slimes in this context denotes tailings which comprise other materials other than rock flour, including clays from mineral sands, clay minerals from diamond processing and other minerals and chemical compositions) and dams in which mine residue is deposited. Effectively this is above ground, although if mine residue is placed below ground, other legislation applies such as the tailings backfilling practice and environmental and water quality legislation.
- In RSA, the first major tailings dam failure was Bafokeng in 1974. This was a platinum tailings dam with no underdrains where ,after a rainstorm, the side was overtopped, the tailings ran down a shaft and down a stream and a nine people were killed. It was a similar sized problem to the Merriespruit failure.
- The consequence of that failure was that tailings dams begun to be designed with underdrains.
- Later the Chamber of Mines compiled a set of guidelines which were used for tailings dam design.
- In 1994, the Merriespruit tailings dam failure occurred.
- In 1998, the SANS code of practice for Mine residue deposits 10286, 1998, was published; this has been the backbone of tailings dam design in RSA. This is a good document which advises all parties involved with tailings dam design, operations and closure what their responsibilities and duties of care are. It is probably fair to note that this document requires revision in a number of areas specifically with regard to closure and environmental considerations, as there has been a step-change in world practice in the last say 12 years. Risk mitigation may be another area of revision.
- In May 2001, the then Department of Minerals and Energy: Mine Health and Safety Inspectorate published a guideline for the compilation of a mandatory code of practice on mine residue deposits. In effect this document focuses on the required reports for mine residue deposits and the updating thereof.
- In effect until 1998, there was no requirement to produce a tailings dam design report. Furthermore until 2001, Mines were not obliged to always document design, construction and operating aspects. From 2001, in effect, the documentation for mine residue deposits should be in place. There are still some mines and some mine residue deposits for which the relevant documentation is still being prepared, but this is an ongoing process to cater for the backlog as well as some of the mines have been in operation for more than 50 years.
- Irrespective of the chemical nature of the mine residue deposits, if the mine residue deposit is in a solid form and/or comprise solid particles, then this area of best practice would apply as presented above. For all dams containing liquor/liquid phase material the water dam legislation will apply to water dams, pollution control and liquor dams.
The Environmental, OSH acts also refer as well as specific implications of other sections of the Mines acts.
In order to classify the geochemistry of the tailings you need to consider the Minimum Requirements Guidelines of the Department of Water Affairs which is referenced in the MPRDA acts. You will need to consider the Environmental legislation which also covers other waste products.
Water dams and pollution control dams:
- In RSA, the National Water Act 36 of 1998 refers. It was also amended in 1999 by National Water Amendment Act 45. In 2010 it is likely that further amendments will be made with regard to the dam safety legislation. In the recent Sancold conference October 2010, there were some presentations on what will be included in the revised dam safety legislation.
- Based on the ICOLD experience, in RSA in 1986 the first dam safety legislation was promulgated and has been used until now. All dams containing water or liquor are classified in terms of three classes, I, II and III, following the international practice in this regard.
- The size of supernatant pool on a tailings dam will also require classification in terms of these three classes. Therefore there are two sets of legislation which directly affects tailings dams, the management of the tailings and the management of water on the tailings dam.
- In the past, Mines were outside of the jurisdiction of the National Water Act, specifically related to Liquor dams. However, the normal practice was to ensure that the best practice was applied where required, so that in the event something goes wrong one is then not prosecuted on a civil basis.
- In recent years since 1998, mines have to apply for a water use license. This means that for them to operate, if they require to use any water, they have to comply with the National Water Act.
You will see from the above discussion that there has been development with time and as always different Government departments have different mandates. For example there are moves afoot to have mine authorization from the Environmental Department and not any longer from the Minerals Department: this will complicate matters.
Hope this helps and provides some guidance.
PS: Here is more from somebody who knows more and has a better memory than me:
- Bafokeng was not the first major TSF failure. There were many before that including Simmer & Jack in the 1930’s (I think) that took out a train and killed the driver and fireman.
- Underdrains started in the 1950’s after a failure at St Helena. It was the study carried out by George Donaldson (under Jennings) that looked at the most effective layout of these drains. Up to then a Herringbone drain layout had been used, to be replaced by toe and internal ring drains.
- The Chamber of Mines had a guideline out many years ago. This aligns with what we have in Australia, which is a series of State published guidelines, not regulations. Need to check on what the CoM guidelines said about design reports.