Abstract
M.Sc.
The decommissioning of mines and mining-related activities brings about the onset of
rehabilitation. A legacy that most coal mines must address is the rehabilitation of the coal
discard dumps that are generated by the beneficiation process of the raw coal. Rehabilitation
involves the shaping and covering with a topsoil layer of these coal discard dumps. The
topsoil layer is then revegetated to provide a stable form of protection against erosion.
Considerations taken into account regarding the rehabilitation of coal discard dumps include
the final slope angle, physical constraints i.e. railways or rivers, a source of topsoil and the
grass species to be sown. Once the dump has been shaped, capped and seeded, regular
applications of fertilizer take place for a defined period of time. This is to accelerate the
growth of the grasses, as well as to stabilise the nutrient levels in the topsoil capping.
Ingwe Mine Closure Operations (MCO), part of Ingwe Collieries Limited, is the business unit
entrusted with the management and successful rehabilitation of Ingwe’s defunct operations.
All of the coal discard dumps sampled in this study are found on such defunct operations.
These coal discard dumps have been rehabilitated to a very high standard by MCO, and in
most cases exceed the minimum requirements stipulated by law and guideline documents.
This study and the results obtained from it reflect this.
This study investigated, in terms of defined types of cover, whether or not there is a
statistically significant difference between the:
• six coal discard dumps from which data were collected;
• five different defined slope aspects;
• two groups of slope angles; and
• slope angle and slope aspect in terms of cover.
The data collected was analysed statistically, so as to determine whether significant
differences (95 percentile confidence level), in terms of cover, exist. The purpose of this was
to determine whether or not a preferred slope aspect or slope angle group could be identified
for the six coal discard dumps sampled. By identifying a preferred slope aspect or slope angle
group, companies could alter the design of operational or defunct dumps so as to maximise
these. This would make the rehabilitation of the dump more sustainable and could possibly
reduce aftercare costs.
Through statistical analysis of the data collected it was determined that:
• of the six coal discard dumps sampled, significant differences did exist between some of
the dumps regarding basal cover, plant litter cover and bare ground. As each dump is
different with its own specific micro-climate, this can be expected. The age of the dumps
could also have played a role in terms of development;
• of the five different defined slope aspects analysed, no significant differences existed
between any of them;
• of the two groups of slope angles analysed, no significant difference existed between
them; and
• no relationship between slope angle and slope aspect, in terms of cover, could be
established.
The analysis of the data collected was done by means of ANOVA one-way tests, coupled
with Post Hoc Tests and Contrast Tables. The results of the statistical analysis were evaluated
by the STATCON Department of the Rand Afrikaans University for accuracy. The data and
the statistical analysis thereof were found to be satisfactory and correct.
Various other statistical analyses were conducted on the data, but the results obtained from
these tests were all the same as that of the original data analysis. These analyses included the
Univariate Analysis of Variance, T-tests and Mann-Whitney tests.