Hydrogeological study of the Glencoe Corobrik Factory Site, KwaZulu-Natal Province, South Africa
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Date
2021
Authors
Moabelo, Maserole Elvis
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Abstract
Hydrogeological conditions at the Glencoe Corobrik Factory, KwaZulu-Natal, South Africa, are
investigated in this study. The general geology of the area is made up of the Ecca Group
metasedimentary sequence of the Karoo Supergroup. A hydrogeological conceptual site model is
developed based on the data acquired during the study. The methods of data collection involved
borehole drilling and logging, aquifer tests, water sampling and analyses. Aquifer tests were
conducted using a slug test method on two newly drilled boreholes for this research. The calculated
hydraulic conductivity and transmissivity values are 0.014 m/day and 0.033 m/day, 0.44 m2
/day
and 1.19 m2
/day for BH01 and BH02, respectively. The underlying rocks are sandstones and
siltstones of the Vryhied Formation that constitute the main lithology for the aquifer in the area.
Dolerite dykes may be interfingered with the sandstones at depth, creating a flow barrier and
conduit in some places. The weathered aquifer is made up of the upper sequence sandstones, while
the dolerite emplacement presents a secondary fractured aquifer. Groundwater chemistry is
dominated by two water types; Ca2+
- HCO3
-
and Na+
- HCO3
-
. The Durov diagram points to ion
exchange processes where Ca2+ is exchanged for Na+
. The groundwater chemistry is influenced
by weathering processes (silicates). The study revealed human activities have a low influence on
the groundwater chemistry in the area. The Ca2+ and Mg2+ vs SO4
2-
plots provided crucial evidence
that the groundwater has not been influenced by acid mine drainage even though the area was
previously dominated by coal mining activity. Surface water chemistry is represented by Ca2+
-
HCO3
- water type with Mg2+
- SO4
2-
and Na+
- HCO3
-
also occurring as minor water types. Most
samples are clustered towards the region of Mg2+
- SO4
2-
, indicating a possible influence of
sulphates that may be derived from the old mine dumps on the surface. Based on the current
hydrochemical data, groundwater and surface water have distinct geochemical compositions,
which implies that contaminants emanated from surface processes have less influence on the deep
groundwater system. Results from the stable isotopes also support the hydrochemical results
suggesting a very minimal link between the groundwater and surface water based on the current
sampling. Groundwater samples were recharged directly from rainfall prior to evaporation, while
surface water samples show an evaporation effect. Surface water samples showed an evaporation
effect with an evaporation equation of δD = 4.31 δ18O+7‰ with a R
2
value of 0.98.
Description
A research report submitted in fulfilment of the requirements for the degree Masters of Science in Hydrogeology to the Faculty of Science, School of Geosciences, University of the Witwatersrand, Johannesburg, 2021