Preliminary screening surveys of radioactivity in water sources was carried out by the Institute for Water Quality Studies in 1995 and 1996 [1,2]. The levels of the radioactive elements uranium and radium, found in streams in the vicinity of gold mining activities, were found to be elevated such that, in some cases, these streams might be regarded as unsuitable for continuous lifetime use as drinking water. Many radionuclides had not been measured, and there was no information on the variability of the radionuclide concentrations in the water sources. Due to the lack of detailed and definitive data on radionuclide concentrations, it was not possible to determine the safety or otherwise of the water sources when used for drinking water purposes without a more thorough and intensive monitoring programme. In order to obtain certain knowledge on the radiological status of the water sources to establish human health risk, it was essential that a more detailed investigation be conducted. This report summarizes the findings of an intensive radiological monitoring programme that was conducted in the Mooi River catchment during 1997.
The aims of the radioactivity monitoring programme were:
To measure and report on the most important radioactive components in surface streams and in groundwater at selected sampling locations, at regular intervals over a hydrological year.
To establish the radiation dose from untreated water for the purposes of use as drinking water, the emphasis being placed on the dissolved component of the radionuclides present in the water samples, and not on the suspended component.
To estimate, from such measurements, the incremental radiation doses above estimated background that could be received by users of the water.
To establish, on the basis of international practice, guidelines for interpreting the significance of these incremental radiation doses with a view to identifying the need for remedial action at any particular location. The recommendations would be brought to the attention of the relevant authorities within DWAF.
For clarity it is important to note what the study aims did not address. The study focussed on the radioactivity status of raw water, filtered before analysis. Some preliminary work was done on the suspended solids. All the possible uptake routes were investigated in detail, of which only the drinking water route and possibly the fish consumption route were found to be significant. Sediments, dissolved radon gas and airborne gas and dust were outside the scope of the study.
The strategy adopted to achieve the aims comprised the following:
To focus on one catchment at a time, in order of priority - the Mooi River catchment (also known as and also containing the Wonderfonteinspruit catchment) was selected as the first catchment to be studied, and forms the basis of this report.
To undertake the monitoring programme in a coordinated, transparent manner with the participation of relevant governmental and non-governmental stakeholders.
The IWQS was responsible for the management and coordination of the radioactivity monitoring programme in the Mooi River catchment. The establishment of a Coordinating Committee and Technical Committee, involving representation from a wide spectrum of organizations interested or involved in monitoring of radioactivity, assured transparency and the involvement of a range of scientific opinion and decision making on the issue. The Coordinating Committee consisted of numerous individuals and role players including Rand Water, Goldfields Water, the Western Transvaal Water Company, the Lower Wonderfonteinspruit Catchment Forum, Anglogold Limited, Gold Fields of South Africa and other representative mining companies such as Randfontein Estates, the School of Chemical Engineering of the University of Potchefstroom, the Directorate: Water Quality Management and the Gauteng Regional Office of DWAF, the Council for Nuclear Safety (CNS), the Atomic Energy Corporation (AEC), the Chamber of Mines, the Council for Geoscience and the Department of Minerals and Energy.
The Technical Committee included representation from the AEC, the Chamber of Mines, the Gauteng Regional Office, the Council for Geoscience, the Council for Nuclear Safety, and the IWQS.