Water Source Identification for the Verification of Ingress Points in the Witwatersrand Goldfields Using Environmental Tracers
Mello, Tebogo (1); Madzivire, Godfrey (1,2); Ligavha-Mbelengwa, Lufuno (1); Coetzee, Henk (1); Kgari, Thato (1)
1: Council for Geoscience, South Africa; 2: University of South Africa
Acid mine drainage (AMD) continues to be a crisis in the Witwatersrand Goldfields. Acid mine water continues to flow into streams, dams and groundwater sources. To address this issue, the Interministerial Committee on Acid Mine Drainage proposed several mine water management strategies. The prevention of ingress of surface water into the mine voids, inter alia, was outlined as one of the strategies. This strategy will prevent the rising of water in the mine voids, thus reducing the volume of water to be pumped and treated. For this strategy to be effective, suspected ingress areas in the Eastern, Central and Western Basins needed to be identified and verified.
A new method of identification and verification of various ingress points in the Witwatersrand Basin was implemented. This method used emerging organic contaminants (EOCs) as environmental tracers with an aim to link the water being pumped out of the mine voids at the treatment plants to the possible sources. EOCs are organic chemicals that have no known toxicological data but are suspected to be harmful. These contaminants are very persistent compounds in the environment, therefore, they are suitable tracers in the groundwater field, water source and/or pollution source determination. During the implementation of this strategy, surface water was sampled from suspected points/areas of ingress and the water being pumped from the mine voids was also collected for the analysis of the following EOCs: atrazine, metolachlor, terbuthylazine, carbamazepine and caffeine.
Three statistical analyses (cluster, correlation and trend analysis) techniques were used to evaluate the results and to establish the ingress points. In the Eastern Basin, the ingress points were found along the Blesbokspruit. One of the lakes in the Eastern Basin (Leeupan) was found to have a similar EOC signature to that of the water being pumped from the mine voids. In the Central Basin, the following were highlighted as ingress points: Wemmer Pan, Amalgam Canal site, Florida Lake and Klip River at DRD. In the Western Basin, the Blesbokspruit has water with similar EOC signature in addition to West Wits Pit, Klipriver Tributary at Mindalore and Stream at Sinqobile.
This technique is ideal for determining the link between the water sources and the receptor through the comparison of the signatures of the emerging contaminants. Once the linkage is outlined, the necessary remediation measures can be put in place to resolve the water ingress crisis.