ABSTRACT: Water tracer technologies can help optimise water management in coal mining operations and improve outcomes from environmental studies and controls to protect sensitive assets. ACARP project C28024 (Stage 1) is demonstrating how tracer analysis of groundwater and surface water can provide information on whether systems are hydrologically disconnected, partly connected or well connected. This stage of the project is focusing on conventional tracers that are often used by other mining industries around the world (e.g. iron ore, potash) and in groundwater resource studies. Stage 2 of this project proposes to test new artificial tracers combined with suitable conventional tracers that are particularly useful for identifying seepage sources for control actions.
This paper will demonstrate and discuss the benefits and limitations of major groups of conventional tracers that are commonly measured naturally in water. These include: field parameters (e.g. electrical conductivity, temperature), major and trace ions (e.g. metals), stable isotopes of oxygen and hydrogen, industrial compounds (CFCs and SF6) and dissolved carbon isotopes (i.e. inorganic and organic forms). In addition, this paper will discuss radioisotope tracers (e.g. tritium, carbon-14 and radon-222), as robust and proven tools to help differentiate shallow and deep groundwater where there is a contrast in water residence time (groundwater ‘age’). These tracers can provide useful information on seepage, despite higher analysis costs and turn-around times for laboratory results.
Key findings from demonstration mine sites show the importance of combining physical water measurements (e.g. water levels and pumping rates) with a suitable combination of water tracers, depending on the site specific issues or study questions. For example, artificial tracers that are added to water sources are most suitable for identifying seepage and rapid flow pathways that can be a risk to underground operations. However, common artificial tracers such as added salts and dye tracers can also raise community concerns, such as producing flourescent green creeks. Novel artificial tracers are able to overcome these risks. For example, synthetic DNA with uniquely designed fingerprints can be released at different times and locations to identify the sources of water to excavations can then be controlled.
Commensurate with the risks of the project, a combination of suitable tracer technologies of different types can increase the confidence in identifiying water sources and flow rates underground. However, the costs, limitations and practical challenges of each proposed tracer should be considered in planning tracer studies. The outcomes of these ACARP projects will assist coal mining operators in deciding on the suitable combinations of tracers for different types of operational and environmental risks associated with underground mining, and show how tracer technologies can be used to check possible flow paths in conceptual and numerical models.