Oral Presentation Australasian Groundwater Conference 2017

Use of control charts for groundwater quality monitoring and assessment – the Queensland (Australia) experience (#26)

John Broughton 1 , Tim Anderson 1
  1. NRA Environmental Consultants, CAIRNS, QLD, Australia

The purpose of monitoring is to detect impacts associated with the monitored activity. Where an impact occurs, monitoring should provide early detection, thus allowing for early corrective action. Groundwater quality monitoring programs developed for compliance assessment as part of mining licencing requirements in Queensland are rarely this useful. Problems such as poor data collection and insufficient quality control can be easily remedied. More significant issues are the representativeness of compared bores used by inter-bore monitoring approaches and the high false-positive rate of the compliance assessment. A control chart monitoring approach that addresses these issues is presented here.                                                      

This presentation describes the adaptation of existing control chart groundwater quality monitoring approaches to meet the environment management and regulatory requirements of mining operations in Queensland. The adapted approach has been operational at a major Queensland mine for two years and has proven effective in detecting situations requiring management intervention and in reducing false-positives that would otherwise be generated by traditional approaches.

The approach has two key advantages. Firstly, it uses an intra-bore data comparison, rather than comparing data from ‘compliance’ and ‘reference’ bores, negating the issue of representativeness. Secondly, compliance assessment for the approach uses the frequency and magnitude of monitoring values to define events, rather than just single values. This reduces false-positives. A further innovation is the use of percentiles to set control limits.

In parallel with development of the technical aspects, the regulatory context for the use of control charts in licences was negotiated with the State. The licence conditions combined detection of groundwater quality changes and protection of environmental values into an outcome that was acceptable to the mining operation and the regulator.

If suitability applied, the approach has the potential to increase the effectiveness of groundwater quality monitoring and improve regulatory and environmental outcomes at mining operations.  

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