The Dialogue has analysed water samples across the Upper Hunter to determine if any impacts to water quality arise from mining in the region.
The Upper Hunter Mining Dialogue has been testing river and mine storage water quality in multiple locations in the Upper Hunter as part of the Hunter River Water Quality (HRSTS) Assessment.
The Dialogue has undertaken this project to address concerns raised by members of the former Joint Water Working Group about the overall water quality of the Hunter River, and clarify what other elements may be present in the water discharged by mining operations.
The Hunter River Salinity Trading Scheme allows mines and other industries to discharge saline water into the Hunter River at times of high flow, which dilutes the saline water. Many of the region’s mining companies and power stations participate in the scheme.
The Dialogue established and funded the project in 2017, and worked with the University of Newcastle’s International Centre for Balanced Land Use (UoN) on the initial phase of the project. The NSW Environment Protection Authority (EPA) endorsed the project and was engaged in consultation throughout the design and initial sampling stages.
Through analysis of water and sediment samples from mine water storage sites as well as from the Hunter River, the project assessed the potential for contamination of water quality from coal mines and power utility facilities operating in the Upper Hunter. Because of the wide range of mining operators involved in the Dialogue, the study allowed a wide sampling of water quality across the Upper Hunter.
The first phase of the project resulted in a report from UoN in early 2018. This report found that few metals and metalloids exceeded the ANZECC guideline trigger values for both discharge dams and Hunter River relevant reference sites, and that overall the HRSTS scheme was performing well. However, the samples recorded elevated levels of nitrates in the storage dams (discharge points) of a number of operations.
The project steering committee met with the EPA and UoN and agreed that it was important to close out all the issues identified in the initial study before publishing the findings. Given the initial sampling was undertaken during a prolonged dry period, the committee agreed that the results were not representative of discharge conditions and had impacted the results.
The Dialogue Secretariat sought advice from Hydro Engineering and Consulting (HEC) on a monitoring protocol to examine the actual discharge levels under regular discharge conditions. This protocol was provided to member companies to enact when a discharge event occurs. Following the significant rainfall events and discharge opportunities experienced in February 2020, the Dialogue sourced data from companies to examine the results of nitrate levels under normal discharge conditions.
HEC has now completed this second phase of the project, and provided an assessment to NSWMC addressing the issues identified in the 2018 report. The assessment was able to confirm that following a period of high rainfall, lower concentrations of nitrate were detected in mine site storage dams than those recorded in the Hunter River. This confirms the relationship between nitrate concentrations and preceding rainfall, and confirms that during licenced discharges (which occur typically following periods of higher rainfall), it is likely that nitrate values would be lower than they would be following periods of low rainfall (when discharge is unlikely).
For more information on the Dialogue’s Hunter River Water Quality project and to read these reports and analysis, please click on the resources provided below.