This is an extract from the submission presented by Counsel Robert White to the Independent Planning Commission panel for the NW Alliance on Thursday 23 July 2020.
Environmental issues: Groundwater
CSG is natural gas found in coal seams at depths of approximately 300 to 1000 metres underground. The CSG is trapped underground by water pressure. To extract the CSG, a well is drilled into the coal seam and the water is pumped out to release the gas. The water – known as ‘produced water’ – is then separated from the gas at the surface. The produced water is highly saline. The quantities of produced water can be very large. Coal seams are less permeable than conventional gas systems and the gas does not flow as easily, which means that more wells are required to develop a CSG field than a conventional gas field.
The wells are drilled deep underground through different geological layers including groundwater formations. Groundwater – water that is located under the ground – is stored in porous soils and rocks. These saturated soils and rocks are called aquifers and the top of the saturated portion of ground constitutes the water table. Groundwater is a valuable source of water in the Pilliga, as it is used primarily for irrigation, cattle and stock farming, as well as for domestic purposes.
The target coal seams for the Project are underneath aquifers that supply important sources of water for agriculture and domestic use and are important recharge zones for the Great Artesian Basin. The extraction of gas depressurizes gas bearing ecological formations and may cause groundwater levels to decline which can impact on water users.
NWA and its members will adduce evidence from Associate Professor Matthew Currell from RMIT that the DPIE’s assessment that the project ‘would not result in any significant impacts on people or the environment’, is far from having been demonstrated and is not supported by the available evidence. There remain important uncertainties and knowledge gaps in relation to groundwater risks. Important relevant information and data continues to be lacking or has not been considered – including recently published peer reviewed research with significant findings regarding inter-aquifer connectivity.
In its assessment report, the Department has adopted an approach that such issues can be dealt with after the Project approval. Such an approach is inconsistent with the precautionary principle.
Contamination of groundwater and surface water are major environmental risks that require careful management in any unconventional gas operation, including the extraction of gas from coal seams (Hamawand et al, 2013; Vengosh et al, 2014; Vidic et al, 2013; Jackson et al, 2014). The major pathways by which contamination of groundwater can take place are:
a. contamination by wastewater (produced water) that is spilled, leaked or inappropriately managed as it is brought to the surface and subsequently stored, treated and transported;
b. contamination due to well integrity failures, or legacy/abandoned boreholes, which allow gas and/or fluids to escape from gas reservoirs and cross-contaminate other aquifers.
For the Narrabri Gas Project, the major potential contamination source is ‘produced water’ that is pumped from the coal seams in order to depressurize the seams and allow gas to de-sorb and flow freely (via the gas wells) to the surface. CSG produced water typically exhibits poor quality, due to its extended period of residence within coals. Contaminants that are characteristic of CSG produced water include high levels of sodium, heavy metals and other trace elements, such as barium and boron.
The risks associated with potential groundwater and/or surface water contamination with produced CSG water are of particular significance in the Project (in comparison with other gas projects), due to:
a. the unusually poor water quality associated with the Gunnedah Basin coal seams underneath the Project area, and
b. the unusually high quality of the shallow groundwater and surface water in the Project area, which covers areas of potential recharge for the Pilliga sandstone – one of the main aquifers in the southern Great Artesian Basin, as well as the importance of water in the Namoi Alluvium (which also occurs within or close to the Project area) to local water users.
The evidence will demonstrate that the information provided in the environmental assessment and the Department’s assessment report relating to assessment and management of groundwater and surface water contamination lacks detail and /or critical supporting data commensurate with the significance of the risks and the potentially impacted receptors.
Gas will be extracted from up to 850 wells drilled throughout the life of the Project. It is estimated that approximately 37.5 billion litres (GL) of water (up to 80 GL) will be produced from the target coal seams via these wells during the life of the Project, or approximately 1.5 GL per year. Whilst it is documented in the environmental assessment that this water is saline, the quoted salinity value in the environmental assessment is lower than previously published estimates of the produced waters from coal seams in the Project area. These salinity levels are significantly higher than typical CSG production water. As documented in a 2014 report to the Office of the Chief Scientist and Engineer, in addition to having high salinity, the water produced from the coal seams in the Narrabri region also contains significant level of heavy metals, boron and fluoride, which could make the produced water an environmental and human health hazard, and a major potential source of groundwater and surface water contamination in the area.
Produced water will be generated at all CSG wells drilled for the Project. The environmental assessment states that the produced water pumped from the target coal seams is planned to be managed through a network of water gathering lines and infield balance tanks. This water treatment system, whereby waste water from each CSG is transported to water treatment facilities, means that there will be hundreds of potential sites of contamination. Any spills or links of produced water that occur on route to or during storage at the water treatment facilities, could potentially detrimentally affect the surrounding land and shallow ground water in the uppermost unconfined water table aquifers.
The proponent has also failed to demonstrate how it will dispose of waste brine arising from the water treatment process leading to significant uncertainty about the environmental impacts of this disposal process. Independent expert evidence to be adduced by NWA and its members from Dr Stuart Khan show that there is a significant risk of low term environmental harm arising from this waste material.
Based on international experience with unconventional gas, the size of the project and the number of wells and required infrastructure to collect, transport and store the produced water, there is a strong likelihood that leaks and/or spills of produced water will occur throughout the life of the project, risking contamination of shallow aquifers and surface water bodies in the area.
The evidence will demonstrate that the proponent has underestimated the risk of waste water spills and leaks, which leaves the Project vulnerable and poorly equipped to respond to the incidents that will inevitably arise. The combination of significant volumes of poor quality water being produced and manages across hundreds of sites in the project area over a period of 25 years, and the otherwise high quality of the groundwater hosted in the Pilliga Sandstone Aquifer (the predominant shallow aquifer in the region), and alluvium, raises significant concerns from an environmental and water management perspective.
The likely environmental impacts are so significant that the Project should be refused development consent.
 National Centre for Groundwater Research and Training (2013) ‘What is Groundwater’