Coal ash and coal ash repositories

Coal ash is the material remaining after coal is burnt to generate electricity.

The composition of coal ash depends on the chemistry of the coal being burnt. It is made up mainly of silicon, other minerals and trace elements such as metals and other matter.

Coal ash must be carefully dealt with to prevent risk to the environment and human health. Coal fired power stations store coal ash that isn’t reused in either dry emplacements, or wet coal ash dams. Collectively these are called coal ash repositories.

Ash repository locations and environmental risks

A range of factors influence how coal ash repositories can potentially impact the environment and human health including their:

  • environmental setting of the coal fired power station (geology, climate etc)
  • design of the initial storage (coal ash repositories are often old, unlined and may leach contaminants)
  • operational controls (dust suppression, surface/groundwater interception etc)
  • proximity to sensitive environmental values.

The 3 main pathways that contaminants from coal ash repositories can enter the environment are via leaching into groundwater, overflow into surface water and air mobilisation.

A precautionary advice is in place for mud and blue swimmer crabs caught in Lake Macquarie to limit consumption and reduce the risk of exceeding dietary intake safety levels.

Conceptual diagram showing the key transport pathways, potential impacts, and management responses associated with coal ash repositories.


In NSW, coal ash repositories are in the same sedimentary basins that contain NSW’s economically viable coal deposits. These basins are made of layers of shale, silt and coal that typically contain groundwater at various depths and with differing quality. Groundwater in these areas is often naturally high in dissolved salts and metals.

Surface water

If surface water is discharged from coal ash repositories, it may contain metals and other chemicals present in the coal. Minimising and managing surface water discharges from coal ash repositories reduces the risk to waterways and human health. In NSW, coal ash repositories are typically managed to avoid discharges to surface water except in all but the wettest periods. Strict requirements are in place to ensure that when discharges do occur, they are monitored, and limits are placed on the pollutants that are discharged.


The key risk to air quality is the ash that could be blown from uncapped coal ash repositories that are exposed to wind. Dust generation is minimised or prevented using dust suppression techniques such as misting and ultimately by progressive capping and closure.

Once dust is mobilised it can be transported across local air sheds and fall out. This has the potential to impact nearby water ways, bushland or urban areas.

Re-use of coal ash

The amount of coal ash re-used in NSW has grown in recent years. We support the reuse of coal ash where it:

  • is genuine, rather than a means of waste disposal
  • is beneficial or fit-for-purpose; and
  • will not cause harm to human health or the environment.

In NSW, the re-use of coal ash is regulated through the EPA’s Coal Ash Order (PDF 81KB) and Exemption (PDF 51KB) under the Resource Recovery Framework.

The role of the EPA

We are responsible for ensuring that the health of the community and environment are protected from the potential impacts of coal ash. We have a comprehensive and robust regulatory framework for regulating coal-fired power stations with coal ash repositories, primarily through environment protection licensing. Coal fired power stations are required to hold an environment protection licence (EPL) under Schedule 1 of the Protection of the Environment Operations Act (POEO Act) and are subject to a suite of other legislation the EPA administers including the Contaminated Land Management Act 1997 (CLM Act).

Regulating emissions to the environment

During the operational phase of coal ash emplacements, we regulate discharges to the environment through conditions in the EPLs to prevent or minimise environmental impacts and to protect human health. These conditions are based on a range of relevant site and case-specific considerations and include:

  • pollution that will be caused (or likely to be caused) and its impact on the environment
  • practical measures that can be taken to prevent, control, abate or mitigate the pollution and protect the environment from harm
  • practical measures that can be taken to restore or maintain those values.

Consideration is given to the risks of all discharges to the environment. The EPL sets out what is required of the licence holder to prevent or minimise pollution to surface water, groundwater or air.

In the case of discharges to water, the environmental values of the waterway that may be affected by the proposed discharge must also be considered. They are the community’s values and uses of water including aquatic ecosystems, drinking water, primary and secondary recreation, visual amenity, and water for irrigation, livestock and growing aquatic foods. The guiding principles are that:

  • where the environmental values are being achieved in a waterway, they should be protected
  • where the environmental values are not being achieved, all activities should work towards their achievement over time.

Where a potential environmental impact is identified after a licence has been granted (for example, where the nature of a discharge has changed, will change or the impacts are now better understood), we can vary the licence and attach new or revised licence conditions. These could require the licence holder to:

  • undertake pollution studies or pollution reduction programs to investigate the extent of the pollution and the impacts caused by the pollution (where this information is not available)
  • determine possible measures that can be taken to mitigate the pollution
  • implement additional requirements as needed.

Licence conditions include monitoring, assessing, and reporting on any environmental impacts, including coal ash repositories.

Breaches of the Act, its Regulations or licences may result in regulatory action in line with the EPA Prosecution Guidelines. All regulatory action is recorded and provided on the EPA’s Public Register.

Regulating contaminated sites

We have powers under the Contaminated Land Management Act 1997 (CLM Act) to manage contaminated sites including contamination associated with coal fired power stations. The Protection of the Environment Operations Act 2000 (POEO Act) and the CLM Act can both be used by the EPA to regulate contamination, post closure rehabilitation through to planning for alternative land uses. See sites that are being assessed or regulated under the CLM Act.

Parliamentary Inquiry into costs for remediation of coal ash repositories

The NSW Legislative Council’s Public Works Committee conducted an inquiry into the costs for remediation of sites containing coal ash repositories in NSW.

The EPA contributed to a Government submission to the inquiry and appeared before the Committee to respond to questions  on the regulation of coal ash repositories and additional questions raised at the public hearing.

The Committee tabled its final report on 22 March 2021. The government response to the report on 17 September 2021 outlines the EPA’s role in using its research agenda to assess the environmental condition around power stations, with an initial investigation of Lake Macquarie.

EPA actions

Regional and real time air monitoring data for licensed premises is available and we require monitoring of air and groundwater through EPL conditions.

Real time air data is available through the NSW Department of Planning, and Environment's Air Quality Monitoring Program which includes monitoring sites for the lower Hunter and Central Coast regions. A new monitoring site at Morisset on the Central Coast was commissioned in 2020.

In response to the Parliamentary Inquiry and in line with the NSW Government response, we engaged the aquatic science section of the Department of Planning and Environment to carry out a monitoring project in Lake Macquarie to better understand the current environmental condition and potential impact from coal ash repositories.

The monitoring program will take a ‘multiple lines of evidence’ approach to assessing environmental condition. Sampling commenced in March 2022 and will continue for 12 months. Sampling is being carried out at over 29 locations around the lake, collecting nearly 350 water samples and over 80 sediment samples.

Review of the regulatory approach to coal ash

Following the inquiry, we are reviewing the licence settings for discharges to surface water and groundwater monitoring to inform our regulatory requirements for ash repositories at coal fired power stations. Monitoring data over approximately the last 5 years is being analysed to identify where requirements for monitoring, reporting and discharge limits might need to change.

The review aims to establish a proportionate, risk-based program that provides an appropriate level of protection by preventing and minimising contamination discharged to surface water and the surrounding environment or leaching to groundwater from coal ash repositories.

Working with other agencies

The EPA and Dams Safety NSW have distinct responsibilities regarding the regulation of coal ash repositories. The EPA works with Dams Safety NSW on strategic regulation of prescribed coal ash repositories.

We work with the NSW Resources Regulator in relation to matters dealt with under the Mining Act such as tailings dams and mine rehabilitation. The Resources Regulator oversees the use of coal ash in old mines or to fill voids, but it has no role in regulating coal ash repositories from power generation.

Monitoring data

Each power station must carry out monitoring as required by their EPL and must publish the results on their web sites. The results of EPL monitoring together with other environmental reports can be found on each of the power station's webpages.

Coal fired power stations also provide NSW Treasury with environmental baseline studies.

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