Monitoring the environmental condition of Lake Macquarie

We are monitoring the environmental conditions near power stations in Lake Macquarie to assess the current condition, provide a basis for comparison in the future and contribute to any future remediation activities.

What we are doing

The NSW Government response to the Public Works Committee ‘Inquiry into the costs for remediation of sites containing coal ash repositories in NSW’ committed the EPA to understanding the impacts of coal ash on the environment through its research agenda. Lake Macquarie was chosen as an initial step in the NSW Government’s response to the inquiry.

Why we are monitoring in Lake Macquarie

There is a long history of industrial and urban activity around Lake Macquarie. The impacts of this activity have been extensively studied by a range of government and other organisations over a long period of time.

As industry around the lake (such as power stations and coal mines) begins to transition to other activities and urban land use continues to expand, there is an opportunity to establish a new baseline of information on the environmental condition of the lake in the vicinity of the power stations. The monitoring program will focus on the areas in the vicinity of the power stations and assess the current environmental condition, determine contaminant levels, and quantify impacts on Lake Macquarie’s biota.

The environmental assessment will provide a robust foundation to compare future changes in environmental condition and inform any future remediation activities.

Lake Macquarie, Central Coast NSW, Australia. The location of the ash dams is indicated with a green plus symbol.

What the study involves

Sampling of Lake Macquarie commenced in the second week of March 2022 with sampling of surface water at 29 power station and lake sites. Sampling will run for 12 months – collecting around 350 water samples and over 80 sediment samples. Up to two wet weather events will be sampled if rainfall exceeds 30mm in the previous 24 hours. Collection of surface sediment samples commenced in August 2022. Core samples will be collected at representative locations based on the results of the surface sediment sample analysis. Eighty surface sediment samples and 10 sediment cores will be collected.

Samples will be analysed for analytes including 20 total/ dissolved metals, total suspended solids, and nutrients. Surface water results will be screened against the Water Quality Guidelines (ANZG 2018). Analysis of surface sediment samples will help us determine potential impacts on ecological receptors by understanding the distribution and levels of contamination in the lake. Additional surface sediment sampling will be taken to undertake benthic community ecological assessment by looking at the types of invertebrates present. Sediment cores will be analysed in segments to determine contamination levels over time.

The study will investigate 4 key lines of evidence:

  • surface water quality sampling: determining the concentration of present-day contaminant inputs
  • surface sediment sampling and sediment depth profiling: mapping the contaminant distribution in sediments and measuring change over time
  • sediment ecotoxicity testing: potential risk to ecological receptors from the cumulative effects of all bioavailable contaminants
  • benthic ecological assessment: impact on the benthic invertebrate community and ecosystem health.


The water samples will be collected to help determine the concentration of present-day contaminant inputs. Samples will be analysed for the following parameters and results will be screened against the Water Quality Guidelines (ANZG 2018).


Total metals and Dissolved metals

Silver (Ag), Aluminium (Al), Arsenic (As), Boron (B), Barium (Ba), Beryllium (Be), Cadmium (Cd), Cobalt (Co), Chromium (Cr), Copper (Cu), Iron (Fe), Lead (Pb), Manganese (Mn), Molybdenum (Mo), Nickel (Ni), Selenium (Se), Thallium (Tl), Vanadium (V), Zinc (Zn) and Mercury (Hg)

Total recoverable low-level mercury

Dissolved mercury

Total suspended solids

Dissolved organic carbon




Free Reactive Phosphorous

Total Nitrogen and Total Dissolved Nitrogen

Total Phosphorous and Total Dissolved Phosphorous

Monthly surface water quality sampling will be undertaken over a 12-month period to determine the range of ambient concentrations in receiving waters. Surface water quality samples will be taken at 29 locations within Lake Macquarie. This includes the lake in the vicinity of coal ash dams, waterway discharges from the power station, and reference locations in both the southern (Nords Wharf and Swansea) and the northern (Belmont Bay and Toronto Bay) section of the lake.

Two additional sampling events will specifically target wet weather events if more than 30 mm of rainfall occurs in the previous 24 hours. Wet weather event sampling is included to collect information about potential delivery of additional contaminants to waterways.

Lake Macquarie surface water monitoring sites

Surface sediments will be collected from 80 sites across the lake and results will be used to develop contour plots for metals/ metalloids of concern. Surface sediments will be analysed for the following parameters.


Total recoverable metals: Silver (Ag), Arsenic (As), Boron (B), Barium (Ba), Beryllium (Be), Calcium (Ca), Cadmium (Cd), Cobalt (Co), Chromium (Cr), Copper (Cu), Iron (Fe), Lithium (Li), Manganese (Mn), Molybdenum (Mo), Nickel (Ni), Lead (Pb), Antimony (Sb), Selenium (Se), Tin (Sn), Strontium (Sr), Titanium (Ti), Thallium (Tl), Vanadium (V), Zinc (Zn)

Total mercury

Acid volatile sulfide and simultaneously extracted metals

Moisture content

Grain size


Total organic carbon

Surface sediments will be collected from 80 sites in Lake Macquarie and from waterways leading from the power stations to the lake. Surface sediment sampling will investigate contaminants that are bound to particles that may settle to the lake or riverbed where they are stored, overlayed with sediment or resuspended in the water column. Targeted core sampling will be used to determine potential ecotoxicity impacts to help assess the likelihood of sediment impacts on ecological receptors. The bulk of the samples will be collected in the southern end of the lake at locations in the vicinity of the coal fired power stations.

Sediment cores will be collected from 10 locations and sectioned into intervals to understand changes in contaminant levels over time. The core samples will be analysed for total metals, moisture content, grain size, pH, and total organic carbon.

Sampling sediment cores will help us understand changes in sediment quality over time. The sediment depth taken will cover the period until before the operation of power stations in the lake catchment - approximately 1950. This is considered the most appropriate period for comparing changes in contaminant concentrations over time. The preliminary sites have been selected to provide representation within key areas of the southern section of the bay where secondary sampling will occur for chemical analysis.

Healthy sediments generally have a high diversity of macroinvertebrates, including species sensitive to pollutants. Unhealthy sediments generally only have a few types of hardy, pollution tolerant macroinvertebrate species.

Sampling locations for the benthic community ecological assessment will be determined based on the results of the surface sediment chemical analysis. Up to 20 sites will be selected and will include a mix of representative locations in the southern end of the lake and reference locations will also be sampled for comparison purposes. Within each of the sites, three replicate cores will be collected (i.e., up to 60 individual cores will be collected). Confounding factors such as sediment grain size, water depth and physico-chemical properties of the overlying water will also be taken into consideration during site selection.


Will the monitoring be comprehensive and independent?

Yes, the EPA has commissioned the Department of Planning and Environment to undertake the monitoring. A monitoring plan was designed by expert water quality scientists and ecologists in the Department of Planning and Environment and peer reviewed by external experts. They will also prepare the final assessment report to be peer reviewed by independent external experts to ensure its scientific integrity.

How will we involve the community and stakeholders?

Prior to starting the project, we engaged with power stations and the Hunter Community Environment Centre (HCEC) and they provided input into sampling sites selection.

We will continue to provide updates to the community on the project through our webpage and provide the final report when it is completed and been peer reviewed.

What about human health impacts?

The EPA will consider risks to human health based on the results of the monitoring. NSW Health is responding to Recommendation 6 of the Inquiry and will propose health study types that are able to address the community's health concerns.