Blue Mountains investigation

Investigation

NSW Health and Sydney Water have confirmed that tap water in Sydney, including the Blue Mountains, meets Australian Drinking Water Guidelines and is safe to drink.

WaterNSW is conducting additional, targeted PFAS-related investigations to ensure Sydney Water and NSW Health have up-to-date information on the presence of PFAS in the catchment, so any risks continue to be managed appropriately.

Investigations include rigorous testing of water sources in the Blue Mountains’ catchment – including soil and water sampling – to investigate the source and causes of the elevated PFAS results. The extensive WaterNSW sampling program is occurring alongside work with multiple NSW Government agencies to explore other historical land use activities that potentially involved PFAS, such as firefighting.

Investigation of the Blue Mountains dams and catchment commenced in July, following Sydney Water testing which detected PFAS at levels below the Australian Drinking Water Guidelines at the Cascade water filtration plant.

Early water quality results indicate Medlow Dam is impacted by slightly elevated levels of PFAS. WaterNSW has disconnected Medlow Dam and Greaves Creek Dam from supply as a precautionary measure while investigations continue. The outcome of the investigation will inform the next steps WaterNSW will take to further mitigate risk.

Jump to section: What is being done?

Sydney Water has confirmed the water supplied from the Cascade water filtration plant to local communities is safe to consume and meets the Australian Drinking Water Guidelines.

What is the Blue Mountains system?

The Blue Mountains system sources water from within and outside the Blue Mountains catchments. These catchments are a small group of bushland valleys that feed water to Medlow Dam, Greaves Creek Dam and the Upper, Middle and Lower Cascade dams. The configuration of the Blue Mountains system is flexible, allowing us to take dams on and offline as needed to help us meet demand. The dams are all inaccessible to the public.

These five dams provide water for Sydney Water's Cascade water filtration plant at Katoomba, which supplies drinking water to the middle and upper Blue Mountains.

Supplies can be topped up when needed with water from Oberon Dam via a pipeline from the Fish River Scheme, west of the Great Dividing Range at Oberon.

What is being done?

PFAS contamination investigations are complex, due to the long-lasting nature of PFAS in the environment. This means that our investigation covers the entire Blue Mountains catchment and is drawing on information spanning a number of decades. As at 25 September, 2024, WaterNSW is taking the following actions:

Investigation

To better understand sources of PFAS in the Blue Mountains catchment, WaterNSW is:

Monitoring and testing soil and water throughout the catchment
We are undertaking rigorous testing of water sources and soil in the Blue Mountains’ catchment, with more than 100 samples from 30 sites, including water testing at various depths in the Blue Mountains dams.

Ensuring correct sampling collection, transport and analysis
Sampling, collection and transport are conducted by highly skilled professionals with strict protocols in place. Our partner labs have detailed steps that must be followed to ensure accurate analysis of our samples. This is essential to ensure that samples are not contaminated by everyday items that contain PFAS such as outdoor clothing, makeup, and sunscreen. Our monitoring teams are ISO 9001 certified, and all partner laboratories are NATA accredited.

Mapping land use across the catchment to help identify the potential source or cause of contaminants.

Investigating fire and firefighting history
WaterNSW is working with multiple government organisations including Rural Fire Service and NSW Fire and Rescue to explore historical land use including potential activities where PFAS has been used, such as firefighting activities.

Tracing drainage pathways through the catchment, such as sewerage and stormwater.

Engaging a contaminated site investigation specialist to provide tailored advice and ensure every avenue of enquiry is explored.

Developing a conceptual site model to understand the ways that contaminants may move from sources in the soil and water through the catchment, helping target sampling and evaluate options for mitigation.

Source water quality

To ensure the quality of source water supplied to Sydney Water for treatment as drinking water, WaterNSW is:

keeping Medlow Dam and Greaves Creek Dam disconnected from the supply network
frequently testing the Cascades dams and Oberon Dam source water
arranging to transfer additional water from Oberon Dam, which has recorded near zero levels of PFAS, to the Cascade dams to dilute PFAS levels
modelling the time frame required to dilute PFAS to inform our longer-term operating plan
working with Sydney Water to review the water supply system to ensure we continue to supply water safely and efficiently
ensuring our teams are ready to adapt to any changing conditions or new information as it becomes available.

Collaboration

WaterNSW continues to collaborate with experts and government agencies, including:

working closely with NSW Health and Sydney Water on investigations and our risk assessment
engaging PFAS contamination investigation specialists to collaborate with WaterNSW experts
engaging with the Rural Fire Service and NSW Fire and Rescue to better understand the use of PFAS for firefighting in the catchment.

Results

Medlow Dam and Greaves Creek Dam

Water Quality results indicate Medlow Dam being impacted by slightly elevated levels of PFAS. Whilst this dam does not supply the water filtration plant directly, Medlow Dam and Greaves Creek Dam were disconnected from supply on 7 August while further investigations are conducted.

Adams Creek

Catchment testing has highlighted a small creek in the upper reaches of the Medlow catchment that flows into the dam, Adams Creek, as an area for targeted investigations.

Indicative sample collection sites - current and planned

Water monitoring data results

Results will be published monthly.

Results of samples taken 27 September 2024 – Raw (untreated) water

These results reflect the untreated, raw source water in WaterNSW’s dams. This water is not supplied directly for use as drinking water, but is supplied to Sydney Water for treatment at the Cascades Water Filtration Plant.

For drinking water results, please visit Sydney Water.

Water source	PFOA (µg/L)	PFHxS (µg/L)	PFOS (µg/L)	PFHxS + PFOS (µg/L)
Greaves Creek Dam (1m depth)	0.0009	0.0319	0.0351	0.0670
Medlow Dam (1m depth)	0.0014	0.0450	0.0690	0.114
Upper Cascade Dam (1m depth)	<0.0005	0.0098	0.0136	0.0234
Middle Cascade (1m depth)	<0.0005	0.0034	0.0046	0.0080
Lower Cascade (1m depth)	<0.0005	0.0025	0.0034	0.0059

Results of samples taken 10 and 17-19 September 2024 – Raw (untreated) water

For drinking water results, please visit Sydney Water.

Water source	Sample date	PFOA (µg/L)	PFHxS (µg/L)	PFOS (µg/L)	PFHxS + PFOS (µg/L)
Greaves Creek Dam (1m depth)	10/9/24	0.0008	0.0229	0.0291	0.0520
Medlow Dam (1m depth)	18/9/24	0.0016	0.0524	0.0614	0.114
Upper Cascade Dam (1m depth)	17/9/24	<0.0005	0.008	0.0125	0.0205
Middle Cascade (1m depth)	18/9/24	<0.0005	0.0050	0.0053	0.0103
Lower Cascade (1m depth)	10/9/24	<0.0005	0.0023	0.0026	0.0049
Raw water supplied to Cascade water filtration plant	17/9/24	<0.0005	0.0082	0.0122	0.0204
Raw water from Oberon Dam supplied to Duckmaloi water filtration plant	19/9/24	<0.0005	<0.0005	0.0006	0.0006

Results of samples taken 3 September 2024 - Raw (untreated) water

For drinking water results, please visit Sydney Water.

Water source	PFOA (µg/L)	PFHxS (µg/L)	PFOS (µg/L)	PFHxS + PFOS (µg/L)
Greaves Creek Dam (1m depth)	0.0009	0.0264	0.0324	0.0588
Medlow Dam (1m depth)	0.0017	0.0485	0.0608	0.109
Upper Cascade Dam (1m depth)	<0.0005	0.0098	0.0127	0.0225
Middle Cascade (surface)	<0.0005	0.0051	0.0402	0.0453
Lower Cascade (1m depth)	<0.0005	0.0023	0.0027	0.005
Raw water supplied to Cascade water filtration plant	<0.0005	0.0113	0.0124	0.0237

Results of samples taken 16 August 2024 - Raw (untreated) water

For drinking water results, please visit Sydney Water.

Water source	PFOA (µg/L)	PFHxS (µg/L)	PFOS (µg/L)	PFHxS + PFOS (µg/L)
Greaves Creek Dam (surface)	0.001	0.0275	0.0315	0.059
Medlow Dam (surface)	0.0015	0.0456	0.0488	0.0944
Upper Cascade Dam (surface)	<0.0005	0.0098	0.0272	0.037
Middle Cascade (surface)	<0.0005	0.0035	0.0042	0.0077
Lower Cascade (surface)	<0.0005	0.002	0.0022	0.0042
Raw water supplied to Cascade water filtration plant	<0.0005	0.0092	0.0111	0.0203
Raw water from Oberon Dam supplied to Duckmaloi water filtration plant	<0.0005	<0.0005	0.0006	0.0006

Results of samples taken 31 July 2024 - Raw (untreated) water

For drinking water results, please visit Sydney Water.

Water source	PFOA (µg/L)	PFHxS (µg/L)	PFOS (µg/L)	PFHxS + PFOS (µg/L)
Greaves Creek Dam (surface)	0.0009	0.0244	0.0335	0.0579
Medlow Dam (surface)	0.0014	0.0398	0.0548	0.0946
Upper Cascade Dam (surface)	0.0005	0.0098	0.014	0.0238
Lower Cascade Dam (surface)	<0.0005	0.0019	0.003	0.0049
Raw water supplied to Cascade water filtration plant	<0.0005	0.0109	0.0136	0.0245
Raw water from Oberon Dam supplied to Duckmaloi water filtration plant	<0.0005	<0.0005	<0.0003	<0.0008

Frequently asked questions

Is Sydney’s water safe to drink?

NSW Health and Sydney Water have confirmed that Sydney’s water is safe to drink.

Learn more about Sydney Water's findings and monitoring.

Water goes through multiple levels of testing to ensure it is safe and meets the Australian Drinking Water Guidelines.

WaterNSW supplies untreated water, sometimes described as 'raw water' or 'source water', to Sydney Water and councils around NSW who then treat and supply the water to your tap. The Fish River Water Supply System is an exception. This process of testing and treating the supplied ‘source water’ we supply is rigorous, ensuring that drinking water that comes out of your tap is safe and meets the Australian Drinking Water Guidelines.

How is the Sydney drinking water catchment monitored?

Sydney’s drinking water catchment is 16,000 square kilometres – about half the size of Belgium.

Water quality monitoring across the catchment follows a targeted, risk-based approach to help ensure the treated water supplied for consumption meets the Australian Drinking Water Guidelines. Consistent with the government regulatory frameworks, the approach is based on expert advice from NSW Health and other authorities such as the Environment Protection Authority.

What testing is being done?

WaterNSW conducts routine testing across the Greater Sydney catchment to ensure the best quality water is supplied to Sydney Water, where it is further tested and treated to meet Australian Drinking Water Guidelines. Water goes through multiple levels of testing and treatment to ensure it is safe and meets the Australian Drinking Water Guidelines.

Get in touch

Questions can be submitted to our team at engagement@waternsw.com.au.

Blue Mountains investigation

Investigation

What is the Blue Mountains system?

What is being done?

Investigation

Source water quality

Collaboration

Results

Medlow Dam and Greaves Creek Dam

Adams Creek

Indicative sample collection sites - current and planned

Water monitoring data results

Frequently asked questions

Get in touch

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