Cook Shire Council understands the community’s concerns about the ongoing water discolouration and is committed to addressing the issue as quickly as possible. We want to reassure residents that the water meets all regulated drinking water standards.
We recognise that this is not the standard our residents should expect, and we sincerely apologise for the inconvenience caused. To help address your concerns, we’ve compiled a list of frequently asked questions to address common concerns and outline what’s being done to resolve the issue.
In the meantime, Council crews continue regular flushing of the network and have implemented pre-filter chlorination at the treatment plant, designed to trap oxidised minerals before they reach the reservoir.
We thank you for your patience and understanding as we work through this challenge and will provide further updates as soon as more information is available.
As always, community members are encouraged to log their concerns, queries or questions through our official channels, by calling 4082 0500 during office hours, or emailing mail@cook.qld.gov.au at your convenience.
FREQUENTLY ASKED QUESTIONS
Why is the water brown?
We suspect the discoloration is due to higher-than-normal levels of dissolved iron in the raw water. This is possibly caused by disturbances in the catchments from landslides and landslips during Tropical Cyclone Jasper, which exposed deposited thousands of tonnes of soil and rocks into rivers and waterways. These newly exposed soils and rocks may be contributing a completely new mineral composition to the waterways.
Why is this happening now, nearly 12 months after the floods?
During the dry season, waterways recede and water levels drop, leading to a higher concentration of minerals like iron in the raw water supply.
What has Council done since this issue was first reported?
We immediately reviewed the SCADA system, which monitors the treatment process, and found no evidence of errors or incidents.
We then flushed the mains, drained, and cleaned the reservoir. When we refilled the reservoir from the Annan supply, we noticed that the water was still discoloured.
Mains with lower water usage commenced daily flushing.
It was then identified that water coming from the plant was clear until chlorine was added as part of final treatment step. Chlorine is known to cause dissolved iron to oxidise and settle out of the solution, causing sediment and discolouration.
At this stage, investigation indicated that it is higher than normal levels of dissolved iron and minerals in raw water supply causing the discolouration.
Collected and sent water samples for specialist NATA Laboratory testing to confirm findings. Results are expected back on 6 December 2024.
As a temporary measure, we are installing a pre-filter chlorination system at the treatment plant. This will oxidize the iron before it reaches the filters. The filters then prevent sediment and discoloured water from entering the reservoir and flowing through into homes and businesses.
Why haven’t we switched to borefields?
Switching to the Borefields would significantly reduce available water supply, requiring the introduction of Level 4 water restrictions. Borefields can only produce 1 megalitre per day, while Cooktown currently requires 2.5 megalitres. Additionally, the Borefields produce water with similar discoloration issues. An approved capital works project, funded under Works for Queensland grant funding, will see the installation of a treatment process to remove this discoloration from the Borefields supply within the next two years.
Is the discoloured water issue in Cooktown unique, or are other areas experiencing similar problems?
The discoloured water issue in Cooktown is not unique and has been observed in other areas, including Cairns as recently as yesterday. Factors such as changes in water source conditions, high mineral content, hot temperatures, and maintenance activities can contribute to discolouration.
While the causes may vary slightly between regions, it is important to note that such issues are not uncommon and are often linked to natural environmental conditions or infrastructure maintenance. In Cooktown, the likely cause is elevated mineral levels resulting from landslides and flooding following Tropical Cyclone Jasper, combined with seasonal dry conditions.
What are the service standards for our water supply?
Cooktown’s water supply complies with the Australian Drinking Water Guidelines (ADWG) and the Cook Shire Drinking Water Quality Management Plan (DWQMP).
How often and where is the water tested?
Water quality testing is conducted regularly to ensure safety. Daily tests at the Cooktown Water Treatment Plant monitor turbidity, colour, pH, and alkalinity. While weekly tests check for E. coli and coliforms to ensure compliance under the ADWG and DWMP. Nine sampling sites across the reticulation system undergo comprehensive testing. Since the discoloration issue, E. coli and coliform testing has been increased to twice weekly.
What do the most recent test results show?
All results comply with the Australian Drinking Water Guidelines.
How do the recent tests differ from the specialist tests that were sent away, and why are the results taking so long?
The specialist tests expand the testing parameters to pinpoint the exact cause of the discoloration.
These tests require advanced equipment not available locally and must be conducted by specialist labs.
The delay is due to the time needed for transportation and processing in remote locations. Results are expected on 6 December 2024.