Unfortunately, the south end of Blackmans Bay beach has been downgraded to poor as a result of the outcomes of the 2023-24 sampling program. This means that swimming is not advised in this location. It is generally safe to swim at the rest of the beach.
What does a “Poor” rating mean?
This doesn’t mean the water quality is poor everyday at the south end of the beach, as test results show that 81.5% of our samples over the last 5 years have passed. The long-term rating is based on five years of sampling data with only 5 significant failed samples needed during that period for the water quality rating of a beach to be downgraded. 
Why is this happening?
At Blackmans beach we have four (4) stormwater outfalls, three (3) of which are located at the southern end of the beach. This is required to take the runoff from all the roofs and roads from the hills above the beach after rainfall. This stormwater can carry contaminates such as animal faeces, rubbish and sewer spills. These three stormwater outfalls are supplied with the vast majority of Blackmans Bay stormwater generated in Blackmans Bay. Which includes stormwater from 2,500 properties within Blackmans Bay Beach and are transported through more than 60km of pipes and assets to the beach. There is also over 20 km of roads surfaces within the catchment of these three outfalls.
What is Council doing?
Over the past five years, we’ve undertaken extensive investigations into how contaminants enter the stormwater network. This includes over 700 additional water samples from the beach, waterways, and stormwater outfalls, along with more than 1,000 ammonia tests conducted across 60+ kms of stormwater pipes in Blackmans Bay.
This work has allowed Council to trace sources of contamination entering the stormwater network and address issues in partnership with TasWater. While our efforts are ongoing and we continue to identify various sources of contamination, our investigations have not yet revealed a single clear reason for the beach’s occasional water quality failures.
In response to the southern end of Blackmans Bay Beach downgrading to “Poor”, as a result of the Derwent Estuary Recreational Water Quality monitoring last year, investigations into water quality at the beach will be expanded in 2025. This will focus on the catchments above the beach, including expanded surveying of the stormwater network for contamination. One possible contamination source is from sewage in places where stormwater pipes are compromised, and sewerage infiltrates from nearby sewer pipes.
Council is continuing to work with our partners – the Derwent Estuary Program (DEP) and TasWater, to track and trace the source of potential bacteria issues and assess existing sewer and stormwater infrastructure in the Blackmans Bay catchments.
Over the summer period weekly test results will be available on the DEP website as part of the formal Beach Watch monitoring program that the Derwent Estuary Program coordinates. Beach Watch | Derwent Estuary Program
What can you do?
Be aware that anything that you put into the stormwater network will wash out at the beach. Whatever gets washed down the drains on all our streets ends up in our waterways and beaches. Do not flush unsuitable items into the toilet that could contribute to blockages and spills in the sewer network. Report water leaks and sewer spills to TasWater. In dry weather if you see water flowing over roads and walkways please report to 136 992 number TasWater as soon as possible.
FAQ’s
Is the southern end of Blackmans Bay beach closed?
No, the beach is not closed.
Council cannot stop the public from accessing or using the beach. However, we do not currently recommend swimming in the southern section of the beach due to the new long-term “Poor” water quality rating.
This area will be clearly signposted to make members of the public aware of the impacted area.
What exactly has been detected in the water?
Enterococci is the indicator used in the summer monitoring program.
Enterococci levels in these samples are measured in cfu/100ml (colony forming units per 100mls).
Enterococci is a faecal bacterium that in indicative of the presence of sewerage but can also be present from other natural sources in the environment such as agricultural runoff, birds and animals faeces.
Water contamination by sewage and animal faeces may pose a health hazard when the water is used for primary contact recreation, such as swimming.
Is the water always contaminated?
No. The beach rating is based on a long-term grading system.
The long-term rating is not a representation of what the water quality is like from one day or one week to the next. The rating is based on the last five (5) years of sampling data.
Why has the beach been given a poor rating?
When a monitoring site at a recreational beach records five (5) results over the trigger level, then that beach shall be given the rating associated with the below:
Five (5) results in five years that are above 280 = “Fair” rating.
Five (5) results in five years that are above 500 = “Poor” rating.
The southern section of the beach has been classified with a “Poor” grading, as there has been 6 results out of 87 that exceeded the threshold (500 cfu/100ml); over the last 5 years.
What is the process of reviewing the beach grading?
Following every summer swimming season, the sample results are added to previous results, and the results from five years of sampling are collectively used to calculate a new long-term rating by the Derwent Estuary Program.
I went swimming in the ‘poor’ section, will I be, okay?
It is unlikely that you will become sick.
As always, if you are concerned, we would encourage you to talk to your GP or other healthcare professional.
The trigger levels for enterococci are set by the National Health and Medical Research Council and are based on the amount of ingestible portions that a swimmer is likely to consume on an annual basis.
Regular swimmers will have a greater exposure and are assumed to ingest a larger amount of water annually.
Why is the contamination only affecting the southern end?
Council is continuing to investigate why Blackmans Bay South’s water quality is impacted by contamination from time to time whereas the middle and North sites are not. Investigations undertaken to date have not been able to identify any clear correlation between possible contamination sources and water quality at the Southern end of Blackmans Bay.
While we cannot point to the exact cause of the high results recorded at the southern end of Blackman Bay Beach we do know that there are 3 stormwater outlets in the area. Standard public health advice is to not swim close to stormwater outfalls and after heavy rain.
Council is looking into options in partnership with TasWater to reduce contamination into the stormwater that drains to this location. This is not a quick solution and requires extensive investigations to develop a staged plan moving forward.
What is Council doing about the contamination?
Council has a dedicated Stormwater Investigations Officer who undertakes weekly sampling to track and trace potential sources of contamination.
Council is currently examining the stormwater network in the Blackmans Bay area including in particular the network which drains out in the southern end of Blackmans Bay beach. This will focus on the catchments above the beach, including expanded surveying of the stormwater network for contamination. One possible contamination source is from sewage in places where stormwater pipes are compromised, and sewerage infiltrates from nearby sewer pipes.
Council will also continue to work with our partners – the Derwent Estuary Program and TasWater, to tract and trace the source of any potential bacteria issues and assess existing sewer and stormwater infrastructure in the community.
Is it the seagulls?
Highly unlikely. Previous investigation into seagull numbers and water quality found no clear links between the seabirds and the contamination in the area.
While it’s difficult to absolutely and conclusively rule out that the sea birds are a contributing factor, as enterococci is known to be present in bird faeces. There have been periods of extremely high seagull numbers on the beach and simultaneously very good water quality samples results. Along with times when there is very poor water quality during time when there are very few, or no seagulls at all.
Can Council extend the stormwater pipes further out into Derwent?
Council could extend the stormwater pipes further out into the Derwent River though this would be a multi million dollar project which would require either Federal or State funding or be spread over many years of Kingborough Council Capital funding. There is no conclusive evidence that this would solve the issue.
What can I do to help prevent contamination of the Derwent estuary?
Be aware that anything that you put into the stormwater network will wash out at the beach. Whatever gets washed down the drains on all our streets ends up in our waterways and beaches.
Report water leaks and sewer spills to TasWater. In dry weather if you see water flowing over roads and walkways please report to 136 992 number TasWater as soon as possible.
How will Council keep the community updated?
Keeping our community updated is an important priority for Council.
Over the summer period weekly test results will be available on the DEP website as part of the formal Beach Watch monitoring program that the Derwent Estuary Program coordinates. LINK
Council will also regularly update its social media channel and website with any further developments and continue to work with the local community in keeping them informed of future developments.