Improving Water Quality

We have focussed on the recreational water quality of Blackmans Bay Beach (south) over the past year, following some poor results and a rating of ‘poor’ from the Derwent Estuary Program. The southern end is defined by where the large stormwater outfall extends into the water.

Our officers have carried out intensive investigation into the issues at the southern end of the beach. We have worked with TasWater to identify issues, carry out repairs and develop solutions, such as the low-flow diversion from stormwater to sewer, to improve the water quality.

The investigations and actions from the past year include:

  • Weekly beach and stormwater sampling program from November 2018 (included beach and stormwater outfalls).
  • TasWater and the Derwent Estuary Program also conducted marine based sampling during this period.
  • Source tracking of contamination.
  • Identification and rectification of a number of illegal domestic cross-connections.
  • The formation of a Joint Investigative Team between Council and TasWater.
  • Collaboration with TasWater to identify damaged sewer infrastructure within the catchment area.
  • A short-term trial diversion system at the Illawarra Road outfall (note: this was unsuccessful beyond a few weeks).
  • Working with TasWater for approval to divert low-flows of stormwater to sewer.
  • Installation of Illawarra Road and current installation of Blackmans Bay mid outfall low-flow diversions of stormwater to sewer.
  • Monitoring the number and location of seagulls at the beach.
  • Sand sediment sampling.
  • Engagement of a consultant with a specialist background in water quality issues and particularly the Derwent Estuary.
  • Active participation in a Source Tracking Working Group with the Department of Health, TasWater, EPA, Derwent Estuary Program, City of Hobart and the Clarence City Council.
  • Appointment of a permanent full-time Stormwater Investigation Officer to focus on stormwater impacts on recreational water quality.

Below are some frequently asked questions about the investigations. If you would like further information, contact our Environmental Health Officers on 6211 8200.

 

Is the southern end of Blackmans Bay Beach closed?

Council does not have the ability to close or prevent access to a beach.

However, if a beach is rated as ‘poor’ as part of the Derwent Estuary Program’s long term rating system, we are required to advise people not to swim at the location.

 

If recent sampling shows that the water quality is good now, why can’t we swim there?

The rating system is based on five years of data (a five year average).  A poor year of results will ordinarily take five subsequent years to fall out of the five year average.

We need to collect more data, particularly over summer, to show that the results are good over a longer period of time.  We then need to work with the Director of Public Health and the Department of Health to look to review the grading.

Can I swim at the rest of the beach?

Yes.  The poor water advice is for the south end of Blackmans Bay beach only.  The entire section of the beach that lies north of the large concrete stormwater pipe is recommended for swimming.

What is Council doing now?

Council has recently installed a low-flow diversion at the Illawarra stormwater outfall.  This will divert the low-flows of stormwater to the TasWater sewer network.

This means the system should catch any contaminants that are coming through the stormwater system.

The low-flow is not designed to divert any rainfall. The advice to not swim after heavy rainfall remains in place, due to the increase in water flowing over the land and through the system before entering the marine environment.

Council will continue to sample the stormwater outfalls and investigate issues further up the catchment.

The Environment Protection Authority is also currently conducting nutrient and sterol analysis in the Kingston Beach and Blackmans Bay catchment areas over the duration of the summer swimming season.

Were the seagulls a factor in the poor water quality?

Initially the arrival of the seagulls coincided with poor water quality. However, recent periods of good water quality results have been observed with very large numbers of seagulls present on the beach, indicating that the seagulls are not likely to have been the primary cause of the poor water quality results.

What is the process for reviewing the beach grading?

Requesting a review of the beach grading, outside of the normal five year average grading process, requires a collaborative approach with the Director of Public Health and the Department of Health.  Council needs to demonstrate that substantial steps have been taken to remediate the problem, as well as demonstrating that the water consistently complies with the Recreational Water Quality Guidelines.

Council’s investigations have led to various cross connections and sewer leakage issues being rectified in the catchment area. The installation of the low flow diversions are also a significant investment in protecting beach water quality and amenity.

When would a review of the rating happen?

Sampling results have shown that the water quality at Blackmans Bay South has been very good since June of this year.

To have confidence that we have taken effective actions to address the water quality, Council needs to demonstrate compliant sampling results over the duration of this upcoming summer season.

If the good results continue, Council is planning on collaborating with the Director of Public Health and the Department of Health to seek a review of the grading, outside of the normal five year average grading process.  The timing of this is still to be confirmed but it will be when there is a consistent amount of good results (over 12 months).