Turbidity monitoring

Turbidity is a measure of the cloudiness in water caused by suspended material.  During the project, this will be managed throughout the project using an adaptive management approach and real-time monitoring.

Turbidity is measured in Nephelometric Turbidity Units (NTU). Should the nominated NTU limits set by the EPA be exceeded, the dredge contractor will take action and either adjust or cease dredging.   The limits and actions are summarised below


Turbidity monitoring data – updated hourly below

The line graphs show the median level of turbidity recorded by each monitoring buoy, calculated over a rolling 6 day and 15 day median.  If turbidity increases due to dredging activities, the D1 and D2 lines on the graph will rise.

If turbidity has increased due to background conditions unrelated to dredging, for example, due to a storm or weather event, B1 will rise on the graph. If B1 rises, D1 and D2 may naturally rise too and follow a similar line. Remember to refresh your browser to make sure that you have the most current data. Please note that the Turbidity Monitoring Data is best viewed on a desktop computer.

Dredging activity summary

  • Dredging commenced 7 June 2019
  • A rise in background turbidity levels (B1) occurred mid July due to prolonged strong winds and wet weather. Consequently, there was also a rise in turbidity levels immediately adjacent the dredge area (D1 and D2), with levels reaching HOLD on 19 July
  • Dredging stopped when HOLD levels were reached
  • Following further assessment, the EPA approved the recommencement of dredging with operational restrictions in place until the HOLD levels declined
  • As weather conditions improved and through effective dredge management, turbidity levels fell below HOLD on 28 July. As a result, the operational restrictions were lifted
  • There were strong winds for a few days from 8 August
  • Turbidity reached HOLD on 10 August and all dredging ceased
  • After further assessment, the EPA approved recommencement of dredging with the Backhoe Dredge on 11 August and Trailing Suction Hopper Dredge on 12 August, with both permitted to dredge under specific operational restrictions.
  • Turbidity reached HOLD on 19 August and all dredging has ceased

Click here to read the latest project update. 


The gauges show the results on the graph in another format. If turbidity reaches ALARM or HOLD, this will be clearly stated on the gauges. Remember to refresh your browser to make sure that you have the most current data.


Dredge plume monitoring site 1 (D1)



Dredge plume monitoring site 2 (D2)



Background monitoring location (B1)

6 Day Rolling Median

15 Day Rolling Median

Satellite Imagery

The satellite imagery below is processed using algorithms to illustrate the turbidity plumes.  Remember to refresh your browser to make sure that you have the most current data. Please note that the images below indicate cloud cover, shown as white/grey clouds in the MODIS True Colour image, and as black patches on the MODIS Derived NTU image.  Turbidity is shown by the Turbidity Heat Map.

Historical Turbidity Monitoring

Turbidity monitoring commenced in July 2018 to gather baseline data on background turbidity levels prior dredging commencing. Below is a summary plot of the approximately 11 months of turbidity data collected prior to commencement of dredging in June 2019.


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