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Upcoming field dye tracer study for the proposed outfall at Merimbula

In the coming weeks WRL will be running a dye dispersion field experiment for Bega Valley Shire Council, to help inform the EIA for a proposed wastewater outfall at Merimbula on the NSW far south coast. Over the past couple of decades WRL have developed the specialist techniques and equipment required to undertake field dye tracer studies both in the open ocean and in estuaries, and we have completed experiments for a range of outfalls across the Asia-Pacific Region including Sydney, Wollongong, Kiama, Newcastle, Christchurch, Jakarta and Manila. To read more about WRL's extensive outfall capabilities, visit:

Merimbula BayWRL engineer Alice Harrison, who is currently undertaking planning and preparations for the upcoming Merimbula dye dispersion testing, explains some more about the process:

“For ocean outfalls, we undertake dye dispersion tests to either investigate the currents and mixing processes within the ocean at a proposed outfall site, or to check and verify the performance and dilutions that an existing outfall is achieving.

During the experiment ocean currents are profiled using an ADCP mounted from the side of the investigation boat, and other atmospheric and ocean conditions such as winds and waves are also recorded. We typically use a special dye (Rhodamine WT) dropped into the ocean or injected at a treatment plant; that mixes with the ocean in the same way that a wastewater plume from the outfall would.

The dye is laced with a flourometric tracer, and we are able to profile the concentrations of the dye around the outfall site down to dilutions of 0.3 parts per billion using a Chelsea Mini-Tracka flourometer that is coupled with a Sea-bird SBE 19 Plus Seacat profiler. The results from the experiment allow us to quantify mixing processes and dilutions that will be achieved during certain environmental conditions, and can be used to inform other hydrodynamic and hydraulic modelling studies.”

WRL is hoping to undertake the experiment in Merimbula Bay this coming week, weather permitting.


Project Media

For further information contact:

Brett Miller | Principal Engineer - Hydraulics and Modelling |


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