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Merimbula Sewage Treatment Plant Upgrade and Deep Ocean Outfall

Project Overview

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Bega Valley Shire Council is taking action. Advice from the NSW Environment Protection Authority (EPA) and the community is the existing beach-face outfall and dunal exfiltration ponds at Merimbula Sewage Treatment Plant are not sustainable. Council is working with AECOM to develop a concept design and environmental assessment for a deep ocean outfall and upgrade of the STP.

More fieldwork ahead in Merimbula Bay - December 2017

More fieldwork ahead in Merimbula Bay - December 2017

We’re continuing fieldwork to gather more information about Merimbula Bay. This will help our project team develop location options for the deep ocean outfall and STP upgrade.  

Starting this week, we are doing hydrographic surveys. This means scientists in boats will be measuring the physical parts of the bay like water depth, surface of the seabed and the shoreline. 

Throughout October and November, we surveyed the marine ecology in the bay to better understand habitats and refine existing maps of the area. We used underwater videos at selected locations to identify habitats and groups of fish. Abalone fishing is vital to the economy of the area. We included specific surveys to assess the abundance of abalone in shallow sub tidal reef areas.

In early September, we did flora and fauna surveys to list the different plants and animals in the area between the STP and Merimbula Bay. This information will help us understand the area’s variety of plant and animal life, and minimise impact from the project.

We carried out dye dispersion tests in Merimbula Bay earlier this year in August. We released a harmless, bright red fluorescent dye into the water at several locations in the bay, including Haycock Point (east and north). This information will show how waterborne materials travel and spread in the bay. It will help our designers understand how water flows there. We will do this testing again in the warmer weather.

Dye Testing in Merimbula Bay - August 2017

Dye Testing in Merimbula Bay - August 2017

Bega Valley Shire Council will carry out dye dispersion tests in Merimbula Bay in August, weather permitting.

With Council commencing an environmental assessment process and developing a concept design for the Merimbula Sewerage Treatment Plant (STP) Upgrade and Deep Water Ocean Outfall, the testing is critical to the hydrodynamic modelling for the project.

Council’s Water and Sewerage Services Manager, Jim Collins, said Council is acting on advice from the NSW Environment Protection Authority and also local community concerns, that the existing beach-face outfall at Merimbula STP is not sustainable.

“The information we receive from these tests will show the dispersion rates and travel times of waterborne materials in the bay, and will help our designers determine the best location for the placement of the deep water ocean outfall,” Mr Collins said.

“The process will involve Council’s consultant hydrologists releasing a harmless, bright red fluorescent dye called Rhodamine into the water at up to four locations in the Bay, including Haycock Point (east and north) and Merimbula Embayment.  

“The exact timing of the testing is dependent on weather and ocean conditions; however Merimbula Bay will be open and safe for all water users during the tests.

“Rhodamine, which will disperse rapidly, follows the pathways of currents closely and has a low impact on water quality. It will be used to measure how long it takes the currents to move water between predetermined sampling sites, with the testing set to take a few hours in each location,” Mr Collins said.

Photograph:  Merimbula Bay looking south towards Pambula Beach and Haycock Point with the Pambula Merimbula Golf Course and Merimbula Sewage Treatment Plant in the foreground.

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