WONGA OUTFALL

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Monitoring Results

Indicator Bacteria

Extensive monitoring of faecal coliform bacteria in the receiving waters at Shelley Beach and Bateau Bay (and Boat Harbour, Laxton and Laxton 1978) indicate that the guidelines for primary contact recreation and protection of human consumers of seafood are met within a 500 meters of the outfall.

Biological Communities  

Laxton & Laxton (1978 & 1980)

Found that sewage effluent:

  • Only slightly lowered the salinity of the surface water during periods of calm seas and low swell.

But found no effect on:

  • the development of the rocky bottom community at Wonga Point.

  • Water clarity in the vicinity of the outfall.

  • Sediment accumulation on the sea bed

General findings (not necessarily related to outfall):

  • Benthic communities were very similar at all locations examined.

Methods:

The benthic component of rocky bottom communities living at Wonga Point, Crackneck Point and Little Cove (First Point) were examined (using photo quadrats).

Marine Pollution Research (1992)

General findings (not necessarily related to outfall):

  • A small number of organochlorine pesticide residues were above the detection limits.

  • Concentrations of DDT, DDD and DDE were found above detection limits in a small number of fish (mostly in red morwong), but the muscle tissue levels recorded were well below the NHMRC recommended limits for human consumption (now superseded by the NFA (Anon 1984) limits).

  • Chlordane was detected in the livers of four red morwong samples (maximum 0.1ppm).

  • Tunicates (Herdmania sp) from two sites (Broken Head and Wonga Point) had consistently low concentrations of all organochlorine compounds for all replicate samples. With the exception of chlordane, these concentrations were all below the NHMRC limits for edible fish and shellfish [note that Herdmania is not a fish or shellfish and is unlikely to be used as a food source].

  • Concentrations of organochlorine compounds in tunicates at Norah Head and Wybung Head were all below the level of detection. 

  • Concentrations of PAH compounds and total PAH in red morwong muscle tissue were all below detection limits.

  • Concentrations of individual PAH compounds in liver samples were below detection levels and total PAH concentrations (the sum of individual PAHs) in liver samples were all less than 1.6 mg/g.

  • Heavy metal concentrations in the fish muscle tissues were above the detection limits but well below NHMRC recommended levels for human consumption.

  • Higher levels of trace metals were often found in the liver tissue samples, but there are no NHMRC (or NFA) recommended levels for fish liver tissue.

  • Statistical analysis of metal concentrations between sites showed no definitive outfall effect.

Methods:

MPR (1992) investigated the bioaccumulation of synthetic organic compounds and heavy metals in a number of marine organisms found at or near the outfall. They collected two species of fish (10 individual red morwong (Cheilodactylus fuscus) and 5 individual rock cale (Crinodus lophodon)) and one species of sessile tunicate (Herdmania sp. – at least 10 individuals) from four sites (Broken Head, Wonga Point, Norah Head (the site of another ocean outfall – see Norah Head outfall) and Wybung Head). Fish muscle and liver tissue and homogenised tunicate tissue were tested for organophosphate pesticides, herbicides and synthetic pyrethroids, carbamates, organochlorine pesticides, PAH compounds and heavy metals.

Red Morwong

Faecal Coliform

Outfall Site

 

Kelp

Limpets

Outfall Site

 

Hormosia

 

Wonga 

  

(Wong_7) Last updated June 2000