STOCKTON OUTFALL

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Monitoring Results

Indicator Bacteria

Faecal coliform bacteria monitoring in the receiving waters to the north and south indicate that levels were within the primary contact recreation and protection of human consumers of seafood guidelines (MHL769 1997).

Biological Communities

Found no effects from the Stockton outfall.

Methods:

Undertook a biological study of soft bottom benthos that included sampling at Stockton Beach. A monthly soft bottom sampling programme was carried out at 9 sites (Belmont Beach, Burwood Beach, Stockton Beach, Dudley Beach, Merewether Beach, McMasters Beach and Avoca Beach) from March 1975 to February 1977. This study was primarily concerned with the effects of outfalls at Belmont and Burwood beaches. Five replicate samples were taken using a Shipek grab (0.04m2) and sediment grain size analyses were also undertaken.  

Found that sewage effluent:

• at times relatively high levels of some nutrients were observed at sites either close to or offshore of Stockton Beach, but many of these results are potentially confounded by the effects of discharges from the Hunter River. Conclusions by Laxton & Laxton (1986) were that the presence of the Stockton outfall caused only a slight elevation to the mean of total phosphorus.

General findings (not necessarily related to outfall):

• The benthos in 10 m of water off Stockton Beach was affected by periods of heavy swell.

• It was composed of small crustaceans, polychaete worms and molluscs which live buried in the sand.

• There were large bivalves (Austromactra sp. and Donax deltoides) living in the area.

• On occasions, large aggregations of the small gastropod Bankivia fasciata were seen living on the surface of the sand.

• The mean number of species (and mean densities) per sample varied from year to year with no consistent difference between the numbers of species living at control sites or experimental sites.

•  Heavy metal concentrations in the sediments were low and there was no significant difference between control sites and experimental sites  (Laxton and Duell 1990).

Methods:

Laxton and Laxton (1986) commenced a sampling program in January 1985 to investigate the water column, water chemistry, pelagic biology and benthic communities of sedimentary and rocky bottoms.  Benthic soft substrate fauna was sampled at 3 experimental (close to outfall) and three control sites.  Benthic sampling of sedimentary areas was carried out by removing 200 X 200 X 100 mm sections of the sea bed using a diver operated device (aluminium container). The animals living in the substrate were separated from the sand by passing the material through a 1mm sieve. This experiment was conducted in 10 m of water off Stockton Beach. The control area was located about 1.5km south of the outfall. Samples were collected every 6 months in 1985 and 1986 and annually in 1987, 1989 and 1990 (Laxton and Duell 1990). For the first 2 years, water quality studies were also being undertaken (once a month) as close to Stockton outfall as possible and at a location seaward of the outfall (approximately 2km). Control stations, both an inshore and an offshore site, were located at the far northern and far southern ends of the study area (between Port Stephens and Catherine Hill Bay).  Samples of sediment were also collected at each control and experimental site in 10 m of water at Stockton Beach in July 1990 and examined for heavy metal concentrations.

Outfall Site

Faecal Coliform

Outfall

Outfall

Stockton

(Stoc_7) Last updated May 2000