CONISTON BEACH OUTFALL

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Physical Environment

Landscape

Coniston Beach consists of Quaternary sand dunes (Wollongong Geological Series Sheet SI 56-9) which are aeolian (wind formed) north-south oriented dunes 5-15m high. Soils consist of deep calcareous sand on the beaches, siliceous sands on the foredunes and isolated podzols in the swales (Patterson Britton & Partners, CEE & AWT 1998).

Bathymetry & Substrate

The outfall is located approximately 200m offshore of Coniston Beach in 7m water depth close to a relatively large area of rocky reef. The soft seabed in the vicinity of the outfall ranges from fine to medium sands nearshore (to approximately 7m water depth) to coarse sand, shell grit and clay further offshore. Fine sediments occur at the 10m contour, while coarse sediments are found at the 16m depth. Sediments at 18m and 20m water depth are coarse sand, shell grit and gravel. Small areas of clay were observed approximately 600m offshore and to the south-east of the existing outfall and 300mm below the sand 50m south of the reef on the 18m depth contour. A large irregular sandstone reef extends immediately offshore from the existing outfall from the 7m depth contour to the 20m depth contour. This reef extends approximately 250m north and south of the existing outfall alignment. Within the reef, there are rock outcrops and pinnacles, areas of flat rock 10 to 30m across and sand patches (Patterson Britton & Partners, CEE & AWT 1998). To the north of Coniston Beach is Wollongong Beach and then Flagstaff Point. To the south is a boulder seawall (the Port Kembla Coal Loader Stockpile) and Port Kembla Harbour.
Currents, Winds and Waves

Climate, wind and oceanographic data for the area are available from AWT (1992a) and Patterson, Britton & Partners, CEE & AWT (1998).

Recent studies by Lawson and Treloar (1998 cited by Sydney Water Corporation 1999) indicate:

- a net current to the south averaging 4 cm/s.

- southerly currents occurred much more frequently than northerly currents, which in turn occurred more frequently than offshore/onshore currents.

- measurements over a one month period revealed that currents were weak, with longshore currents averaging 4cm/s and onshore/offshore currents averaging 2cm/s.

- Further oceanographic data using a moored acoustic doppler current meter (ADCP) 800m due east of Coniston Beach is described by OFS (1998).

Outfall Site

Diffuser Head

Outfall Site

Diffuser Port

Coniston Beach

(Coni_5) Last updated May 2000