Design and Construction Planning for Sydney's Sewerage Outfalls General Report June 1984

Deepwater submarine sewerage outfalls are planned from each of Sydney's three major ocean disposal treatment plants at Malabar, North Head and Bondi. The outfalls will dispose sewage through a tunnelled conduit linking with a diffuser on the sea floor, up to 3.5 km offshore, and so meet water quality objectives and protect beaches from pollution. A summary of the background to the project is given together with the reasons for choosing tunnelled outfalls. A description of the expected geology is followed by a brief outline of studies undertaken and key concepts for design and construction. The principle features of each outfall are described and the details of the diffuser design are given along with a discussion of the approaches considered for diffuser construction. The paper concludes with reference to the proposed construction programme and the estimated cost of the project.