Pulling an Outfall Seaward along the Ocean Floor

The Black Rock Ocean Outfall Pipeline has been constructed by the Geelong and District Water Board to replace an existing shoreline discharge which was first commissioned in 1916. Together with an onshore screening plant the outfall pipeline will provide disposal facilities to handle domestic and industrial wastewater from the Geelong area and a number of smaller communities on the Bellarine Peninsula, and the town of Torquay. The Outfall has been designed to handle flows up to the year 2040 and discharges 1.2 km offshore from Black Rock into 15 metres depth of water providing a minimum initial dilution of 50:1. A cement mortar lined steel pipe has been used with an external corrosion protection of fusion bonded polythylene. A bottom tow technique was used for installation of the outfall with the required negative buoyancy being provided by 120 ram thickness of concrete weight coating. The outfall was prefabricated in a single length before commencement of the! tow to reduce the required towing time. Long term stability of the outfall is provided using backfilling and rock armour.

DS Barkley

Papers

Design and Construction of Black Rock Ocean Outfall Pipeline