The Western Treatment Plant (formerly the Metropolitan Sewage Farm or, more commonly, the Werribee Sewage Farm) is a 110 km² (42 sq mi) sewage treatment plant in Cocoroc, Victoria, Australia, 30 km (19 mi) west of Melbourne's central business district, on the coast of Port Phillip Bay. It was completed in 1897 by the Melbourne and Metropolitan Board of Works (MMBW), and is currently operated by Melbourne Water. The plant's land is bordered by the Werribee River to the east, the Princes Freeway to the north, and Avalon Airport to the west. It forms part of the Port Phillip Bay (Western Shoreline) and Bellarine Peninsula Ramsar Site as a wetland of international importance. The Western Treatment Plant treats around fifty percent of Melbourne's sewage — about 485 megalitres or 393 acre-feet per day — and generates almost 40,000 megalitres or 32,000 acre-feet of recycled water a year. (The Eastern Treatment Plant treats 40%.)