The Sydney Catchment Authority confirmed that the test was accurate, but said the water gets safer to drink in the lower river, approaching Warragamba Dam.
Approximately 30 minutes from the city of Penrith, New South Wales, Silverdale is close to the historic township of Warragamba, and the main water supply for Sydney, Warragamba Dam.
In 1845, Paweł Strzelecki drew attention to Warragamba River as a water supply catchment; and in 1867, supporters proposed a dam.