By the 1820s the Tank Stream, Sydney’s main supply of fresh water, was insufficient and polluted.
In 1824, Governor Darling appointed 59 year-old engineer John Busby, as Government Mineral Surveyor. Busby was appointed to locate another water source. The eastern portion of Sydney Common contained an area known as the Lachlan Swamps, with natural aquifers in the Botany Sands geological system, which were an ideal source of water. The Lachlan Water Reserve was established within the Common.
Busby reported that Lachlan Swamps’ was a low-lying marsh with a plentiful supply of fresh clean water "free from every taste and smell, and so soft as to be fit for every purpose". Busby determined that the water could be conveyed to the city through an underground tunnel or ‘bore’, for distribution at what is now Hyde Park.
Hopes were high for the colony to have its new clean water supply within a few years, but this was not to be.
In 1827 construction of the Lachlan Water Tunnel (Busby’s Bore) commenced with convict labour under Busby’s direction, to provide a supply of fresh water to a terminal in Hyde Park. Twenty-eight shafts were excavated along the line of the tunnel.
Difficulties with the rock strata and the use of unskilled workers caused problems for the project – it took ten years to complete.
Lachlan Swamps served as Sydney’s main water supply from 1837 to 1859 when a combination of the growth of industry, poor maintenance, livestock grazing, and garbage dumping gradually polluted the swamps.
Pollution worsened considerably in 1874 after a spate of large floods, and even though seven new dams were built to resolve the problems, they continued.