In the 1860s following droughts and population expansion, the need for a larger and more reliable water source was required for Sydney. A Special Commission, in 1869, recommended construction of the Upper Nepean Scheme. The proposal was approved in 1877 and work commenced in 1880. The canal was originally a dry-stone masonry construction in 1888. From 1902-12 it was largely reconstructed and relined to decrease outflow and increase capacity and stability. A part of the canal known as the Covered Way, located at the base of Prospect Hill near Hyland Road Greystanes, collapsed in 1904 and was reconstructed in 1905. The Covered Way is a basined component of the canal that protected the water supply from contamination that may have entered the canal due to the steepness and proximity of Prospect Hill.