to finishes and planning of all four of the Metropolitan Dams. The means of delivering stores and raw material through the network of railway lines and raised platforms, and the system of suspension footbridge and aerial stone ropeway to provide access and material over the gorge were particularly sophisticated for the time and foretells later developments at Warragamba Dam. The reservoir of the Nepean Dam is the second largest source of water in the whole of the network administered by SCA for the supply of metropolitan Sydney. The place is important in demonstrating the principal characteristics of a class of cultural or natural places/environments in New South Wales. Nepean Dam is representative of a type of dam (cyclopean masonry gravity dam) constructed in NSW by the Water Supply and Sewerage Branch of the Public Works Department during the first half of the twentieth century. Key representative e attributes of the dam's design and construction include the use of cyclopean masonry bedded in sandstone concrete, use of blue metal concrete in the wall facings, use of a spillway set away from the gravity wall, valve and crest houses attractively designed and finished to a high standard, the use of an array of upstream intakes to regulate the quality of water supply, the internal inspection gallery, the foundation drainage system, the contraction joints, and the internal drainage system. The upgrading works to the spillway and dam wall in the 1980s, with the rock embankment to make the dam meet modern safety requirements are representative of modern-day safe operating practice. The construction technologies used at Nepean Dam are representative of dams constructed in NSW through the first half of the twentieth century. Key representative attributes include the use of cableways, the building of temporary camps to house labourers and tradesman, building of semi-permanent cottages to house salaried staff, the construction of terraced platforms for plant and machinery, mechanisation of concrete production, the construction of a purpose-built road of access and tramway to transport men, supplies and materials from the nearest railhead to the construction site, the building of permanent infrastructure such as water supply for plant and men and horses, and the use of electricity to power plant and equipment. The rehabilitation of tracts of land scarred in the construction process employed at Nepean Dam through beautification works is representative of practices undertaken at other dams throughout NSW. Key representative attributes of this