Wall strengthened by installation of post-tensioned anchors. The original Larner Johnson Needle Valve has been replaced with an AGE Ring Faulkner Valve. Spillway and dam upgraded for dam safety purposes in 1981 and 1989. Further information Cataract Dam is located in Wollondilly and Wollongong LGAs. Heritage listing As at 21 January 2009, Cataract Dam was the first of the four water supply dams built as part of the development of the Upper Nepean Water Supply Scheme, one of the most important engineering works and items of public infrastructure in Australia. Cataract Dam was designed by engineers of the Public Works Department under direction of two of Australia's leading water supply engineers, L.A.B. Wade, Chief Engineer for Water Supply and Sewerage and E.M. De Burgh, who was Supervising Engineer. The completion of Cataract Dam was a significant step in the continuing process of providing a reliable water supply for Sydney and surrounding areas and was part of a process of development of the Upper Nepean Scheme which was envisaged when that Scheme was designed in the 1880s. Cataract Dam was the largest dam constructed in NSW at the time and was considered to be a significant work of engineering in its day. It continues to play an important role as a major source of water supply for the Sydney area. Additionally, the Cataract Dam is a handsome, well proportioned structure with strong Tudor style architectural character which complements the monumental nature of the structure and its attractive natural surroundings. Cataract Dam includes a range of ancillary structures which form components of the overall site, including a set of handsome sandstone masonry residential cottages for operational staff (which appear to date from the construction of the dam). They are representative of their age and type. The Official Quarters is a particularly fine example of a Federation Queen Anne Bungalow, with matching outbuildings and landscaped gardens and is associated with the accommodation of both the senior engineers of the Public Works Department and the Governor of NSW at the opening of the Dam. The Residential Engineers Cottage is also a fine quality building dating from the 1960s. The Dam surrounds include remnants of its early 20th century gardens, evidence of a high level of landscape design awareness through its planning and detailing, and extensive areas of bushland. Individual components of its remnant gardens, such as its main (upper level) grotto shelter and ornamental