a water supply dam are a lasting testament to the professional capabilities of the late Victorian/Edwardian era generation of engineers of the Public Works Department. Description Cordeaux Dam is a cyclopean masonry dam composed of sandstone blocks, weighing from two to four and a half tons, quarried at the site and bedded in a cement mortar. The roughly rectangular blocks were bedded on and packed with sandstone concrete, with cement mortar only being used where considered necessary. The concrete is made with crushed Hawkesbury sandstone. Concrete made of hard basaltic stone (instead of the softer sandstone) is used for the upstream face, thick, which merges into sandstone concrete thick at lower levels and thick at higher levels. The dam wall is curved in plan and has a bywash spillway as a continuation of its southern end. Each end of the dam wall is flanked by massive Egyptian style pylons complete with decorative lotus columns. These pylons differ from those at Avon Dam by having heavy fluting to the lotus columns. Two valve houses along the dam wall are square, flat-roofed concrete buildings with strong Egyptian stylisation in the tapered wall profiles, circular beading to corners and overhanging eaves. These contain discharge outlets, with the Upper Outlet consisting of two pipes with FCD valves and Ring Faulkner gate valves. The two lower valve houses at the downstream foot of the dam wall are very similar in appearance and which contain discharge pipes with Ring Faulkner gate valves and scour valves as outlets. The dam featured a number of improvements in design and construction on the earlier-completed Cataract Dam. These included contraction joints between units of construction placed at intervals of ; inspection galleries at upper and lower levels, together with piping for registering any ground water pressure. Specifications for Cordeaux Dam: Total capacity: . Greatest depth of water: . Greatest height of wall: (above foundations). Length of crest including pylons: . Area of lake: (when full). Top water level . Completed in 1926. Cost: A£945,000 ($1,908,000). Concrete in wall: . Length of spillway weir: . Width of crest: . Width of base: . Cordeaux Dam storage is discharged to the Cordeaux River downstream, flowing to Pheasants Nest Weir on the Nepean River where it is diverted through a tunnel long to the Cataract River at Broughton's Pass. From here it is diverted by another weir to the Cataract Tunnel, long, emerging