Woronora Dam

Woronora Dam collects water from the catchment of the Woronora River, which drains into the dam and then to Georges River. The dam supplies water to residents within the Sutherland Shire in Sydney's south and also the northern Illawarra suburbs of Helensburgh, Otford, Stanwell Tops, Stanwell Park and Coalcliff.

Proposal and justification

Water was first supplied to Sutherland Shire in 1911 when a 150mm pipe was laid from Penshurst Reservoir across Georges River at Tom Ugly's Point to Miranda.

In 1920 a scheme to supply water from the Woronora River to Sutherland and Cronulla was rejected. It was resurrected five years later when the then Metropolitan Water Sewerage and Drainage Board became the sole constructing authority for water supply works in the metropolitan area.

The scheme involved the construction of a dam, which could be increased in size if necessary, on the Woronora River about 24km upstream of its junction with the Georges River.

Constructing Woronora Dam

Construction of the dam began in 1927, but as forecast, its size had to be increased two years later.

Workers' accommodation was spartan but functional with small bungalows built of fibrolite and placed on brick or concrete piers on the sloping ground. In 1930 The Depression intervened, suspending work on the dam. The men were forced to look for work further afield, even interstate, often leaving their families behind to live on the Woronora site.

Some families had strong ties to the history of Sydney's dams, moving from the Nepean Dam project to Woronora and then onto Warragamba. Other workers on Woronora Dam were former coal miners from nearby Helensburgh.

Late in 1931 the Unemployment Relief Account released funds to build a weir to provide water to the Sutherland-Cronulla area and four years later, work resumed on the dam itself.

Woronora Dam was completed in 1941 at a cost of about $13 million. Six of the cottages were retained for on-site maintenance staff housing while the rest of Woronora township site was turned into picnic and recreational areas.

Features of Woronora Dam

Woronora Dam is curved in appearance and is a mass gravity dam, remaining in position under its own weight. Its lower levels are built of cyclopean masonry - massive sandstone blocks that were quarried on site. The main wall is made from blue metal and gravel concrete and there are two inspection galleries located inside.

The dam has a separate, serpentine spillway that discharges floodwater through a concrete lined cutting into the river downstream of the dam.

In 1988 Woronora Dam was upgraded at a cost of $2.9m by a system of wall and foundation drains to meet international dam safety standards.

Raw water from Woronora Dam is pumped to the adjacent Woronora Water Filtration Plant. This plant is one of nine in Sydney either operated by Sydney Water or privately owned and operated under contract to Sydney Water. The dam and water filtration plant supply water to the areas south of the Georges River including Sutherland, Helensburgh, Stanwell Park, Lucas Heights and Bundeena.

*Height: 66 metres
*Length: 390 metres
*Capacity: 71,790 megalitres
*Catchment area: 75 square kilometres
*Lake: 4 square kilometres

The Maritime Operations Division within the Department of Defence uses Woronora Dam to test its sonar facilities. The testing station is on a pontoon in the middle of the reservoir. The building of the Woronora Dam became part of the backdrop of the comedy drama "Dad Rudd MP". The film features several construction scenes and employed many workers and their families as 'extras'.

The dam can be viewed by the public, and has a walking trail across the dam wall, and a picnic area including a carpark. Woronora Dam Road leads from the Princes Highway for seven kilometers to the dam.

References

*Sydney Catchment Authority. [http://www.sca.nsw.gov.au/dams/woronora.html Woronora Dam]
*The Water Supply, Sewerage and Drainage of Sydney, W.V.Aird, 1961, MWS&DB.