Deep storage

The Sydney Catchment Authority (SCA) has major projects to implement as part of the NSW Government's Metropolitan Water Plan.

One of these involves modifying existing and installing supplementary infrastructure to access 'deep water storage' at Warragamba and Nepean Dams.

Deep water storage is water which lies below the lowest outlet point in a dam from where water can be extracted, or below the level where gravity can draw the water out of the dam.

Combined, the deep storage projects at Warragamba and Nepean Dams add around six months of water supply to the system for use in the present drought. They also increase the amount of water we can draw out of the dams each year by about 40 billion litres.

The deep water pumps are already working at Nepean Dam securing the water supply for 270,000 residents in the Illawarra and the pumps at Warragamba are ready to start pumping if the level of the dam falls to around 19 percent.

Warragamba deep water project wins Engineering Excellence Award

The Warragamba Dam Deep Water Access project has won the Infrastructure Project category at the 2007 Engineering Excellence Awards (Sydney Division) held on 21 September 2007.

The award recognizes the project as a major engineering achievement. It is highly innovative in providing an environmentally sustainable and very cost effective solution within a very tight project timeframe while overcoming a number of unique engineering design and construction challenges.

The project’s success was achieved through the integrated team approach adopted by the SCA, the Department of Commerce (project manager) and Baulderstone Hornibrook (construction contractor).

To access deep water at Warragamba Dam, a disused pumping station 1,500 metres downstream of the dam was refurbished. This pumping station will lift the water from the low level outlet at Warragamba Dam into the existing Warragamba pipeline, which flows to Prospect Reservoir.

The most technically challenging part of the project was creating access to the low level outlet to allow the water to flow through to the pumping station. To reach the outlet, a team of specialist saturation divers used a specially designed cutting rig to cut and remove a 17 tonne concrete block, providing a two by two metre opening. This work was carried out at a depth of approximately 85 metres below the water level.

A display of the Warragamba Deep Water Access Project (and other category winners) will be erected at the Powerhouse Museum from late 2007 to October 2008.

The project is also now an entrant in the National Engineering Excellence awards.