2006 – Accessing Deep Storage at Warragamba Dam

B Simmons, N Mudge

In 2004 the NSW Government released its Metropolitan Water Plan (MWP). This plan detailed the government’s initiatives to secure Sydney’s water needs during the current drought and into the future. The MWP outlined a range of both demand and supply side measures. These included modification to Warragamba and Nepean dams so that the water at the bottom of the dams that is currently unavailable for water supply can be accessed.

Accessing this deep water will increase the available water supply by an additional six months in the immediate drought and will provide, on average, an additional 40GL/annum to our long term available water supply.

The Warragamba Dam Deep Water Access Project involves accessing and transferring water from deep in Warragamba Dam to the existing water supply system.

Phase One of the project saw an abandoned underground pumping station 1.5km downstream of the dam wall, being enlarged and upgraded to pump water from the low level pipeline into the existing water transfer pipelines.

Phase Two of the project involved making a penetration low on the dam wall, some ninety metres below full storage level to access the deep water. This enabled the water to flow into the new pumping station, through an existing underground pipeline.

This project and in particular Phase Two was extremely unique due to the saturation diving systems and specialist tooling systems needed to create the penetration in the dam wall. The project provides a reference point for the water industry for future similar works.

This paper describes the project that was initiated at Warragamba Dam to access the deep water and is focused on the extremely difficult and unique works associated with creating the low level penetration in the dam wall.