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Detailed design proceeds for Dungowan dam

The proposed project will involve the existing dam being replaced with a larger structure, increasing the water storage capacity from 6.3 to 22 Gl.

WaterNSW, the bulk water supplier for Australia’s southeastern state of New South Wales, has hired SMEC to deliver the detailed design for the new Dungowan dam, following the consultant’s successful delivery of the concept design in early 2021.

The detailed design will include further geotechnical investigations, embankment and spillway design, outlet works design (structural and hydro mechanical), decommissioning of the existing Dungowan dam, as well as ancillary works, including road design and utility supplies, the company announced at the end of Oct­ober.

The new 58 m-high earth and rockfill dam is to be located around 3.5 km downstream of the existing dam on Dungowan Creek near Tamworth in northwest New South Wales, which will be decommissioned. A new 55 km-long pipeline will also be built to supply water from the dam to the Calala water treatment plant, replacing an existing pipeline, which supplies water to Tamworth.

This project has been designed to ensure long-term water supply security for Tamworth and other townships in the Peel Valley, as well as help strengthen drought resilience and improve water reliability for local industry and agricultural production.

The construction of a larger dam would also improve the ability to store a greater volume of inflows, including from tributaries down­­stream of the existing Dungowan dam.

In addition, the temporary storage of flood inflows facilitated by the larger dam will contribute to the reduction of the impact of flooding on the downstream community, particularly during larger, less frequent flood events.

Furthermore, the risk of failure of the existing Dungowan dam, which has identified safety issues, will be significantly reduced.

The new spillway is being de­signed to pass a substantially higher flood. The current dam, which has been listed as a ‘High B’ Con­sequence Category Dam, does not meet the current safety requirements of the NSW Dam Safety Com­mittee.