SunWater was appointed by the Gold Coast City Council to assist with the selection and establishment of an alliance team to deliver the raising of Hinze Dam to Stage 3 to meet flood migration, dam safety and water supply objectives. The appointment was extended to enable SunWater to provide a peer review role of the selected alliance team’s design during the turnout cost phase of the project.

The Hinze Dam Stage 3 (HDS3) project will see the dam wall raised from 93.5 metres to approximately 108.5 metres, and will:

• Reduce the flooding in the lower Nerang River catchment
• Increase water supply from Hinze Dam to 225 million litres per day
• Ensure the dam complies with current and future safety standards and guidelines

The selected alliance team comprises Thiess Pty Ltd, Sinclair Knight Merz, URS, Gold Coast City Council, with SunWater providing technical advice to the council as the owner’s engineer.

The Hinze Dam Alliance brings specialist private sector expertise to work with Gold Coast City Council's Economic Development and Major Projects Directorate and Gold Coast Water in the delivery of this project.

Pre-construction activities commenced in October 2007 and the construction work commenced in January 2008.

Hinze Dam Physical Hydraulic Modelling

SunWater was also responsible for the construction and testing of a physical hydraulic model of the proposed spillway arrangement as part of the Hinze Dam Stage 3 upgrade. The model provides crucial information for the design of the upgrade; such as water surface levels, discharge ratings, pressures, velocities, and ensuring acceptable hydraulic conditions exist.

The model was built to a scale of 1:50 and included a large portion of the reservoir, the spillway, the energy dissipater, The Stage 1 spillway and chute, and the downstream channel. The model has a fixed bed with the upstream topography around the dam reproduced from cement mortar over compacted sand filling between accurately shaped masonite templates.

The spillway was constructed from thick perspex chosen for its hydraulically smooth surface and dimensional stability. The pressures along the spillway chute are measured using piezometer pressure tapings connected to manometer tubes. Velocities were measured with miniature meter and pressure transducers were installed to measure transient pressures.

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