WARRAGAMBA DAM RAISING DESIGN
Warragamba Dam is a water supply dam located 65 km from the city of Sydney, Australia. It supplies water to more than 5 million people in Sydney and the lower Blue Mountains.
The raising of Warragamba Dam was being considered as a means of providing flood mitigation for the Hawkesbury-Nepean Valley downstream of the dam. Mitigation consists of attenuating flood peak flow and providing additional time for emergency response and the evacuation of areas where flooding presents a risk to life and property. The population downstream of the dam that is exposed in the event of a flood is approximately 100,000 people.
Stantec was engaged to develop a detailed concept design to be the basis for developing a cost estimate and business case to be considered by the NSW State Government. The initial construction costs were estimated to be approximately AUD $ 1.5 billion.
The existing dam is 142 m high by 351 m long with the capacity to pass a flow of up to 45,000 m3/s of water during extreme flooding. The raising of the dam requires strengthening the dam structure to retain water to a higher level and upgrading hydraulic structures to safely pass inflows during a flood.
The project is on-going, and a decision is yet to be made by the New South Wales Government if it will proceed.
I worked full-time on the project for almost two years, and it was the first major civil infrastructure project I was involved with. The nature and scale of the project attracted international experts across our company to complete the design and across the dams field to review our work.
The team assembled was a diverse one in professional experience and background. It was not always smooth collaboration amongst the team. Early on there were personality clashes and working across different geographies took adjusting. However, those issues were worked through with time and eventually lead to positive outcomes. It became a closely connected group and a great learning environment for me.
My work on the project included the following:
• Completed hydraulic design of raised spillways, gated conduits, aerators and dissipators.
• Performed flood routing calculations for optimization of spillway crest levels, flood mitigation zone drawdown and construction sequencing.
• Completed a tailwater study using HEC-RAS and MIKE11 river models.
• Wrote a report on the temporary works required during construction and construction methodology.
• Calculated construction quantities for the initial concept design.
• Reviewed and optimised operational rules for drawdown of new flood mitigation zone by developing Visual Basic program to model operation during flood events.
• Supported stability analysis and 3D finite element analysis through Excel spreadsheet calculation tools, review of historical data records and analysis of computational fluid modelling results.
• Helped prepare final detailed concept design report and deliverable documents through writing, editing and formatting.
• Assisted project director through management of project controls, documentation and correspondence.
When I started the project, I had no prior experience in dams. The journey of learning new technical concepts took the full two years. I had to build the confidence to discuss them, to write about them and to present them to experts. At the end of that period, I felt I was capable of delivering technical work at a true professional level.