Dam Upgrade Project Update

In September 2022, our early contract involvement procurement process identified design changes and escalating labour and material costs have led to a significant increase in the expected cost to complete the upgrade. As a result, we now need to explore how we can refine our design for the new dam wall to meet the objectives of this project in a way that is financially prudent.

We will first undertake a comprehensive review of all previous design options. Once this process is finalised, we will develop a new procurement strategy – involving our previous tenderers – which will take the project through to completion.

This approach provides our project team with more scope to develop an optimal design that ensures Mount Bold’s dam remains in step with modern standards.

Based on this review process, early construction work is expected to commence in 2028, with the upgrade planned for completion in 2034.

The Mount Bold Dam remains safes, with no known defects that cause any concerns under normal operating circumstances.

We perform leading-practice daily, annual and five-yearly proactive inspections to comprehensively assess the dam’s condition, confirming the structure remains in sound condition.

Our approach to enhancing dam safety across our portfolio has been based on risk, with Mount Bold Dam having a lower risk compared to other dam’s we’ve already upgraded.

Background

Mount Bold is an important storage for both natural inflow and water pumped from the River Murray, with a total capacity of around 46 billion litres. It was constructed between 1932 and 1938 and is approximately 25 kilometres south-east of Adelaide, within the Onkaparinga catchment in the southern Mount Lofty Ranges.

Our state’s largest dam was identified for upgrade as part of standard process and responsibility to maintain our structures and assets in safe operating condition. We perform regular and extensive safety checks of the infrastructure, including annual engineering assessments. The dam remains safe on a day-to-day basis and there is no imminent risk of failure.

The dam safety project will align Mount Bold with the Australian National Committee on Large Dams’ (ANCOLD) updated guidelines that we follow to ensure best practice in the operation of our dams and reservoirs. The upgrade of Mount Bold will strengthen the dam structure against earthquakes and its capacity to safely pass any large flood events, while also providing improved flood protection to the downstream community.

Planning for this significant project continues, including hydrology and geotechnical studies, flood modelling and development of options assessment.

Environmental impacts

Initial flora and fauna assessments have been undertaken to fully understand the complete and seasonable existence of species surrounding the construction footprint of the dam upgrade based on early concept designs.

Further surveys and assessments will be undertaken as part of environmental and planning approvals required for the project. We will also assess and balance environmental, cost and constructability requirements and implement strategies to minimise impacts including utilising existing footprints, revegetation planning and investigation of the use of a mini-hydro at the dam to offset energy costs.

Community involvement

We have been working with government agencies including the Department for Environment and Water (DEW), the Stormwater Management Authority (SMA) and local council to explore the additional flood attenuation design option and to source external funding required to deliver this option.

Engagement with key stakeholders has involved establishment of a community reference group in May 2020. We will continue engagement and consultation with the broader community as planning progresses through the concept, detailed design and construction phases of the project.