Plan to raise Wivenhoe Dam walls among 50 safety options

UPDATE: A PLAN to raise Wivenhoe Dam walls by four meters to protect homes and businesses downstream has been put forward as part of the dam's safety upgrades.

It's one of 50 options being considered under a new study to assure the dam's capacity for very extreme floods and the flood mitigation benefits for past floods.

The safety-centred upgrade will increase the dam's spillway capacity while other options involve retaining the current height of the dam and only increasing the spillway capacity.

Different heights of dam raising will be considered, including no raising of the dam while different spillway options will also be considered, an Seqweater spokesperson said.

Prefered options will be short-listed and identified for government consideration.

The plan is part of Seqwater's staged capital upgrade program delivered over the next 18 years.

While all Seqwater dams comply with the Queensland Dam Safety Regulator, the upgrades are planned to ensure the safety of thousands of homes and businesses downstream.

Minister for Water Supply Mark Bailey said a new study was underway to upgrade Wivenhoe and Somerset dams which included considering options to improve the flood mitigation.

"Over the years we have seen advances in dam design and better understanding of the impacts of climate change, including extreme rainfall events and flooding and this has meant that many dams across Australia need upgrades to address this," he said.

"The timing and cost of the Wivenhoe and Somerset dam upgrades will be determined by the outcome of the current study.

Costs have not yet been determined and will be estimated as part of the studies that are underway but previous estimates reported in the 2014 study ranged from $325 to $880 million.

Mr Bailey said under state dam safety legislation, all dam owners across Queensland needed to manage dams to meet the requirements of the Queensland dam safety regulatory framework, overseen by Department of Energy and Water Supply.
 

UPDATE:  NEW options to improve flood mitigation at Wivenhoe Dam will improve community safety for 300,000 people down stream.

Seqwater is delivering a staged capital upgrade program over the next 18 years, including Wivenhoe and Somerset Dams, which will enable the region's dams to continue to operate safely in the future.

It is understood the safety-centred upgrade at Wivenhoe will increase the dam's capacity by close to a million mega litres and the wall will be raised by four metres. It's expected to cost $900 million.

The schedule of Seqwater's Dam Improvement Program to be completed by 2035 has been determined by the Queensland Dam Safety Regulator, based on risk assessments.

Minister for Water Supply Mark Bailey said all Seqwater dams complied with the requirements of the Queensland Dam Safety Regulator and continued to operate safely but upgrades were needed for the future.

"As part of the program, a new study is underway to upgrade Wivenhoe and Somerset dams which includes considering options to improve the flood mitigation offered by both dams," he said.

"Dams are long-life assets and some of south east Queensland's dams were built in the middle of last century.

"Over the years we have seen advances in dam design and better understanding of the impacts of climate change, including extreme rainfall events and flooding and this has meant that many dams across Australia need upgrades to address this.

"The timing and cost of the Wivenhoe and Somerset dam upgrades will be determined by the outcome of the current study.

"Risk assessments and safety measures undertaken by Seqwater to date have been endorsed by the dam safety regulator and reviewed by independent dam experts.

"Dams are large public infrastructure and maintaining their ongoing safety is paramount.''

Mr Bailey said that under state dam safety legislation, all dam owners across Queensland, including Seqwater, needed to manage dams to meet the requirements of the Queensland dam safety regulatory framework, overseen by Department of Energy and Water Supply (DEWS).

"Under the Queensland dam safety guidelines Seqwater is required to progressively complete its dam upgrades by 1 October 2035. However, the outcomes of the current study could see works being undertaken on Somerset Dam as early as 2022 and Wivenhoe as early as 2025," he said.

Seqwater acting chief executive officer Jim Pruss said all of SEQ's dams operated safely and the program of planned works would enable this to continue in the future.

"Seqwater recognises the upgrades to Wivenhoe and Somerset, in particular, will be of significant interest to the community,'' Mr Pruss said.

"We are in the initial planning phase. Later this year, once the planning scope is finalised, we will be providing the community with details of the upgrade study, its timeframes, as well as regular updates as the program progresses.

"Seqwater is prioritising its Dam Improvement Program to deliver a staged capital program that safeguards the community and delivers best value for money.''

In recent years Seqwater has upgraded a range of dams across SEQ including Lake Manchester (2008), Borumba (2008), Hinze (2011), North Pine and Ewen Maddock Stage One (2012), Maroon and Moogerah (2014).

INITIAL: A PLAN to raise Wivenhoe Dam walls by four meters to protect homes and businesses downstream has been canvassed as part of the dam's upgrades.

The safety-centred upgrade will increase the dam's capacity by close to a million mega litres, up from the current flood mitigation capacity of more than two million mega litres.

The plan is expected to cost up to $900 million and forms part of existing upgrade works.

It's expected to be finished by 2030.

A study shows a dam failure could put close to 300,000 people in danger and had the potential to kill 400.

Wivenhoe Dam has a total storage capacity of 3.132 million mega litres.

During a flood, Wivenhoe is designed to hold back a further 1.967 million mega litres on top of its normal storage capacity.


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