Somerset Dam is one of five dams across the region identified for upgrade in the next 5-6 years.

Seqwater is setting an example for water utilities across Australia with its improvement program for South East Queensland dams. The upgrade program aims to increase storage capabilities, improve the ability to handle extreme water management challenges and ensure the dams comply with safety guidelines.

Many of Seqwater’s dams supplying drinking and irrigation water to South East Queensland were built in the 1960s and 1970s, with the oldest dam constructed in 1866.

Seqwater is regulated and its dams aim to meet national guidelines as defined by the Australian National Committee on Large Dams (ANCOLD).

As with any infrastructure, structural deterioration can occur over time, which is why in 2012 and 2013 Seqwater commissioned independent assessments of its 26 regulated dams to determine if they are adhering to the guidelines and if any maintenance works were required.

The assessments also considered how the infrastructure could be improved to handle predicted population growth and future weather events.

From this comprehensive information, Seqwater has created the Dam Improvement Program and is rolling out upgrades to its South East Queensland dams.

Removal of spillway gates at Leslie Harrison Dam.

Removal of spillway gates at Leslie Harrison Dam.

What has been upgraded?

There has been significant advances in dam design, assessment methodologies, extreme rainfall estimates and flood modelling in Australia, all which have been used in the implementation of these upgrades.

Seqwater Asset Portfolio Development and Delivery General Manager, Daniel Spiller, said all 26 of Seqwater’s dams that had been issued with safety conditions by the Queensland Dam Safety Regulator under the Water Supply (Safety and Reliability) Act 2010 were included in the Dam Improvement Program.

“We have a rolling assessment, monitoring, review and maintenance program to meet safety guidelines, and improve our water storage capabilities. The Dam Improvement Program involves upgrading dams identified as a priority and reducing the water levels of some dams until such time as improvements can be made safely,” Mr Spiller said.

While improvements to each dam differs depending on the individual assessments, overall the upgrades may involve increasing spillway capacity, installing sand filter zones to safely manage seepage through the dam embankment, installing post-tensioned anchors to provide greater sliding resistance or raising the height of a dam wall.

Mr Spiller said Seqwater had implemented a range of actions in response to the assessments.

“To date, we have lowered the drinking water storage levels of eight dams – Bill Gunn Dam near Laidley, Cooloolabin Dam on the Sunshine Coast, Leslie Harrison Dam at Capalaba, Sideling Creek Dam (Lake Kurwongbah), North Pine Dams at Petrie, Nindooinbah Dam in the Scenic Rim, and the Wivenhoe and Somerset dams in the Somerset Region.

“In 2014, we also completed the Stage 1 upgrade of Maroon Dam, which included extending the existing grout curtain and pressure relief wells on the abutments to limit seepage and ground pressures during flood events and extending the existing weighting berm,” Mr Spiller said.

Works began in late 2016 to modify the embankment and spillways, and install new filter drains at Wappa Dam, as well as the commencement of a minor upgrade to Somerset Dam involving the construction of a parapet or wave wall on the dam’s breezeway to increase its flood mitigation capacity.

Upgrades to Ewen Maddock Stage 2, Lake Macdonald Dam, Sideling Creek Dam, Somerset Dam and Leslie Harrison Dam are also predicted to take place over the next five years.

Geotechnical investigations at Somerset Dam.

Geotechnical investigations at Somerset Dam.

Dam maintenance nation-wide

While Seqwater’s upgrade program is confined to its South East Queensland dams, Mr Spiller said the knowledge learnt through the assessments and monitoring of these dams could be applied on a national level.

“South East Queensland is one of Australia’s fastest growing regions and the demand for water is increasing. It is Seqwater’s intention to share our learnings and collaborate with other water industry professionals and organisations to offer new insights into sustainable water management.”

Mr Spiller said water utilities around Australia should also take note of advances in hydraulic modelling and data collection that was used to evaluate downstream areas because these helped provide accurate data on the water flows over the floodplain in Seqwater’s assessments.

“In South East Queensland, we live in a climate of extremes – from times of drought to floods – and we need to be ready to adjust our water use and management when conditions change.

“We have undertaken extensive hydrological modelling to allow the dams to be assessed for rare to extreme floods and this work has been used in the Queensland Government Wivenhoe and Somerset dams optimisation study.”

Mr Spiller said other cutting edge ground investigation techniques had also been used to gather data on the foundations and material within dam embankments, information which would be of use to the wider industry. This has included the use of acoustic televiewer instruments in bore holes, cone penetrometer testing and seismic refraction surveys.

“Research, collaboration and knowledge-sharing within the water industry is essential to understanding and solving the water challenges of today and tomorrow,” Mr Spiller said.

Jessica Dickers is an experienced journalist, editor and content creator who is currently the Editor of Utility’s sister publication, Infrastructure. With a strong writing background, Jessica has experience in journalism, editing, print production, content marketing, event program creation, PR and editorial management. Her favourite part of her role as editor is collaborating with the sector to put together the best industry-leading content for the audience.

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