Engineer says defective Paradise Dam ‘probably stable’

An engineer who worked on Queensland’s defective Paradise Dam has disputed a report that the structure is unsafe.

The Paradise Dam. Picture: Peter McNamara

A world-renowned engineer who worked on Queensland’s defective Paradise Dam has disputed the findings of an independent ­report that the structure is unsafe as other dam experts called for more testing ahead of repair work set to begin in April.

American dam engineer Ernest Schrader was among five ­experts giving evidence on Tuesday at the commission of inquiry into the 300,000 megalitre dam, deemed at risk of failing in the event of a major flood.

Three of the five called for more testing to determine the extent of problems with the roller-compacted concrete gravity dam — the biggest of its type in Australia when it opened in 2005 — about 80km from Bundaberg.

Testing of the dam in 2006 and after it suffered damage in the 2013 flood showed extensive problems with the bonding of the concrete layers in the dam wall.

Described at the opening of the inquiry as playing a central role in the dam’s design and construction, Dr Schrader told the hearing he “wasn’t the designer of this particular dam’’.

He offered new evidence at the end of Tuesday’s hearings that during construction, the presence of ground water had proved a problem in the laying of concrete and at one stage “precast panels’’ had “pulled off the structure”.

He said the issues could only have been caused by water but he did not document the problem.

“I don’t believe I documented it, I don’t think it was documented,’’ he told the hearing.

Last year, it was revealed that technical investigation into the dam had been hampered by the absence of documents, including the critical construction report.

Asked whether he agreed with the findings of consultant GHD’s 2019 report that the dam was unsafe in the event of a flood, Dr Schrader said he believed mistakes had been made with parts of the assessment. “In my opinion and knowledge, (the dam) is most probably almost certainly stable but it hasn’t been demonstrated by test results that it is,’’ he said.

The $200m dam was built under the Beattie government by the Burnett Dam Alliance.

Global geotechnical expert Paul Rizzo, who has been engaged by local growers, and US-based concrete materials engin­eer Steve Tatro said they believed further testing was needed but civil engineer Timothy Dolen told the inquiry further tests could delay repair work at the ­expense of safety.

“I think the tests give sufficient reliability to support the stability assessment,’’ he said.

The problems with the dam led to the lowering of its water storage levels and the spillway for repair work that may not be completed until 2026.

Water Minister Anthony Lynham has refused to commit the government to ­restoring the full capacity of the dam, despite pleas by the local council and agriculture groups.