A new report on the operation of the Wivenhoe Dam during last year’s Brisbane floods has cleared the engineers involved, despite earlier findings by the Queensland Floods Commission of Inquiry that they were in breach of the dam operating manual and gave contradictory evidence.

The US Bureau of Reclamation and the US Army Corps of Engineers were commissioned by the Queensland Government to review dam operator Seqwater’s report on the January 2011 deluge.

They say operational decisions made were “prudent” and taken “with appropriate engineering judgement given the available information”.

This supports the Crime and Misconduct Commission decision in August to clear the three engineers. A judge found the “conflicting” and “badly drafted” dam manual led to confusion about when different flood strategies were in place.

The earlier floods commission findings have driven a class action by about 4000 people in a “no-win, no-pay” case involving lawyers Maurice Blackburn.

Maurice Blackburn Principal Damian Scattini says he does not consider the US report comprehensive.

“The reviewers relied heavily on the Seqwater event report, which was strongly criticised by the Queensland Floods Commission of Inquiry as being inaccurate,” he told insuranceNEWS.com.au.

“Further, it does not appear that the reviewers gave any consideration to the final report of the inquiry, which found the flood operations engineers had breached the manual during the floods.”

Mr Scattini says the law firm’s own investigations are ongoing. “All current indications are that the inquiry’s findings as to mismanagement are correct and that the mismanagement made a major contribution to flooding downstream of Wivenhoe.”

Seqwater has backed its engineers. CEO Peter Borrows says the company is “confident its position will be justified if the matter ever comes before a court”.

He says the water utility “does not waver from its belief that its engineers did an extraordinary job in the most difficult and demanding circumstances” and the dam was “managed appropriately” during the flood.

“It was the largest flood inflows that southeast Queensland had experienced in more than 100 years,” Mr Borrows said.