Dam operator concedes there was no 'plant'

Besieged Wivenhoe Dam operator Seqwater has withdrawn allegations against Maurice Blackburn Lawyers, after earlier claiming their private investigator posed as a flood inquiry official to extract information from dam officials.

Maurice Blackburn is investigating a potential billion dollar class action against the government over last year's floods and Seqwater went on the attack on Wednesday before being forced into an embarrassing backdown.

Seqwater, which operates Wivenhoe and Somerset dams, wrote a stern letter to Maurice Blackburn on Wednesday alleging their private investigator Bob Munt had misrepresented himself as being from the flood Commission.

Mr Munt conducted taped interviews with area coordinator Rohan Thorogood and dam operator Anthony Dagan.

However, Seqwater alleged that Mr Munt only got that access because he misrepresented himself.

The letter went on to explain that the Commission asked that day for a statement from Mr Dagan and it appeared Mr Munt may have tried to capitalise on that.

"The conduct of the individual from your firm is unacceptable," the letter widely circulated by Seqwater said.

Commissioner Justice Cate Holmes was concerned by the letter and raised the issue in the inquiry on Wednesday afternoon.

Darryl Rangiah, SC, instructed by Maurice Blackburn and representing Fernvale residents, told the inquiry the law firm did engage Mr Munt to locate and interview Mr Dagan, and that happened on Tuesday as stated.

But everything was above board.

"Mr Munt did not say or represent in any way that he was from or associated with the commission ... and clearly said he was an investigator from Maurice Blackburn," Mr Rangiah told the inquiry.

Maurice Blackburn produced tapes of the interviews to the inquiry that supported their case.

They have now requested an apology.

Just seconds before the inquiry wrapped up for the day Brian O'Donnell, QC, for Seqwater, said after listening to the tapes the organisation now "withdraws the allegations".

A Seqwater spokesperson told AAP that it maintains the conduct was inappropriate but didn't explain why.

Seqwater is under fire in the Commission of Inquiry over claims four dam operators did not move into the correct water release strategy when they said they did and colluded to make a fictitious final report.

The chief executive of the SEQ Water Grid Barry Dennien, who is in charge of water supply, told the inquiry on Wednesday that he only read the final report a few weeks ago, once alleged discrepancies were reported in the media.

He said he trusted the commission to get to the bottom of inconsistencies.

Another of Queensland's top water bosses, SEQ Water Grid director of operations Dan Spiller, earlier said he took only a cursory look at the report.

"My recollection (is) I read it on a bus trip home," he told the inquiry on Wednesday.

Meanwhile, the inquiry will sit for an extra day on Saturday after Mr O'Donnell complained that barristers "in the trenches" responsible for cross-examining witnesses are often given material by the counsels assisting the commission in the evenings or before proceedings that day.

He said in any event they would struggle to get through the remaining 20 witnesses.

"We are struggling to cope with properly preparing for each next day as it is," he said.

Martin Burns, SC, who represents dam engineer Terrance Malone, seconded Mr O'Donnell's plea.

Ms Holmes agreed to the request.

The inquiry is already struggling to meet its reporting date of March 16.

The nine days of planned hearings had already been extended to 11 and now again to 12.

The timing of the Commission's final report into the floods is critical to the Queensland election, to be held on March 24.

Premier Anna Bligh has said she wants Queenslanders to have the findings so they know the truth before voting.

Water utilities minister Stephen Robertson is due to give evidence on Thursday.