Experts asked: Is Paradise Dam stable?
UNITED States dam experts agree more data is needed to determine if Paradise Dam is safe or not.
Five witnesses were cross-examined during the Commission of Inquiry yesterday, and they were asked if the dam was stable based on the information that was available.
Some of the witnesses have published reports which the State Government has relied on in its justification of lowering the dam spillway by at least five metres, due to concerns of its integrity.
GHD'S principal dams engineer James Willey, who wrote two technical reports of the dam for client Sunwater last year, was the only Australian witness in the cross-examination.
"Is it stable under the full range of events that are expected?" Mr Willey said.
"It's presented in the (GHD) stability memoranda, and that indicates that for particularly large and extreme flood events, there's a Factor of Safety less than 1."
Colorado based roller compacted concrete consultant Timothy Dolen said "I agree with Mr Willey."
TatroHinds consultant Steve Tatro, who completed a technical evaluation for Sunwater last November, said by phonecall, "are you asking me if these are all the test results we're going to get, and no further testing is going to be done?
"What do we do? (We're) shooting ourselves in the foot and I guess we're forced to move towards some kind of mediation. I just hate believing we have," Mr Tatro said.
Mr Tatro's report objected to GHD repeating tests of the same core samples taken from the dam, and he said in the commission he did not believe them to be reliable.
United States expert Ernest Schrader, who provided advice during the construction of the dam, said; "In my opinion, with my knowledge of it, I think it's most probably certainly stable, but it hasn't been demonstrated by test results that it is."
Dr Schrader made several recommendations which he said would be simple and affordable, and that if taken could confirm the stability of the dam.
If these measurements were unfavourable then more testing had to be completed, he said.
Dam consultant Paul Rizzo, who is providing advice to Bundaberg Fruit and Vegetable Growers, spoke in a poorly connected phonecall, which at times required him to repeat his points of view to the senior counsel.
Dr Rizzo said further data of the dam was needed, and that a technique such as block testing should be used.
"It's not impractical and not overly expensive," he said.