Up to $20 million will be spent repairing Canberra’s Scrivener Dam after a safety audit uncovered corrosion problems.
The annual safety audit of the dam three weeks ago found corroded bolts in the flap gates of the dam wall which are opened during flooding to regulate the level of Lake Burley Griffin.
It recommended 120 anchor bolts be replaced within one to two years.
“The engineering work involves replacing every bolt, on every hinge, on every gate,” said National Capital Authority (NCA) chief executive Gary Rake.
“Each of the five flap gates will, in turn, be removed and replaced by a temporary floating gate while the bolts are changed.”
Most of the bolts are encased in steel structure or concrete and are difficult to access.
The work will also include redesigning the anchor bolt system to reduce corrosion and improve accessibility.
It is expected to cost between $15 million and $20 million (AUD), and will take up to 18 months to complete.
Mr Rake says the lake level is also being lowered to the same level reached in February 2003 during drought conditions.
“Lake Burley Griffin was lowered 200 millimetres last Friday evening in anticipation of increased water inflows,” he said.
“We will lower the lake by another 300mm. Lowering the lake to this level will assist us in managing risks associated with both the day-to-day operation of the dam and the completion of these engineering works.
“We expect that the lake will remain at this lower level throughout the work.
“There may be occasions when the lake needs to be lowered even further. Lake users will be given advance notice of expected changes in the lake level whenever possible.”
Mr Rake says the dam remains safe and fully functional.
“Undertaking these works will not interfere with the regular operation of the dam. We have been advised by independent engineers that Scrivener Dam remains safe and fully functional,” he said.
“All risks associated with these works and the day-to-day operation of the dam are being appropriately managed.”