Wall designer warns of a flaw
THE ORIGINAL designer of the Grafton levee said Clarence Valley Council ignored a letter warning of a flaw around Fry St.
Trevor Jones, who still lives in Grafton, wrote to the council about five years ago after he and the surveyor on the levee project, Ori Pastega, noticed the levee was lower in the area of Fry St than the rest of Grafton.
Mr Jones said the level at Fry St dropped about 8cm and was too low.
He said the levee was designed to breach at the same time at all points around Grafton to avoid flash flooding.
"If it all breaches at the same time the water will come through in a trickle," Mr Jones said.
"However, if it breaches in just one spot it will rush through the hole quickly."
Mr Jones also said the levee in South Grafton was at 8.6 metres whereas the levee in Grafton proper stood at 8.2 metres.
"The South Grafton levee was built under a more sensible policy aimed at giving more free-board," Mr Jones said.
"We were very fortunate this time. It was a planned miracle really."
Clarence Valley Council operations manager Tim Jenkins said he was unsure if Fry St was a low point. "Do I know categorically if there is a low point at Fry St? No," Mr Jenkins said.
Deputy general manager of the council Rob Donges said the local authority received Mr Jones's letter in 2009.
He said it was ignored because if Mr Jones's calculations were correct the levee should have topped at Fry St during previous floods. He said the water did not overflow at Fry St despite frantic sandbagging efforts and water being pumped out on Tuesday during the floods.