Engineer stunned over Creek Bridge ?fiasco


AS a civil engineer, Ernie Armstrong, is skilled at solving complex problems, but even he admits that 'Blind Freddy' would be able to address the risk of flooding that has been factored into the bridge design for the Hogbin Drive extension.

Mr Armstrong was at Thursday night's council meeting when the 'contouring option' ? a five-span 130-metre-long bridge with 200 metres of contour bank which, by the admission of council staff, will raise levels in Coffs Creek during times of flooding by at least 20 millimetres ? was adopted.

He said he was amazed when council's acting director of City Services, Geoff Newton, said he didn't believe extending the bridge by adding up to three spans would reduce the impact of flooding.

Mr Armstrong said he was equally stunned when Mr Newton said that due to consultants being very busy it could take months for them to investigate other options for a bridge to cross Coffs Creek, so he spent Saturday doing some simple modelling.

"Assuming the amount of water flooding down Coffs Creek is constant regardless of what bridge is in place, for an eight-span bridge the channel width spreads the flood water out over 208 metres instead of only 130 metres and, therefore, lowers the flood surface by 0.75 metres," Mr Armstrong concluded.

Councillors were told on Thursday night that adding extra spans would add around $800,000 each to the $5 million cost of the project, but Mr Armstrong argues that in light of his modelling that would be a small price to pay.

"An extra $2.5 million (for three extra spans) is peanuts if we can help reduce the potential suffering of people who would be affected by a 1996-style storm event," he said.

Mr Amstrong said his own investigations over the weekend had found other solutions to the crossing.

"I am reliably told that, after five metres of sludge, the rock under Coffs Creek is particularly hard, and so it would be possible to reduce costs, even after adding the extra spans, by making the pylons smaller," he said.

Mr Armstrong said he feared councillors were being baffled by statistics and rushed into adopting the bridge option that was the quickest to construct.

"Statistics are extremely useful to gauge the order of things. They should not be used as the drunken man uses a lamp post, more for support than illumination," he said.

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