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Dammed water a drop in a bucket in flood
To the Editor,
Re: Colliery dam risk lowered, May 29.
In 2012 city council was told that the Colliery dams were in such poor condition that there was a 40 per cent chance in 50 years that they would fail in a manner that would cause swaths of destruction in lower Harewood. Thanks to the most intensive analysis that may ever have occurred on a dam in B.C. we know that this is not the case. At most, an earthquake could cause cracking and they could leak. We are now left with dealing with a hypothetical flood event. Despite studies showing that the spillways are undersized, our dams have successfully managed storms over the last century. For much of the year we have about 2.5 centimetres of water or less in the spillway and very rarely have more than 0.3 metres.
An enormous flood event that could impact the dams would occur over many hours or days. Should an event like this occur, there would be large-scale flooding in most of Nanaimo with a great deal of damage. This is unrelated to our dams. Our two lakes are very small and even if they were to lose their water, it would not be instantaneous and would have little overall impact.
As for the signage, our society has asked repeatedly for them to be removed. We consider them to be a blight in our community with no actual benefit.
Colliery Dam Park Preservation Society
To the Editor,
Re: Extreme weather will stress our dams, Letters, June 12.
In the two extreme rain and snow events the letter writer mentions, none of this fear-mongering erosion has happened. No cracks found, either.
But speaking of cracks in concrete, they are very dangerous. I’m speaking as a man that has done a lot of commercial concrete form work, pouring concrete and seeing the results. A cracked wall or floor will not pass, usually caused by stripping the forms too soon on green concrete. Nanaimo now has this problem at the new reservoir at Colliery Dam Park.
Yes, leave the flood signage in place, because if we get the big one I’ll be betting the new reservoir will fail long before the old dams.