Referance materialFrom reading the pdf in Ekka's post, it didn't take long for me to realize that the tree again are gettin' the blame for the shortcomings of man. The tree roots DO effect sewer blockages, however in our part of the world sewer pipes have to be buried BELOW the frost line, and that would be at least 10' deep.
I don't pretend to know how deep Melborne burys their sewer line, but I would bet that the sewer lines that are blocked are old CLAY lines, which are perhaps fractured OR have leaky seals at joints. A couple years ago I attended a conferance where Drs. Kim Coder and Ed Gilman were speaking to the issues of TREES AND INFRASTRUCTURE. The one point that Dr. Coder made was that as a rule a tree will NOT send a root into soil that doesn't have at least 10% oxygen in it. This being said,if a sewer line fails, we have two things that a tree needs to survive, oxygen and moisture.
We have removed LARGE poplars that had declined to near total death, from nitrate poisioning from a septic tank. The very first cut to live tissue immediatley woke up my sense of smell. I believe the trees that are the worst vialator of sewer lines are species that are NOT water thrifty (Drought tolerant). In Canada the BIG three would be Poplar, WIllow and Birch.
I am NOT a tree hugger, but I am getting a little ticked off at City managers blaming the trees when in fact it is peoples fault for failing to think through all the possible senarios to the conflict between man and nature. I am going to attach a link to Dr. Gilmans site, where he is conducting an experiment on sidewalks, they are in the Power Point section. Dr. Gilman has my utmost respect for making his work available to the general public. The link is
Pruning - Landscape plants - Edward F. Gilman - UF/IFAS