Slide # 10 : Water Main Population Risk Groups

Water Main Population Risk Groups

While the mains had some grand-average break probability shown in the power law graph, the very different materials - Thick-Walled Pit-Cast Iron, Thinner Spun-Cast, then Ductile Iron, thinner still - all had different break probabilities; within those, different diameters, and different "corrosion groups" as I called them: with and without copper services. And for Calgary, where there were copper services promoting iron corrosion, I could distinguish higher and lower probabilities within those again, using a soil corrosiveness index. The map on the right shows 100,000 soil tests we did in the 90s that indicate "hot" vs "cold" areas of soil corrosivity.