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Number of Corrective Flushings of Sewer Mains vs. Count of Sewer Mains

At first, I assumed I'd found some amazing new law about the corrosion of iron. Something about steady corrosion rates but frequency of appearance of pits had some distribution that showed up as a power law for actual holes.

Then Calgary Waterworks merged with Sewer, giving me Sanitary and Storm systems in my database. Soon after, I was graphing the rough equivalent to main breaks for sewer: the number of times they needed a corrective flushing. Understand this isn't about corrosion and holes, just how often gravel and plastic bags and other debris plug one up. It's related more to usage, house density, and slope of the main. None of that mattered except to pick the exponential constant and the coefficient: it was another power law.

© Roy Brander, P.Eng 2016