WEAO 07 Conference:INFORMATION DRIVEN ASSET MANAGEMENT – LEVERAGING

This paper by Ross Homeniuk, UMA | AECOM and Hesham Osman, UMA | AECOM was the only interesting paper out of a whole day in the Asset Management track at London’s WEAO conference.

The paper uses NRC CCTV inspection codes (1 to 5 where 5 is collapse) to set up a failure rate model using Markov chains. The result when you recognize that about 3% to 6% of a population of pipes actually get worse enough to move up in the defect assessment codes is that some wastewater pipes have a statistical probability of reaching a useful life of 250 years.

This is a very interesting conclusion because it provides a mathematical method that verifies something that I’ve suspected for a long time. Ever since, that tour of a Roman aqeduct that was built 2000 years ago and would still function today if put into service. Indeed there are examples in the Middle East of infrastruture that is hundreds and thousands of years old that is still in service.

The difficulty is that the analysis of the markov chain only provides a decay curve for pipes that progress to a collapse failure. What about the class of pipe that decays but does not progress to a collapse failure? (Most of the sample data is based on the City of Winnepeg infrastructure). This analysis does not include those pipes that are considered to have failed because they leak like a sieve and cause downstream flooding problems. This a class of pipe failure that is related to an I&I problem. It may not result in a complete pipe replacement but in an in situ rehabilitation technology; however, the result of incurring a capital expense that is a betterman, (extension of service life) is the result.

So I suspect that the analysis may have be a bit too uniform in its treatment of pipe failure types. There may be other ways that a pipe can fail that do not fit in this analysis.  A really interesting bit of work though and very well presented. Kudos to the authors.

Valley Center Municipal Water District agrees to buy water

The plant would have a capacity to produce of 56,000 acre-feet a year. An acre-foot is the amount of water it takes to cover 1 acre a foot deep, or about 326,000 gallons, which is enough to supply two average households for a year.

Let’s convert these numbers to SI and make a comparison with our own typical consumption figures. An acre-foot of water is equivalent to 1,233,481.8 liters which is said to supply two average households for a year. They are reporting then that the average household consumes about 615,000 litres per year. Using a per capita consumption figure of 300 litres per capita per day and 2.3 people per house, we arrive at 252,000 litres for an average household excluding system losses, etc. That’s 2.5 times less water for an average household based on 2.3 people per household. From an AWWA paper that I can recall from the 80′s, I believe that water consumption grows with income and property value so it is possible that this statistic is being reported for a uppper income area.
This is the other quote that I find interesting.

“In reality, desalinated water will never reach Valley Center,” Arant said. Instead, the district will swap an equal amount of imported water for desalinated seawater with an agency willing to make the trade, and then that district will get the desalinated water.

He said Poseidon will have to line up that partner.

The agency is agreeing to buy water in order to make a swap for with another agency. The water procurement game in the US continues to impress and faces even greater challenges as the SW US growth puts further pressure on water supplies.

Full Story here.

Debt-ridden M.W.R.A. to hike up water rates over next five years

HOLBROOK (AP) — A new survey says thousands of residents south of Boston will be faced with water and sewer rate increases of more than 40 percent over the next five years.

story is here.