August 2006 Newletter

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This newsletter will be discussing raw water and chlorine. If those topics interest you, keep reading. If not, this is a good place to stop.

“Raw water” describes what comes off the mountain. “Finished water” has passed though all the treatment steps and is ready to drink. Recently, the Board of Directors has been working to assure that our raw water supply is adequate.

Historically, the Association has been able to purchase water when the need and the opportunity arose. The membership fee which is charged for every new tap is used partly to pay for the water that tap will require. The membership fee has been increased periodically to cover inflation in water cost (along with the inflated cost of everything else). That system has worked well in the past, particularly since the growth of the system has been reasonably uniform, without huge boom or bust periods.

However, that picture is changing. The cost of water is not as predictable as it has been, and the ability to obtain it is not assured. Therefore, the Board has adopted a policy which requires any applicant for four or more new taps to provide the Association with one acre foot of raw water for each tap. An acre foot is about 325,000 gallons. The Association members do not use one acre foot per tap per year. We use less than ½ acre foot. However, most raw water is decreed for irrigation. If used for domestic purpose, only about half the water is available. The rest must be allowed to remain in the stream, to mimic the runoff that is assumed to occur from irrigation.

The Board recognizes that it may eventually become necessary to apply this policy to all taps. For the time being, it only affects major subdivisions, which are the most likely to place sudden demands on the water supply and delivery capacity.

Now, about chlorine. Chlorine is the disinfectant of choice by USCDWUA because it is easy to apply, reasonably economical, and provides a persistent residual in the distribution system. It is this residual that is most often the topic of controversy. To some consumers, any residual is too much. To the Health Department, a residual is an absolute requirement.

At the point of greatest chlorine concentration, which on our system is at the beginning, the law requires a concentration of less than four parts per million, and more than 0.2 parts per million. Four parts per million is much more than we need, and 0.2 parts is not enough. Typically, we have 1.5 parts per million. This dose ensures a residual which persists throughout the system with a strength that can combat potential contamination. What contamination? Well, dirt for example, which can enter when a backhoe rips out a main line. Or an illegal cross connection with another water source. There are many possibilities.

It may seem that we could learn exactly how much to dose at the treatment plant in order to achieve a barely detectable residual at the end of the system, thereby remaining legal. This ideal is not easy to obtain. The persistence of chlorine in the distribution system is subject to a variety of factors: reaction with the pipe walls, dissipation in tanks, water temperature, just to name a few. In reality, we choose to err on the side of safety, and shoot for more than the bare minimum.

We prefer not to engage in debates over health problems claimed to be caused by drinking chlorinated water. As operators, our responsibility is to follow the regulations and ensure public safety. We recognize that some people do not like the taste, and that some are unusually sensitive, and that some are actually allergic. While we sympathize, we cannot tailor the chlorine dose to accommodate every preference. But you can. A simple and inexpensive activated charcoal filter will do a great job of removing chlorine from your tap water. We recommend it if chlorine is intolerable for you.


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