From the article posted yesterday.
snip
The open reservoirs hold water that has already been treated and goes directly
into mains for distribution to customers.
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Read more: http://www.myfoxny.com/story/25266957/portland-plans-reservoir-flush-after-teen-cited#ixzz2z9q9uxKQ
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A reservoir open to all sources of potential pollution may be pre-treated but if it goes directly into the feeder pipes as potable then it defies all health codes federal, state, and local. Open source lakes are not potable water. The lake that fed Rapid City SD and Ellsworth AFB was ALWAYS treated and even at that there were several periods in the fall of a year that the smell of the decaying leaves in the lake carried through the treatment and into homes. The water was however treated and never directly fed into the potable water system. I doubt it very much that this is a direct and untreated source for Portland.