Portland has open air reservoirs in Mt. Tabor and Washington Park. They're both fenced off, but I do know that dead animals have been found in the Washington Park reservoirs before. what was surprising to me is that this is the first time I realized that the water in these reservoirs has already been processed. I always assumed that they held pre-processed water.

Oh well, at least it isn't as bad as when sewage overflows get released into the Willamette River every few years.