The case of the man who urinated in an open-air reservoir has drawn attention, and the government is taking action to cover such reservoirs.
But Josh Seater's actions last month that prompted the city to drain the basin isn't the reason.
Portland has five of up to 30 uncovered reservoirs in about a dozen cities around the country.
The fear is that a terrorist could get a toxic chemical into a reservoir and sicken people.
Security was improved after the September 11 attacks and opinions about the extent of the risk that remains are divided.
But the federal government has been cracking down lately on such reservoirs not so much because of potential terrorism but because of health risks - the biggest one being cryptosporidium.
It's a parasite from the feces of infected animals or humans.
Rules in place since 2006 are putting an end to such open-air reservoirs.
Plans are well along in most cities, although it will take years to finish.