PORTLAND, Ore. -- Call it the big flush.

Because a 21-year-old man was caught on a security camera urinating into a city reservoir, Oregon's biggest city is sending 8 million gallons of treated drinking water down the drain.

Portland officials defended the decision Monday, saying they didn't want to send city residents water laced, however infinitesimally, with urine.

Public health officials say, however, that urine is sterile in healthy people and that the urine in the reservoir was so diluted -- perhaps a half pint in millions of gallons -- that it posed little risk.

Some people in the city, in the suburbs and around the world called the flush an overreaction, especially since animals such as ducks contribute waste routinely and, sometimes, die in the water.

"More than 1 billion people worldwide do not have reliable access to clean drinking water, and here we are tossing away nearly 8 million gallons of water just to appease the ignorant residents who believe their tap water will otherwise turn yellow," read one comment posted on The Oregonian's Website.

Water from the city's five open air reservoirs, all in parks, goes directly to customers. The reservoirs are due to be replaced by underground storage within a decade, a result of federal requirements.

The reservoirs distribute water that flows from glaciers on Mount Hood. It is treated before it goes to the reservoirs for distribution, and then goes directly to consumers.

The reservoirs are drained twice a year for cleaning, and workers have found animal carcasses, paint cans, construction material, fireworks debris and even the plastic bags people use to scoop up after their dogs, said David Shaff, administrator of the city water bureau.

Even so, Shaff said, the yuck factor was the primary reason for the decision to drain the 8 million gallons, at a cost of less than $8,000 to treat it as sewage.

"Nobody wants to drink pee, and I don't want to deal with the 100 people who would be unhappy that I'm serving them pee in their water," he said. Shaff said the security cameras also showed something that's still unidentified was thrown in the water, heightening concern about potential risks.

City Commissioner Randy Leonard, who is in charge of the water bureau, defended the decision, citing a potential public health risk. He said he worried about the possibility of chlamydia or AIDS from blood in urine.

"I'm for taking the most conservative approach," he said.

Dr. Gary Oxman, the county health officer, said the risk was so close to nil that it falls in the "never say never" range. Even with the uncertainty over an object thrown in the water, "that's still a very small risk," he said.

The young man, Josh Seater, told KATU-TV he'd been drinking, was with friends and thought that the reservoir was a sewage treatment plant. He said he felt guilty instantly, and then security guards arrived.

"I knew I did wrong when I did it," he told the station.

In addition to the sewage charge, Shaff said, the flushed water is worth $28,000.

The Mount Hood watershed that supplies the city is brimming this spring, with 8 million gallons flowing through it about every half hour.

"If I lived in Texas, I might have had a different response," he said.