PORTLAND, Ore. >> The mix of 38 million gallons of treated water and one teen’s urine has proven unacceptable to Portland officials who plan to flush away the whole lot — the second time in less than three years the city has gone to such lengths to keep its water pure.

In June 2011, the city drained a 7.5 million-gallon reservoir at Mount Tabor in southeast Portland. This time, water from a different reservoir at the same location will be discarded after a 19-year-old was videotaped in the act.

“The basic commandment of the Water Bureau is to provide clean, cold and constant water to its customers,” bureau administrator David Shaff said Wednesday. “And the premise behind that is we don’t have pee in it.”

The open reservoirs hold water that has already been treated and goes directly into mains for distribution to customers.

The urine poses little risk — animals routinely deposit waste without creating a public health crisis — but Shaff said he doesn’t want to serve water that was deliberately tainted.

“There is at least a perceived difference from my perspective,” Shaff said. “I could be wrong on that, but the reality is our customers don’t anticipate drinking water that’s been contaminated by some yahoo who decided to pee into a reservoir.”

Water-quality test samples have been taken from the reservoir, with the results due Thursday. The water will be drained into the sewage system, eventually reaching a treatment plant before it’s dumped into the Columbia River.

In the meantime, Shaff said the city has plenty of water to meet demand.

“It’s easy to replace those 38 million gallons of water,” Shaff said. “We’re not in the arid Southwest. We’re not in drought-stricken parts of Texas or Oklahoma.”

The incident occurred shortly after 1 a.m., when Water Bureau security personnel noticed three men on camera at Mount Tabor Reservoir No. 5. One was seen on video urinating through an iron fence, officials said. Minutes later, two other young men attempted to scale the fence.

The three men, whose names have not been released, were cited for trespassing and excluded from Mount Tabor Park. A 19-year-old was cited for public urination.

The Multnomah County District Attorney’s Office will decide whether to pursue criminal charges.

The kidney-shaped reservoir built in 1911 is drained for cleaning each spring and fall. The spring draining was done about three weeks ago, the Water Bureau said.

The reservoir is one of five the city is in the process of replacing with underground storage to comply with federal regulations.

Floy Jones, co-founder of the group Friends of the Reservoirs, criticized the decision to drain the reservoir, saying there’s no evidence any urine reached the water and it wouldn’t harm anyone if it did.

“It’s extremely wasteful,” she said.

The man who urinated into Portland’s water supply in June 2011 eventually pleaded guilty to misuse of a reservoir and was sentenced to community service.