Scientific Method / Science & Exploration

Draining reservoir after urination incident shows tenuous grasp of science

Portland throws out 38 million gallons of water after someone peed in it.

Dallas Swonger, right, caught in the act by a security tape.

The city of Portland, OR will empty a 38-million gallon reservoir after a teenager allegedly urinated in it, according to the Associated Press. It's the second time in three years that Portland is flushing its Mount Tabor reservoir after a urine-related incident.

The reservoir is open-air and sits exposed to all of nature, leading many parties to question how necessary a draining would be, or how polluted 38 million gallons of water can really be by a single man's urine.

David Shaff, Portland's water bureau administrator, reserves a special disgust specifically for human urine. In 2011, when Shaff drained the reservoir following a urination, he reasoned to the Portland Mercury, "Do you want to be drinking someone's pee?… There's probably no regulation that says I have to be doing it but, again, who wants to be drinking pee?" This time around, Shaff wrote in a statement, "Our customers have an expectation that their water is not deliberately contaminated."

A half-liter of urine dumped in a 143 million-liter reservoir would get a urea concentration of about 3 parts per billion, according to Slate. (We calculated it would be a 50 nanoMolar solution.) Meanwhile, the EPA allows concentrations of arsenic in drinking water up to 10 ppb. Salt water has a salt concentration of around 35,000,000 parts per billion, or 600 milliMolar.

In an interview with Vocativ, the teenager in question, Dallas Swonger, denied urinating in the reservoir at all, stating he actually hit a wall instead. "I leaned up against the wall and pissed on it," Swonger said. Swonger also contested the cleanliness of the reservoir prior to his actions: "I’ve seen dead birds in there. During the summer time I’ve see hella dead animals in there," Swonger told Vocativ. In 2011, Shaff told the Mercury that the reservoir is not shut down for nature's transgressions. "If we did that, we'd be shutting it off all the time. We fish out animals or things that have blown in all the time," Shaff said.

The reservoir will reportedly cost $36,000 to clean and had just had one of its twice-yearly cleanings three weeks ago.

Update: The cost cited refers to Portland's earlier incident, when Shaff reported the incident would cost the city $36,000. The price of draining and restoring the reservoir following the 2014 incident may differ, since the quantity of water is vastly larger.

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