Less than a decade ago, swimming in the Willamette River would have been a game of bacterial Russian roulette.

That's because the city's sewer system, which shared pipes with stormwater drainage, was prone to overflowing with as little as a 10th of an inch of rainfall. In the early '90s, according to the Bureau of Environmental Services' website, "an average of 6 billion gallons of combined stormwater and sewage overflowed to the Willamette River and Columbia Slough every year."

But last December, when Portland experienced an "atmospheric river" that dumped 3.1 inches of rain on Mount Tabor and 1.5 inches in the West Hills, there were zero shits to be found in the Willamette.

What changed? The Big Pipe.

Thanks to a $1.4 billion investment from the city in 2011, two massive tunnels on either side of the river now direct your excretions to a treatment plant on North Columbia Boulevard.

"The Big Pipe is working and the Willamette is the big winner," City Commissioner Nick Fish, manager of the Bureau of Environmental Services, told WW in December. "Bring it on, Mother Nature!"

The Big Pipe project now successfully diverts 94 percent of sewage from ending up in the river. Frequent E. coli tests by the city show that bacteria from the small percentage of feces that does escape the sewer does not make the river unsafe to recreate in.

Just remember: "Even though Willamette River bacteria levels are low," the bureau cautions, "it's never safe to swallow water from urban rivers and streams."