You've seen the sign before: "Warning! Sewage Spill: Avoid water contact." While the Willamette is no flammable Cuyahoga, the six-mile stretch from the Steel Bridge to Sauvie Island is a federal Superfund site in the preliminary stages of a massive effort to reduce the effects of years of dumping of heavy metals, pesticides, herbicides, oils and coolants by ships and manufacturers along the river. The sewers in Southeast Portland overflow into the river almost every time it rains, and anyone who's lived here more than a few days knows you don't swim in the water. Why? Because it's toxic. Right?

Jay Boss Rubin, co-founder of the now-defunct Portland Challenge event—in which hundreds of Portlanders would ford the river without using money, motors or bridges—swam the span of the Willamette every summer since 2003. "It's disgusting," he says. "That's the idea, actually. It's disgusting but it's real—that's what makes swimming in the Willamette River a transformational experience." Fortunately, the transformations don't involve mutations. "I've never suffered any negative physical consequences as a result of swimming in the Willamette River," he says, "but I know people who have…so you have to be a little superstitious about swimming in the Willamette. Maybe someday it'll be simpler. Maybe someday it'll just be taking a dip."

Joe, a Portland Challenger who asked us not to use his last name, said his second attempt to swim the river didn't end well: "It's impossible not to get some of the water in your mouth. I had the shits for a few days after. It was a low-grade, all-around discomfort. I never went back in. I didn't feel like repeating that."

Doug Drake, Lower Willamette Basin coordinator at the Oregon Department of Environmental Quality, strongly suggests washing your hands with soap or taking a full shower soon after your river dip, but says that "swimming in the Willamette or swallowing a few mouthfuls of water isn't going to kill you." The biggest hazard in the river is the level of general bacteria, he adds, which is measured by E. coli, otherwise known as the icky-nasty-yuck bugs in dog poop, human poop and leaky septic systems. "It's probably the greatest human health risk besides eating some of the resident fish," Drake says (the fish contain high concentrations of mercury).

Apparently it's also the easiest pathogen to detect. Normally, there's a "99.99 percent chance that there's no problem," and when there is, especially after a huge storm when the stormwater and sewer lines are overloaded, the city will issue a press release to warn us that toxins have been released into the river. At that point, we'd stick to a swimming pool for summer fun (see "Splish Splash" to find out more).