THE WILLAMETTE RIVER will not kill you.

If you are so inclined to take a dip in its waters, your body will not become riddled with Hepatitis A through Z, your immune system will not succumb to some sort of aquatic leprosy, a toxic manatee will not drag you deep into the river's murky depths, and if you toss your lit cigarette into the river—which you really shouldn't do—the water will not ignite in a ball of flames that stretches to the heavens.

You will be fine.

But please—don't just take my word for it. According to the Oregon Department of Environmental Quality, "The Willamette River in Portland is safe for swimming and other recreational uses at most times of the year." Need more proof? Take it away, Rick Bastasch, program coordinator for the City of Portland's Office of Healthy Working Rivers: "The Willamette, most time of the year, is clean for swimming, clean for water contact, safe for water contact."

It breaks down to an issue of rainfall. Simply put: If it rains, stay out. If it is dry for more than 24 hours straight, feel free to go in. That said, it's unlikely you'll ever do such a thing. Despite claims from educated sources, the body of water that neatly slices this city in half still haunts us. Shortly after being told how to pronounce the Willamette, we're told to never—never—dip a toe in its noxious waters. There is a rational line of thought behind this. The city's waste overflow finds its way into the river after every big rain, which, as we all know, is all too often here. And it's been this way for far too long. According to the nonprofit Willamette Riverkeeper, less than 50 years removed from Oregon's induction into the Union there were complaints from Portland's old-timey residents that the river's waters were unfit.

"People's habits were very different in 1898 than today," says Bastasch. "There are bad things in the sediment, and if they get stirred up then they can find themselves in the food chain, and that's why there are fish consumption advisories. If we, as humans, eat a lot of those fish, that's where authorities get concerned. When you jump in the Willamette, and swim in the water, and splash in the water, it's safe. If you're talking about its long-term ecological health, we have some work to do there."

Part of that work is the Combined Sewer Overflow Control Program, better known by its sexier title, the Big Pipe. The Westside of the city already has their Big Pipe in place, while the Eastside gets theirs later this year, most likely by fall (and no later than December 1). "You can pick up that the west bank is cleaner," explains Bastasch. "The plume of bad stuff during a rain or overflow event is confined to the Eastside, and soon that's going to be dialed down."

Linc Mann, from the Portland Bureau of Environmental Services, knows this better than most, and he explains that the Big Pipe program is part of a two-decade-long plan to keep overflow sewage out of the water. "We still get combined sewage overflows, but they are nowhere near as big as when we started this 20 years ago."

In a noble effort to encourage us Portlanders to shed our ingrained fear of the Willamette and actually celebrate the iconic river that defines the city, the Willamette Riverkeeper and the City of Portland have teamed to sponsor the first annual Big Float on Sunday, July 31. Put your fears to rest and join this floating parade of inner tubes and rafts (or whatever floatation device you prefer), which will travel from the west side of the Marquam Bridge to a docking spot across the river. (Don't worry if your aquatic skills are less Michael Phelps and more flailing wildly in the water—there will be kayak "chaperones" to help you cross.)

Once on dry land, you can either return to the water for additional swimming or partake in the Big Float's epic (Mercury-sponsored) afterparty, loaded to the brim with some of the finest musicians in town. There's the haunted beach blanket shuffle of Orca Team, the quirky folk stylings of Keep Your Fork, There's Pie, the vintage vocal-heavy pop of AgesandAges, and finally, a closing set from the wondrous art-rock of Ramona Falls. In addition, there will be all sorts of food carts and other events to help you celebrate your glorious crossing of the river.

Even with a litany of endorsements from distinguished experts and the promise of music and revelry awaiting you on the other side, there will always be trepidation about the Willamette River. It's been instilled in all Portlanders, both natives and new residents alike, but the days of fearing the river are a thing of the past. As Mann explains, "On a nice dry day, the river is in much better shape than it has been in years past. I don't think there is a health issue with this at all."

Come on in, the water is fine.