Sewage overflows into Willamette River as atmospheric river hammers Pacific Northwest

PORTLAND, Ore. (KOIN) – After an atmospheric river brought heavy rain to the Pacific Northwest, a stream of stormwater and sewage overflowed into the Willamette River after Portland's Big Pipe system reached capacity, the Portland Bureau of Environmental Services announced Wednesday.

Officials said the Big Pipe system reached capacity around 7 a.m., leading to stormwater and sewage overflowing from multiple outfalls. The overflow is impacting the downstream stretch of Sellwood Park and is ongoing, according to a press release sent shortly after 8 a.m. Wednesday.

The public is advised to avoid contact with the river for 48 hours after an overflow because of increased bacteria. The city explained the Willamette River’s water quality is safe for recreations during all other times.

Overflows contain about 80% stormwater and about 20% sewage, officials said, noting overflows are rare but can occur during heavy rain or snowfall.

Portlanders can track the overflow through the online Big Pipe Tracker.

After the Big Pipe project was completed in 2011, the system has reduced overflows by 94% in the Willamette River and 99% in the Columbia Slough, the city says. Before the Big Pipe was in place, officials say incidents occurred in the Willamette River 50 times a year on average.

Now, overflows occur four times per winter season and once every three summers on average, according to BES -- noting Wednesday’s overflow is the fourth overflow of 2023.