PORTLAND, Ore. (KOIN) — Officials from the Portland Bureau of Environmental Services are advising the public to avoid contact with the Willamette River downstream of the Ross Island Bridge until 5:30 p.m. Sunday.
The atmospheric river that flooded portions of central and northwest Oregon caused a combined sewer overflow to the Willamette River on Friday morning, leading city officials to issue the advisory.
PBES said the city’s Big Pipe system, which helps keep sewage out of the river, reached 100% capacity around 6:30 a.m. Friday.
A subsequent overflow into the river then began and lasted about 11 hours.
The City has advised everyone to avoid contact with the river during an overflow and for at least 48 hours afterward due to the threat of increased bacteria in the water.
“The pattern is different,” said Diane Dulken, a spokesperson for PBES. “We’re seeing an atmospheric river roaring through Portland, it’s causing widespread impact, and this overflow which started at about 6:30 this morning is continuing.”
Dulken told KOIN 6 News improvements to Portland’s sewer system have dramatically decreased the number of yearly sewage overflows.
Since the 2011 installment of the Big Pipe project, PBES says the amount of yearly overflows has dropped from approximately 50 times a year to an average of four annually.
“Thanks to our new system these overflows are rare,” Dulken stated. “But this is just the kind of weather; the intense rainstorms, all at once, for multiple hours that will cause the system to reach capacity. And that’s what’s happening now.”
According to PBES, these types of overflows typically occur during periods of heavy rain or snow. This is the fourth combined sewage overflow this year.
“Overflows are an estimated 80% stormwater and 20% sewage,” Dulken explained. “That combination of diluted sewage runs into a river which has a high volume to begin with, and additional volume due to rain. So, the sewage gets diluted, but it’s still there. We want to let people know when that happens, so they can be safe.”
Dulken told KOIN 6 News officials plan to update the public when the overflow stops.
Keep up with the status of the overflow and the Big Pipe system via the Big Pipe Tracker.
An atmospheric river inundated the Pacific Northwest with torrential downpours, resulting in river flooding warnings on the Oregon Coast, localized flood watches in the Willamette Valley and more. Click here for a full list of active weather alerts.