science environment

60,000 Gallons Of Wastewater Flow Into Willamette River After 'Unusual' Rainfall

By Rebecca Ellis (OPB)
Aug. 11, 2019 9 p.m.

Tens of thousands of gallons of sewage and stormwater have flooded into the Willamette River after an abnormally heavy rainfall Saturday evening caused Portland's sewer system to overflow.

Beginning in the late afternoon, a slow-moving storm dumped nearly 0.80 inches of rain on Northeast Portland. The deluge of water overwhelmed the sewer system, leading to an estimated 60,000 gallons to overflow into river near Portland’s Linnton neighborhood.


With the raw sewage runoff comes dangerous bacteria, capable of causing illnesses ranging from stomach cramps to cholera. Officials are warning the public to stay away from the water downstream of Linnton until Monday evening.


Before the city invested more than a billion dollars in revamping its sewer system, overflows occurred an average of 50 times each year. Since the improvement project wrapped up in 2011, the city reports the number of overflows into the river has dropped by 94%.

Overflows are now expected four times each winter, and once every three summers, according to the city’s Bureau of Environmental Services.

But Saturday was not a typical summer day: Portland saw more rainfall in the early evening of Aug. 10 than it usually sees during the entire month. Less than 0.70 inches of rain typically fall on Portland each August, according to David Bishop, a meteorologist with the Weather Service’s Portland office.

The Portland NWS tweeted that Saturday had become the rainiest Aug. 10 on record, as well as the second wettest day of 2019, so far. But, Bishop cautions, that doesn't mean everyone in the surrounding area was hit with an unprecedented torrent of raindrops. The measurement was taken at Portland International Airport.

“The Vancouver Airport is just across the Columbia, really not that far away,” he says. “They got a total of 0.14 inches yesterday.”

No more heavy rain is forecast for the upcoming week.