Heavy Rains Cause Combined Sewer Overflow Into Willamette River, Officials Say

PORTLAND, OR — Bureau of Environmental Services officials on Sunday said heavy rain in Portland over the weekend caused an early morning combined sewer overflow into the Willamette River.

Around 1:15 a.m. Oct. 22, multiple outfalls spilled roughly 80 percent stormwater and 20 percent sanitary sewage into the river, officials said, noting the volume spilled is currently unknown.

Community members are encouraged to avoid contact with the Willamette River indefinitely, as overflows appear to have continued late into Sunday. Typically, overflow events result in a 48-hour advisement to avoid contact with the contaminated water.

Forecasters with the National Weather Service — Portland Office said the metro region took on nearly 3 inches of rainfall between Friday and Sunday, putting extra stress on the city's sewer system.

Due to the "Big Pipe project" in 2011, officials said combined sewer overflows into the Willamette River have decreased 94 percent from an average of 50 times per year prior. Officials said sewer overflows will now likely occur roughly four times each winter and once every three summers.

According to officials, the $1.4 billion Big Pipe project consisted of several improvements to how the city's stormwater is drained and saw the construction of large pipes on the river's east and west banks, as well as along the Columbia Slough — which also saw a 99 percent reduction in sewer overflow events after the project's completion.

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