Heavy rains cause sewer overflow in North Portland
Heavy rains caused a short-lived combined sewage overflow Sunday from a maintenance hole at North Burlington Avenue and Edison Street into the Willamette River in Portland.
According to the Bureau of Environmental Services, the overflow began at approximately 1:30 a.m Sept. 19 and stopped at 1:40 a.m. The volume of the overflow is unknown.
The bureau said that as a precaution, people should avoid contact with the Willamette River in that area for at least 48 hours after the discharge has ended because of the possibility of increased bacteria in the water.Â
A combined sewer overflow (CSO) is about 80% stormwater and 20% sewage. They are rare and can occur during periods of heavy rain or snowfall.
Since completing the Big Pipe project in 2011 — a 20-year $1.4 billion program to reduce overflows — the number of CSOs have dropped by 94% into the Willamette River and 99% to the Columbia Slough, the bureau said.
The Big Pipe project included a series of improvements, from disconnecting downspouts on homes to allow rainwater to be absorbed naturally in the ground to the construction of big pipes on both sides of the river and along the slough to store and convey large quantities of flows to the Columbia Boulevard Wastewater Treatment Plant.
Before the project, CSOs occurred in the Willamette River from multiple outfalls an average of 50 times a year, with some instances lasting days. Today, overflows occur an average of four times per winter season, and once every three summers, the bureau said.
This is the first CSO since January 2021.
Find out more information about CSO events, what they are and why they occur atÂ www.portland.gov/bes/about-csos.
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