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Environmental Services

working for clean rivers

Phone: 503-823-7740

Fax: 503-823-6995

1120 SW 5th Avenue, Room 1000, Portland, OR 97204

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Combined Sewer Overflows (CSOs)

Portland's River Alert Program 

There is currently no combined sewer overflow (CSO) advisory in effect.

Environmental Services issues a CSO advisory each time Portland’s combined sewer system overflows. 

In December 2011, Portland completed a 20-year program to improve the sewer system and reduce annual Willamette River CSO volume by 94%. The West Side and East Side Big Pipes collect and convey most combined sewage to the city’s wastewater treatment plant. The program reduced CSO events from an average of 50 per year to no more than four per winter and one every third summer.

For more information about the River Alert program, call 503-823-2479.