Phone: 503-823-7740
Fax: 503-823-6995
1120 SW 5th Ave, Suite 613, Portland, OR 97204
Combined Sewer Overflow (CSO) Information
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Portland finished construction in 2011 to control combined sewer overflows (CSOs)
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CSO construction took 20 years and the city finished it on time and on budget
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CSO construction reduced overflows from about 50 a year to only four or five
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Today only the heaviest rain storms can cause an overflow
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News advisories and signs warn the public of CSO events
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Green streets and rain gardens keep stormwater out of the big pipe system
Why Portland has Combined Sewers
When the City of Portland began constructing sewers in the late 19th century, sewer pipes carried stormwater, sewage and industrial waste - all combined in the same pipes - directly to the Willamette River and Columbia Slough without treatment.
Watch the CSO program video for more
Enjoy the River
Thanks to the CSO control program, the Willamette River and Columbia Slough are cleaner than they've been in generations. Willamette River water today is safer for swimming.
Check the Willamette recreation index for E. coli and temperature information
Green Infrastructure
Portland uses rain gardens, green street planters, and other green infrastructure to keep stormwater out of combined sewers and ensure that the Big Pipes continue controlling overflows now and for generations to come.
Learn about green street planters, ecoroofs and other green infrastructure