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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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Heavy rain causes sewer overflow to the Willamette River

CSO Advisory

January 17, 2015

Heavy rain on Saturday, January 17, 2015 caused Portland’s combined sewer system to overflow to the Willamette River. The public should avoid contact with the river from the Sellwood Bridge downstream to the Willamette’s confluence with the Columbia River near Kelley Point Park.

As a precaution, the public should avoid contact with river water downstream of the Morrison Bridge until 48 hours after combined sewers stop overflowing. More details are posted at 

It is especially important to avoid recreational activities, such as jet skiing or swimming, during which water could be swallowed. CSOs are contaminated with bacteria from untreated sewage. Environmental Services recommends these precautions to protect public health.

Portland’s combined sewer system carries sewage and stormwater runoff in the same pipes. During very heavy rainstorms, the increased stormwater runoff can cause combined sewers to overflow into the Willamette River.

In December 2011, Portland completed a 20-year program to improve the sewer system and reduce Willamette River CSO events from an average of 50 per year to no more than four per winter and one every third summer.

For more information contact Linc Mann, 503-823-5328.

The Bureau of Environmental Services provides city residents with programs to protect water quality and public health, including wastewater collection and treatment, sewer construction and maintenance, stormwater management, and stream and watershed restoration.