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The City of Portland, Oregon

Environmental Services

working for clean rivers

Phone: 503-823-7740

Fax: 503-823-6995

1120 SW 5th Ave, Suite 613, Portland, OR 97204

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CSO Advisory: City recommends caution for Willamette River use

City recommends caution for Willamette River use

The recent rainstorm has causedPortland’s combined sewer system to overflow to theWillametteRiver.

The combined sewer overflow (CSO) event began at about 2:45pm today following nearly 3-inches of rain over the last three days, and specifically due to more than 2-inches of rain in the last 24-hours.  CSO discharges will continue intermittently over the next few days due to the series of large storm cells forecasted for this week.  The public should avoid contact with river water for 48 hours after the end of the CSO event.

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.

People who fish during or soon after a CSO event should wash their hands following contact with river water. Those who choose to eat fish caught in theWillametteRiverduring or soon after a CSO event should cook the fish thoroughly to kill bacteria.

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 theWillametteRiver.

In December 2011,Portlandcompleted a 20-year program to improve the sewer system and reduce Willamette River CSO volume by 94%.  The program reduces CSO events from an average of 50 per year to an average of four per winter and one every third summer.


For more information contact Debbie Caselton, 503-823-2831