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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 Overflow (CSO) Advisory

June 1, 2011

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

City recommends caution for river use

Due to the recent rainstorm, Portland's combined sewers have overflowed to the Willamette River.

The public should avoid the Willamette River for 48 hours after the rain has stopped. It is especially important to avoid recreational activities–such as water skiing, jet skiing or swimming–during which water could be swallowed. Combined sewer overflows (CSOs) are contaminated with bacteria from untreated sewage. Environmental Services recommends these precautions to protect public health.

People who fish should wash their hands following contact with the water. Those who choose to eat fish caught in the Willamette River during a CSO event should cook the fish thoroughly to kill bacteria.

In many areas of Portland, sewage mixes with stormwater runoff in a combined sewer system. When the combined sewers receive too much runoff, they overflow into the Willamette River.

Portland is in the final year of a 20-year program to improve the city's sewer system. Until the program is complete in December 2011, overflows of untreated sewage and stormwater will occur during some rainstorms.

After all CSO projects are complete in December 2011, combined sewers will overflow an average of four times each winter and once every three summers instead of an average of 50 times per year.