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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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UPDATED CSO Advisory: Combination of stormwater and sewage overflows from SW Carolina Street outfall to the Willamette River

UPDATE (May 15) - The total amount of stormwater and sewage overflow on Saturday is estimated to be 5,100 gallons. The source of the suspected debris blockage remains under investigation. 

(May 13, 2017) – Environmental Services is reporting a combined sewage overflow (CSO) from the SW Carolina Street outfall  north of Willamette Park to the Willamette River. The overflow began about 5 p.m. and lasted about ten minutes. Additional showers this weekend may lead to additional discharges and this event is considered ongoing. 

The cause is believed to be a combination of heavy thundershowers and debris blockage at the outfall. This same outfall was the site of a 13 minute overflow on February 8 that cleared itself. 

A combined sewer overflow is about 80% stormwater and 20% sanitary sewage. Because of increased bacteria in the water from the sewage, the public is advised to avoid contact with the Willamette River in the area north (downstream) of Willamette Park for 48 hours after the CSO event ends. Environmental Services will update the public when the overflow stops.

Since completing the ratepayer-funded $1.4 billion Big Pipe project in 2011 to eliminate most but not all overflows, about 94 percent of CSOs to the Willamette River have been eliminated and 99 percent to the Columbia Slough. Both the river and slough are much healthier for recreation and for wildlife. State and city officials determined that reaching 100% CSO control would not significantly
improve river health while doubling the costs to ratepayers.  Find out more about CSOs, what they are and why they occur at:

The Bureau of Environmental Services works with Portland residents and businesses to protect water quality, public health, and the environment through wastewater collection and treatment, sewer construction and maintenance, stormwater management, and stream and watershed restoration. @besportland

Media contact: Diane Dulken 503.823.6742.