Heavy rain causes sewer overflow to the Willamette River

Combined Sewer Overflow (CSO) Advisory
Heavy rain causes sewer overflow to the Willamette River

December 4, 2014

A rainstorm on Thursday, December 4, 2014 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 until mid-afternoon on Saturday, December 6.

The combined sewer overflow event began just before 2:00 p.m. on December 4 and ended later that afternoon. As a precaution, the public should avoid contact with river water for 48 hours after the combined sewer overflow event ended.

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 within 48 hours of a CSO event should wash their hands following contact with river water. Those who choose to eat fish caught in the Willamette River within 48 hours of 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 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.