PORTLAND, Ore. (KOIN 6) — A brief but intense rainstorm Monday afternoon caused Portland’s combined sewer system to overflow to the Willamette River.
According to an advisory, combined sewage overflowed through an outfall pipe near the Morrison Bridge on the east bank of the river shortly after 4 p.m. and lasted for about 12 minutes.
As a precaution, the public is advised to avoid contact with the river from the Morrison Bridge downstream to the Willamette’s confluence with the Columbia River near Kelley Point Park until Wednesday afternoon.
The Bureau of Environmental Services recommends these precautions to protect public health.
Combined Sewage Overflows (CSO) are contaminated with bacteria from untreated sewage.
Portland’s combined sewer system carries sewage and storm water runoff in the same pipes. During very heavy rainstorms, the increased storm water 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 reduced Willamette River CSO events from an average of 50 per year to no more than four per winter and one every third summer.