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Portland, Ore. (Pamplin Media) — Heavy overnight rains in Portland and the vicinity led the Big Pipe sewage draining system to reach capacity in containing combined stormwater and sewage. An overflow to the Willamette River began about 3:15 a.m., Monday, Jan. 3, and is ongoing.
Additional heavy rain is forecast for later this week and a city of Portland advisory is extended through Sunday, Jan. 9. People are encouraged to avoid contact with river water downstream of the Ross Island Bridge during the advisory.
During an overflow, and for 48 hours afterward, the public is advised to avoid contact with the river because of increased bacteria in the water. During all other times, the river’s water quality is safe for recreation.
The public can track Big Pipe levels with the city’s new online tracker.
A combined sewer overflow is about 80% stormwater and 20% sewage, according to the Portland Bureau of Environmental Services. Such overflows now are rare and can occur during periods of heavy rain or snowfall. This is the third event since November.
Since completing the Big Pipe project — the 20-year, $1.4 billion program to reduce overflows — in 2011, the number of overflows has dropped by 94% to the Willamette River and 99% to the Columbia Slough, according to the city. Before the project, overflows occurred to the Willamette River from multiple outfalls an average of 50 times per year, with some instances lasting days.
Today, overflows occur an average of four times per winter season and once every three summers.
Find out more about the Big Pipe and overflows at the website.