Portland, Ore., achieves one year without sewage overflow into local river

According to OPB News, Portland, Ore., celebrated a notable achievement this week when it reached one full year with no sewage overflows into the Willamette River.

Portland is one of about 800 U.S. cities with a combined sewer system — meaning stormwater and sewage move through the same pipes. During high-rain season, the system sometimes is inundated and overlows into the city’s riverway.

In 2011, the city of Portland completed a $1.4 billion, two-decade sewer overhaul project known as the Big Pipe Project, which has significantly reduced the number of overflow incidents. Even with the system improvements, however, overflows can still happen up to four times during a typical rainy season, OPB News reported.

Before the infrastructure upgrades were completed, sewage overflowed into the river an average of 50 times annually, according to the Portland Bureau of Environmental Services.

The bureau estimates it would have spent twice as much money on a system that stopped overflows entirely.

As part of the Big Pipe Project, Portland installed three new pipes with diameters measuring up to 22 ft. that could handle larger water inflows.

The bigger pipes have allowed the city to take in more sewage. The bureau is now expanding its wastewater treatment facility on Columbia Boulevard, a $515 million project.

Portland previously achieved a full year without overflows when it went 499 days without overflows between August 2019 and December 2020.

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