Weekend of January 15 - 18, 2016
Lots of rain but no combined sewer overflow (CSO)
During the rain storm from January 15 to January 18, 1.7 inches of rain fell in Portland. Rain was generally heaviest in northwest and south Portland.
Wastewater Collection and Treatment
The Columbia Boulevard Wastewater Treatment Plant normally processes an average of 70-million gallons a day. On January 17, the plant processed 239.8-million gallons.
The plant processed a total of 697.1 million gallons from January 15 to January 18. That's enough water to fill nearly 22,500 railroad tank cars.
You can monitor rainfall across the city along with the treatment plant's control center team. Environmental Services posts rain gauge data at City of Portland HYDRA Rainfall Network.
One inch of rain within 24 hours can be enough to cause a combined sewer overflow to the Willamette River. Rainfall during this storm did not exceed that level and the Willamette River big pipes safely conveyed all the wastewater to the treatment plant. There was no overflow to the river.
At the peak of the storm, the 16-foot diameter West Side Big Pipe and the 22-foot diameter East Side Big Pipe together reached only 30% capacity, storing about 307 million gallons of wastewater, a combination of stormwater and sanitary sewage, and conveyed it all to the Columbia Boulevard Wastewater Treatment Plant.
With every inch of rain, Portland's 1,700 green street planters collect and filter about 3.8 million gallons of stormwater runoff, and allow water to soak into the earth to replenish groundwater.
During the January 15 - January 18 storm, green streets managed more than 6.4-million gallons of stormwater.