January 15, 2016
Some facts about how Portland’s sewer and stormwater infrastructure performed in recent heavy rains.
During the storm event that began on January 11 and ended on January 14, 2.4 inches of rain fell in Portland. Rain was generally heaviest in north and northwest Portland. One rain gauge on Sauvie Island recorded a little over three inches.
Wastewater Collection and Treatment
The Columbia Boulevard Wastewater Treatment Plant processed an average of 177 million gallons per day during the four-day storm. The largest daily volume was 282.4-million gallons on January 13. The treatment plant normally processes an average of 70-million gallons a day.
The plant processed a total of 708.32 million gallons from January 11 to January 14. That's enough water to fill more than 1,073 Olympic size swimming pools.
You can monitor rainfall across the city right along with the control center team at the Columbia Boulevard treatment plant. 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 intensities during the January 11 to January 14 storm exceeded that level, but the Willamette River big pipes safely conveyed all the wastewater to the treatment plant and there was no overflow to the river.
At the peak of the storm, the Willamette River tunnel system reached 35% capacity. The East Side and West Side Big Pipes stored about 250 million gallons of wastewater and conveyed it 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 11 - January 14 storm, green streets managed more than 9.1-million gallons of stormwater.