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Big Rainstorm Results in Little Sewer Overflow

This storm is a striking example of how well the Big Pipe project has worked.

Portland’s respite from apocalyptic weather news continues: The deluge of rain that hit the city last weekend produced little flooding and only one, local overflow of sewage into the Willamette River.

The second combined sewage overflow of the year occurred early Saturday morning, shutting down part of the Willamette River for recreational use due to the dangerous bacteria that can be found in the sewage system. But you probably weren’t planning on a swim at that time: The overflow lasted from 1:30 to 1:40 am near the St. Johns neighborhood in North Portland.

The volume of the overflow is not currently known, says the Portland Bureau of Transportation, which prior to the cold front had issued pleas for residents to unclog their storm drains.

The first large rainfall of the season typically carries three concerns: floods, sewer overflows and landslides. But Hannah Schafer of PBOT says Portland had “no reports [of flooding] that rose to the level of anything major.” She knew of no landslide reports, either.

The limited scale of problems stemming from the storm is thanks in part to the Big Pipe project. That sewer overhaul, completed in 2011, has decreased the number of overflows to the Willamette River by 94%. When once there was an average of 50 overflows a year, there is now an average of only four every rainy season and one every three summers.

This storm is a striking example of how well the Big Pipe project has worked. One-tenth of an inch used to be enough to cause sewer overflows. This storm consisted of 2.45 inches of rain, more than 20 times that amount, and only caused one overflow.

“Our investments are working,” says Diane Dulken, spokeswoman for the Portland Bureau of Environmental Services. “The river is clean enough to swim and play most days of the year.”