Mother Nature dumped more than three inches of rain in Portland in since Friday.

For a change, that didn’t result in any flooding of Johnson Creek or sewage discharges into the Willamette River.

In past years, a tenth of an inch of rain in a 24-hour period would cause the city’s combined sewer and stormwater system to overflow, dumping untreated sewage into the Willamette River. But the city’s $1.4 billion Big Pipe system and related stormwater improvements kept the river free of such discharges, according to the Bureau of Environmental Services.

“The last few days of heavy rains tested our system, and I’m pleased that it worked exactly as it was designed to,” said City Commissioner Nick Fish, who oversees the BES.

The tunnel system installed as part of the Big Pipe project filled to about the 50 percent capacity on Saturday and was up to 83 percent on Sunday, handling the surge in runoff without spilling any sewage into the river system.

The BES completed the Big Pipe system in late-2011.

Last year, the agency formally opened the new Foster Floodplain Natural Area to the public. It was the culmination of a multi-year project to acquire land and relocate homes so Johnson Creek could expand into its historic floodplain without inundating residents living close to the creek. That provided enough flood storage capacity to cover the 63-acre area with two feet of water.

Johnson Creek, which once flooded about every other year, held steady this time. Engineers estimate the creek will still overflow about once every six to eight years.

But not this time.

Steve Law can reached at 503-546-5139 or This email address is being protected from spambots. You need JavaScript enabled to view it..

Twitter: @SteveLawTrib

Follow Sustainable Life at