The beautiful weekend may have already erased memories of last Thursday evening’s downpour, which resulted in stormwater flowing down the streets and some trees to crash down on Forest Park’s Lower Macleay trail. But here’s a great piece of news: in the past, this type of rain storm would have filled the city’s sewer pipes and caused an overflow of combined sewage into the Willamette River. This time, that didn’t happen.
Thanks to Portland’s investment in fixing combined sewer overflows (CSOs) with upgrades to our sewer infrastructure, the river and Columbia Slough are cleaner and safer for people and fish. The CSO control program included constructing the big pipe, disconnecting downspouts, and building green street facilities to manage the rain naturally. Portland’s combined sewer system used to overflow an average of 50 times a year. Now, those overflows rarely happen. Learn more in a video about the CSO program here.
In the last two years since the big pipe was completed, there have been only five overflows to the Willamette River. There hasn’t been a significant combined sewer overflow to the Columbia Slough since 2000.
The wastewater engineers and operators at Environmental Services work 24-7 to keep the sewer system pumping and treating sewage and stormwater. Thursday and Friday, they kept right up with the storm, and the big pipe got only 87% full. Our green infrastructure, like street trees and rain gardens, also does its part to keep a lot of stormwater out of the system and save ratepayers money. This big storm dropped an average of 1.25 inches of rain on central Portland in 12 hours, but no sewage spilled in to the river. That’s something we can all celebrate! While we are paying off the construction costs of the combined sewer overflow projects for several more years, it’s important to remember that this infrastructure will be working for clean rivers for many decades to come.