12/05/2023 | Press release | Distributed by Public on 12/06/2023 10:36
With a series of atmospheric rivers coursing through the Portland area this week, the City of Portland Bureau of Environmental Services data show that the Big Pipe system has so far prevented multiple combined sewer overflows (CSOs) to the Willamette River.
The Big Pipe Tracker has shown four spikes so far during this storm system. Each spike represents sewage mixed with rain that the Big Pipe system intercepted and prevented from overflowing to the river. BES operators instead store the mixture in two giant pipes on either side of the river and then direct that flow to the City's main wastewater treatment plant in North Portland.
BES estimates that since Sunday, the Big Pipe system has prevented more than 300 million gallons of diluted sewage from reaching the river.
The public is encouraged to follow the Big Pipe Tracker for the remainder of the storm, and during future storms. As long as the gauge is under 100%, the river continues to be sewage-free. If an overflow occurs, the gauge will reach 100% and BES will issue a news advisory shortly after.
A CSO is about 80% stormwater or rain, and 20% sewage.
Before the Big Pipe system was completed in 2011, overflows occurred almost every time it rained, an average of 50 times a year, with some overflows lasting days. Today, CSOs are rare. The number of CSOs has dropped by 94 percent to the Willamette River and 99 percent to the Columbia Slough.
About Environmental Services
Environmental Services - the City of Portland's sewer and stormwater utility - protects public health and environment by collecting and recovering resources from the city's wastewater, managing stormwater, and restoring and protecting Portland's rivers, streams, and watersheds.