Big Pipe reaches 10-year milestone; new online tracker lets public see in real-time how Willamette River stays sewage-free

Press Release
A decade of data show how Portlanders’ investment in the Big Pipe system is working to send sewage and stormwater to the City’s treatment plant and make overflows rare. The new Big Pipe Tracker lets the public see the system in action.

As the Big Pipe Project reaches its tenth year in operation, Environmental Services today announced an online gauge that lets the public track in near real-time how the system keeps sewage out of the Willamette River. In the rare occasions when an overflow occurs, the gauge also allows the public to track an incident’s start, stop, and duration.

GIF showing levels in the Big Pipe changing from 26% to 44% to 51% to 46% during a storm last November.
This animated graphic shows Big Pipe levels during a storm last November, during a test period for the Big Pipe Tracker. The graphic is updated every 15 minutes, with a lag time of less than 45 minutes.

Environmental Services also released ten years of data showing how the project is achieving its design goals of reducing overflows by 94 percent, making combined sewer overflows to the Willamette River rarer, shorter in duration, and lower in volume. The payoff, since project completion in 2011, is a healthier, cleaner river.

“On this ten-year milestone, I am pleased to bring a new tool for transparency – a way for the public to see how the system works in close to real time,” said Commissioner Mingus Mapps. “The Big Pipe is making a big difference for Portlanders and our relationship to the Willamette River. River recreation has soared as more people are boating, playing, swimming and enjoying the river, and for good reason – the river is cleaner.”

The Big Pipe Project is shorthand for an ambitious set of actions and improvements, including two giant pipes that line the east and west banks of the Willamette River in Portland, that together eliminated most combined sewer overflows, or CSOs.  

“Overflows are now dramatically fewer, shorter, and smaller,” said Environmental Services Director Michael Jordan. “Ten years of data show how Portlanders’ investment in the Big Pipe system is working. The new Big Pipe Tracker shows the system in action, so keep refreshing your browser during rainstorms and see how the city is sending sewage to the plant and keeping it out of the river we love.”

The gauge, or Big Pipe Tracker, shows a circular graphic with markers from zero to 100 percent, representing the levels of sewage and stormwater that fill two giant pipes on both sides of the Willamette River. Instead of overflowing to the river, treatment plant operators store, monitor, and direct the flow to the City’s main wastewater treatment plant in North Portland.

An accompanying chart tracks flows during a 72-hour period. Data are updated every 15 minutes, with up to a 45-minute time delay. In the rare event that the pipes exceed capacity and an overflow occurs, Environmental Services will issue an advisory. 

Environmental Services’ ten years of data shows how rare those 

Chart showing actual overflows over ten years - a low of one and high of seven
Ten years of data show overflows ranging from seven to one - down from over 50 per year before the Big Pipe

occurrences are, and that incidents are fewer, shorter, and smaller in volume. Before the project  completion in 2011, it didn’t take much rain to cause an overflow—only about one-tenth of an inch, which is a regular day of rain in Portland. Today, it takes about ten times that amount of rain to come close to reaching an overflow.

  • Fewer: Portland experienced a high of seven overflows per year (in 2017) and a low of one per year (in 2019 and 2020). Before the Big Pipe, overflows occurred about 50 times a year, often for days at a time. Since completion, the average number of incidents has been 3.3 per year.
  • Shorter: Overflows are now about four hours on average, down from 42 hours on average. The last two overflows, in September this year, lasted about 10 minutes and 20 minutes each.
  • Smaller: The volume of overflows has decreased by about 95 percent per incident, from an average of 6 billion gallons to 297 million gallons. Overflows are about 80 percent stormwater and 20 percent sewage.
Chart showing overflows fewer (down from 50 to 3.3 average), shorter (down from 42 hours to 4 hours on average) and smaller (down from 6 billion gallons to 297 million on average)
Overflows are now fewer, shorter, and smaller.

While the Big Pipe system is named after its main features—the two giant pipes on either side of the river and one along the slough—the $1.4 billion project that spanned 20 years to build included many other engineering upgrades and additions. Those include  green street planters and rain gardens, which continue to be installed today, and a Clean River Rewards program that continues to encourage homeowners to disconnect downspouts and let rainwater soak into the ground instead of adding volume to pipes Follow the tracker at  Find out more at


The City of Portland Bureau of Environmental Services - your sewer and stormwater utility - provides Portland residents with programs to protect water quality and public health, including wastewater collection and treatment, sewer construction and maintenance, stormwater management, and stream and watershed restoration. Follow on Twitter - @BESPortland. On the web: