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Celebrating RainWise pollution prevention milestones in the King County basin

By October 25, 2021June 13th, 20232 Comments
A woman stands next to a home cistern to show it's scale - it's almost as tall as she is

As the days get shorter and we anticipate more rain in our forecast, we are celebrating a timely milestone—we just mailed our 1,000th RainWise rebate check in one of the eligible combined sewer overflow basins!

Our utility strives to prevent pollution from entering our local waterways, and one way we are doing this is through the RainWise program. RainWise provides rebates to eligible private property owners that install rain gardens and/or stormwater cisterns. RainWise rebate checks are paid out to these property owners because they are installing green stormwater infrastructure systems at their homes, businesses, schools, and other community gathering spaces and capturing rooftop rainwater runoff on-site rather than sending it directly to the sewer. RainWise is offered in neighborhoods that are part of the combined sewer system where stormwater pipes and sewer pipes connect to larger pipes heading to the treatment plant. During heavy rains the increase in stormwater overwhelms the pipes and cause the system to overflow into the nearest body of water.

With 1,000 RainWise installations in King County controlled basins, a lot of the stormwater that would have entered our regional sewer system is now being captured and slowed down by cisterns or soaking back into the ground after being diverted to a rain garden.

We want to thank all of our RainWise property owners who are part of this solution for managing rainwater runoff as we celebrate this milestone. This collective effort manages the rain that falls on 1.24 million square feet of roof area, almost 29 acres, in King County neighborhoods subject to combined sewer overflows.

And that is only in King County basins! RainWise is a joint program offered by both King County and Seattle Public Utilities (SPU). Both utilities are responsible for different combined sewer overflow basins. SPU started the program in 2010 and we joined them in 2013. Together, the program now captures runoff from over 2.85 million square feet of impervious surface, over 65 acres. This results in over 29 million gallons of rainwater runoff kept out of the sewer system annually.

The RainWise program is just one part of both utilities’ strategies to reduce the number of combined sewer overflows. Reducing the amount of stormwater runoff into Seattle’s sewer system has only grown in importance as local populations and impervious surfaces, like rooftops, parking lots, and roads, continue to increase. Because these overflows include polluted runoff and sewage, they pose a risk to public health and the environment.

“RainWise proved to be a great solution to our landscape challenges while simultaneously helping regional storm water problems.”

  – Dave Kregenow, RainWise homeowner & recipient of 1,000th King County rebate

RainWise rain gardens and cisterns do more than reduce overflows in the sewer system. They also provide amenities for property owners and landscapes. They can help control drainage issues, provide nature and beauty for people and pollinators, and cisterns can provide a source of summer water when not needed for stormwater control.

Think you may live in an eligible neighborhood an interested in becoming a part of the solution? Visit to find out if the home you own or rent qualifies, watch webinars, upcoming webinars, learn more about the program’s environmental benefits, and discover how to participate in “contractor matchmaking” process that connects homeowners with contractors available to start your RainWise project!