Green Infrastructure Can Help Save Our Salmon


Salmon are a cornerstone of our cultural identity in Seattle and the Pacific Northwest. Salmon are vital to our economy, our environment and our sense of place. The health of our native salmon runs has been identified as an indicator of the overall health of Puget Sound and local streams. Scientists have been researching the connection between declining salmon populations and urban stormwater pollution. These scientists have discovered a major threat to the health of our salmon but they have also discovered a simple solution that mitigates the impacts 100% of the time.

As our human population grows, so does the magnitude of pollutants released into our waterways. Large quantities of contaminants such as metals, petroleum-derived compounds like oil, grease, vehicle exhaust, and detergents accumulate on our roadways and parking lots where there is no absorption. Every time it rains, these containments are washed directly into storm drains and into our creeks, lakes, the Duwamish River, and Puget Sound. Researchers have now found a direct link between polluted urban stormwater runoff and salmon mortality.

A recent straightforward study exposed salmon to stormwater runoff from a local highway.  In every case, the salmon died within 4 to 6 hours. The conclusion was clear: stormwater pollution is lethal to salmon. However, the study also tested a potential solution. When researchers first filtered the highway runoff through a column filled with a soil mixture and then exposed the salmon to this cleansed water, they survived 100% of the time.
Filtering water through a living, plant-soil system is the basis for green stormwater infrastructure (GSI). The City of Seattle has listened to the science and determined this is a direct influence we can have on Puget Sound. By using GSI we can help to improve water quality and prevent more contaminants from reaching our waterways. For this reason, we have set an ambitious goal to accelerate the use of green infrastructure in our city and are also supporting regional green infrastructure efforts.

The Washington Nature conservancy created a great short video highlighting this research. You can find the video at

For more information on the research:

For more info on what the City of Seattle is doing with GSI visit our webpage:


Online Resources, Photos and Talks from GSI Summit

This past February the City of Seattle was pleased to join Stewardship Partners, The Nature Conservancy, Washington Environmental Council, Washington State University, MIG-SvR Design, Boeing, Vulcan, and many other collaborators and sponsors to co-host the first Puget Sound Green Infrastructure Summit.

Resources, photos and talks from this Summit are now available on-line at:

Green Stormwater Infrastructure – A Key Tool to Cleaning Our Waterways

Green Stormwater Infrastructure (GSI) is a term being used more frequently in Seattle and the Greater Puget Sound area—and that’s a good thing. GSI is the use of natural drainage systems like rain gardens and cisterns to slow, capture, and clean polluted runoff before it harms our lakes, rivers, and streams. By mimicking the way forests manage rainwater, GSI also brings natural beauty and a host of other benefits to our neighborhoods and homes.

The science is clear:  polluted stormwater runoff from our roads and roofs is the greatest threat to water quality in Puget Sound and directly endangers our salmon populations. But by using green infrastructure, together with other smart urban strategies like street sweeping and forest protection, we can prevent this pollution and provide broader community value.  It’s a true win win.

That’s why Seattle has deepened its commitment as a national leader in this area by setting a goal to manage 700 million gallons of polluted runoff  with GSI annually by 2025. We’re committed to using natural approaches to manage stormwater wherever we can, because we know these approaches protect our waters and make our neighborhoods better.

In order to help catalzye innovative partnerships and accelerate GSI implementation across Puget Sound, the City of Seattle is pleased to join with Stewardship Partners, The Nature Conservancy, Washington Environmental Council, Washington State University, MIG-SvR Design, Boeing, Vulcan, and many other collaborators and sponsors  to co-host the first Puget Sound Green Infrastructure Summit.

The Summit will take place Feb. 24th from 9 am to 4:30 pm at the Mountaineers Club, and will bring together diverse leaders from government, academia, business, and non-profit organizations from across Puget Sound.  Participants will  map the strategic role of green infrastructure in our cities, towns and communities and in Puget Sound’s clean water future.

For more information visit:


Reducing water pollution with green approaches

Polluted stormwater runoff is the leading water quality threat to Puget Sound, the City has released a draft citywide Green Stormwater Infrastructure Strategy, outlining plans to accelerate green approaches for preventing this type of water pollution.

Rainfall rushing off hard surfaces like roads and parking lots can overwhelm our piped drainage system and cause back-ups and combined sewer overflows. The runoff also carries pollution directly into creeks, lakes, and other waterways. Green stormwater infrastructure (GSI) prevents overflows and pollution much like a forest would – by slowing and cleaning the water, and either reusing it or allowing it to soak back through the soil. Examples of GSI include roadside bioretention swales and street trees that manage street runoff; raingardens and cisterns that manage roof runoff; and green roofs and permeable pavement that are self-managing.

The draft Strategy sets an interim goal of managing 400 million gallons of stormwater runoff annually with GSI by the year 2020, summarizes progress to date, outlines a set of strategies and planned investments for accelerating the adoption of GSI in Seattle, and articulates a two-year work plan for City of Seattle departments.

The draft 5-year GSI Implementation Strategy is available for public comment through August 26. For more information, contact Pam Emerson, Green Stormwater Policy Advisor,, 206.386.4507.

Submit comments electronically here.

SEPA Decision for Low Impact Development Code Changes

DPD has completed the SEPA review of the proposed low impact development (LID) code changes. DPD has also updated the LID website has been updated to include links to the LID ordinance/code amendments, Director’s Report, SEPA Decision, and the SEPA Checklist.

Low impact development is a stormwater management strategy that mimics natural processes to reduce the amount of rainwater that runs off a site. LID strategies include bioretention (a process that removes contaminants from stormwater), reducing impervious surfaces, or clustering buildings together to reduce site disturbance.

In undeveloped areas, most precipitation soaks into the ground, evaporates, and/or is absorbed by plants, and very little rainfall becomes surface runoff. The natural water cycle relies on plants and infiltration to manage stormwater, replenish groundwater, and maintain water levels in streams and rivers. Developed areas with pavement and rooftops have much more runoff, less infiltration, higher risk of flooding and water quality issues, and greater fluctuation in stream and lake levels.

DPD has reviewed all land development rules and has proposed code amendments to remove any barriers to low impact development and to encourage LID where appropriate. These amendments are a requirement of the City’s municipal stormwater permit from the Washington State Department of Ecology.

Our proposed amendments increase flexibility for certain low impact development strategies in a broad range of zones and development types. They generally fall into one of two categories:

  • Modify existing language to remove barriers to implementing low impact development (e.g., landscaped areas must be protected, not enclosed by a curb or barrier)
  • Encourage low impact development by listing it as a public benefit item or broadening a term to include LID strategies (e.g., allowing bioretention to count towards amenity area requirements)

Currently, property owners can install cisterns in yards and setbacks, where appropriate. Our proposal also makes it clear that applicants can install features like rain gardens and other green stormwater infrastructure features where landscaping is required, such as in surface parking lots and residential or commercial amenity areas. As these low impact development strategies become more common and familiar, it is important the City’s land use regulations do not inadvertently prohibit this best practice.

None of our proposed changes require an applicant to implement low impact development. The Stormwater Code is the regulatory document that outlines stormwater management requirements. Furthermore, the proposed amendments do not prohibit any action or development that is currently permitted under the Code. Our proposed amendments support the City goals for managing stormwater with green stormwater infrastructure.

If you have questions regarding the proposed LID code amendments please contact:

Maggie Glowacki
(206) 386-4036

Nick Welch
(206) 684-8203