Current Water. Green Stormwater Infrastructure. Seattle Space Needle from ferry.

Green Stormwater Infrastructure: What is Seattle doing?

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2nd in a series

Green Stormwater Infrastructure: 700 Million Gallons project

In 2012 Seattle launched the ambitious “700 Million Gallons” project.  The goal is to manage 700M gallons of polluted runoff per year by 2025 through the use of Green Stormwater Infrastructure (GSI).

Rain gardens, bioswales, planter boxes, rain barrels, cisterns, green roofs, permeable pavement and new trees are included as part of the GSI solution.

The GSI solutions are intended to mimic the processes found in nature that have been lost due to removal of pervious surfaces.

Details on the program, including a city-wide map showing the location of hundreds of GSI installations already operating, diagrams, tips and tools, and rebate information can be found on the 700MillionGallons.Org website. 

GSI funding help through RainWise rebates

Seattle Public Utilities (SPU) and the King County Wastewater Treatment Division (WTD) partnered to create a program called RainWise. Residents that live in targeted sewer-overflow basins may be eligible for rebates to hire trained RainWise contractors to install rain gardens or cisterns on their property.

RainWise is available to 50,000 properties in the Seattle area. The City of Seattle and King County may pay up to 100% of the installation cost of rain gardens. Nearly 1,200 rain garden and cistern projects on private property have already been funded, with an average rebate of $4,000. These rain gardens represent 18 million gallons of water that is managed annually and the volume keeps growing.

Green Stormwater Infrastructure examples around town:

Rainwater Harvesting: Stack House Apartments

The Stack House Apartments in Seattle are utilizing cisterns in a Rainwater Harvesting program that captures and holds 42,700 gallons of runoff from 20,250 square feet of roof area. This water is then used to meet all of the irrigation requirements for the property. Not only does this system help prevent flooding but it reduces the amount of water drawn from the municipal water supply for irrigation.

Current Water. Green Infrastructure. Stack House Apartments, Seattle, WA
Stack House Apartments, Seattle, WA
Current Water. Green Stormwater Infrastructure. Stack House Apartments. Seattle WA
Rainwater Harvesting data at Stack House Apartments, Seattle, WA

Rain Barrels: Cascade P-Patch Community Garden

In the Cascade neighborhood forty-eight 55-gallon rain barrels collect and store 2,640 gallons of rainwater from an adjacent flat roof. This rainwater is filtered through sand, charcoal and limestone filters and then released back into the community garden for irrigation resulting in water savings.

Current Water. Green Infrastructure. Cascade P-Patch Rain Barrels.
Rain barrels at Cascade P-Patch, Seattle, WA
Current Water. Green Infrastructure. Cascade P-Patch.
Cascade P-Patch. Seattle, WA

Biofiltration Swales, Diversion Vault and Swirl Concentrator: Swale on Yale

The Swale on Yale project includes four biofiltration swales along Yale Avenue North and Pontius Avenue North. Two swales were completed in 2013 and the remaining two are slated for completion by 2018.

The swales measure approximately 270′ long and range in width from 10.5′ to 16.5′ wide, depending on their locations. The swales will contain grasses to slow the flow of stormwater and filter out pollutants before the water reaches the lake.

A large underground diversion vault captures the runoff and then directs it back into the bioswales. Garbage and debris will be “spun” out by a “swirl concentrator”, captured in a sump, and then collected by SPU employees.

Current Water. Green Infrastructure. Swale on Yale.
Swale on Yale, Seattle, WA

Marine Habitat Protection: Salmon-Safe

Salmon-Safe was created to certify farms that support good land-use practices that protect salmon. Now the program has expanded to include urban construction sites, wineries, breweries, urban campuses, airports, and hospitals.

The Salmon-Safe certification process goes beyond basic GSI. On urban construction sites SS addresses stormwater management (capturing pollutants), water use management (efficiency), erosion management and sediment control (prevent and capture), pesticide reduction and water quality protection (eliminating poisons), and enhancement of urban ecological function (protecting wildlife habitats).

Seattle Children’s Hospital is the first Salmon-Safe certified hospital in the nation, Seattle-Tacoma Airport is the first certified airport in the nation, Redhook is Puget Sound’s first certified brewery, and Vulcan Real Estate is the world’s first Salmon-Safe accredited developer.

Current Water: Green Infrastructure. Salmon-Safe.
Salmon-Safe mesh construction-site banners for Vulcan Real Estate, Seattle, WA
Current Water. Green Infrastructure. Water filtration on Vulcan Real Estate site, Seattle.
Water filtration tanks in use on Salmon-Safe Vulcan Real Estate site. Seattle, WA.

Green Roof: Zoomazium at Woodland Park Zoo

Guests at The Zoomazium at Woodland Park Zoo may not realize that they are standing beneath an 8000 square foot green roof. It isn’t just a lawn up there either. The green roof uses specially formulated light-weight soil and includes a variety of flowers, ferns and grasses that are native to the Pacific Northwest.

The Mithun Landscape team carefully selected the plants. Mithun also worked on the design for the beautiful Brightwater Wastewater Treatment Center in Woodinville, WA.

The green roof can improve stormwater management by reducing runoff and improving water quality, conserve energy, increase longevity of roofing membranes, reduce noise and air pollution, sequester carbon, and increase urban biodiversity by providing habitat for wildlife. And on top of that, it’s beautiful.

Current Water. Green Infrastructure. Green Roof.
Zoomazium Green Roof. Woodland Park Zoo, Seattle, WA. Photo from Zoo.Org.

Seattle is recognized as a national leader in the implementation of Green Stormwater Infrastructure. The 700M Gallons Project is on track for success having almost reached the half-way point of its intermediary goal of 400M gallons by 2020.

The alternative to using cost-effective GSI is to build more wastewater treatment plants. King County’s newest plant, the Brightwater Wastewater Treatment Plant in Woodinville, WA, cost a whopping $1.8B. Seattle is hoping to avoid more costs like that.

By: Jennifer Croft


For more information:

700 Million Gallons in Seattle, click here

2016 Overview and Accomplishment Report for Seattle’s Green Stormwater Infrastructure, click here

LEED certified Stack House Apartments, click here

Cascade P-Patch, click here

Swale on Yale, click here

Swale on Yale and it’s connection to Salmon-Safe, click here

Salmon-Safe, click here

Zoozamium green roof, click here

Mithun and the Brightwater Center, click here

Green Infrastructure: The Basics click here