To prevent the death of endangered salmon in Lake Washington from toxic stormwater pollution, the Data 1 mixed office and retail building in Fremont Seattle, WA will divert water from the Aurora Bridge on State Route 99 into a series of bioretention cells in their landscaping. This helped win Salmon Safe certification and a Master Use permit in 2016.
Research has shown the immediate effect of polluted stormwater runoff on salmon, resulting in acute chemical exposure which kills fish in a short period of time (J. McIntyre, 2015). This project capitalized on a new development standard to address stormwater pollution with green infrastructure. Permitting followed the Design Review Board process with public discourse but few complications. Developers maximized building volume for the parcel and earned the Master Use permit through the innovative public benefit service of diverting polluted stormwater from the overhead State Route 99’s Aurora Bridge to bioretention cells on their private property.
By demonstrating the design in good faith with the Seattle Stormwater Code, the City of Seattle granted a permit to connect the Aurora Bridge’s drainage system with the designed bioretention cells. Additional permission was required from State transportation officials to access the water from the bridge, and also to modify the effluent into a Federal waterway. These tiered rain gardens are designed to filter 200,000 gallons of water per year. Other building features complied with local requirements, and a public comment period tuned design features to improve neighborhood character. Public education signs throughout the site will describe how the tiered rain gardens filter stormwater toxins to benefit salmon.
State Environmental Policy Act requires "Determination of Non-Significance", (DNS) issued if officials determine there will be no probable significant adverse environmental impacts Data 1 complied with SEPA regulations by demonstrating compliance with the Stormwater Control Manual and incorporating a green roof and the engineered rain garden featured in this study.
Seattle Stormwater Code requires projects to meet the requirements of the City’s Non-Point Discharge Elimination System permit (NPDES) The permit was issued by Seattle to the property owner to divert stormwater from the overhead highway to the landscape feature as part of the effort “liberally construed to accomplish” environmental remediation in Seattle.
The rain garden system is a series of seven planted cells, separated by metal weir walls, linked by perforated culverts which drain the water from one cell to the next to maximize filtration and soil saturation. Each box measures 200-300 square feet and is filled with river rocks and engineered soil medium to create a natural stream bed effect. Plants were selected for drought tolerance, hardiness to toxins, soil stabilization characteristics, and aesthetic appeal.
The bioretention cells slow and clean the water as it approaches the Fremont Cut waterway, and allows sediment and metals to settle into the treatment cells rather than washing directly into the waterway. Reduction in turbidity has been shown to be critically beneficial for aquatic species downstream. Each cell can treat more than 80 gallons per hour, with a cumulative treatment capacity of more than 600 gallons per hour. Over a year, the bioretention cells will treat 200,000 gallons of stormwater runoff.
The rain gardens provide enough capacity and treatment potential to reduce water pollution from storm events, and the overhead bridge creates a shady space where the water is able to cool on its way to the Fremont Cut, where temperature sensitive fish live. This simple and small opportunity to slow, clean and soak into the soil mitigates immediate lethal impacts affecting fish populations.
To enhance the impact of this innovation, developers include signage for the garden to boost awareness among passersby. In addition to the bioretention rain garden, the green roof feature also helped Data 1 meet Salmon Safe requirements.
Salmon Safe Certification is a popular credential for developers in the Seattle area. Prescribed construction and utility practices must comply with environmental building codes governing British Columbia, Washington, Oregon and Northern California. The core categories for Salmon Safe urban development are stormwater management, water use management, erosion prevention and sediment control, chemical and pesticide reduction and water quality protection, and enhancement of urban ecological function.
Data 1’s rain gardens service one of Seattle’s busiest highways, and water quality studies showed runoff from the SR-99 bridge as particularly polluted. Developers learned of the impact roadway toxins have on aquatic populations and saw their development as an opportunity to address water quality in the Fremont Cut and create a functional landscape feature.
Underway in September 2017, Data 1 will provide nearly 120,000 square feet of retail and office space, part of Tableau Software’s expansion adding more than one million square feet of office space in four buildings in North Lake Union and Fremont, just a few miles away from their previous headquarters in South Lake Union. Inspired by a nearby award-winning building - the Terry Thomas - Data 1 incorporates many people-friendly features: naturally lit office space with windows for every room, ground level retail and a plaza for pedestrians, a bicycle entrance with indoor storage and shower room, a green roof and rooftop gathering area. Unique features of Data 1 include a piece of the Berlin Wall and commissioned artwork to enhance sense of place, and the landscape feature highlighted in this report.
The change in location to the suburban neighborhood north of the ship canal, adjacent to transportation amenities such as the Burke-Gilman Trail and SR-99, benefits the commuter culture for Tableau. While the company gains some breathing room from contemporary giant Amazon.com and others, they remain close enough to continue a neighborly business culture.
The innovative rain garden design went through the City of Seattle permitting processes earning public support along the way. This began with an Early Design Guidance meeting for public input on neighborhood impacts as required by the Seattle Land Use Code. Early plans included a plaza area for pedestrian traffic and incorporated this activity area with the rain gardens. These public, pedestrian-oriented features and the educational aspect helped the project earn support from the Design Review Board, helping to build enthusiasm for the project moving forward. After several reviews and public comment periods, the Building Permit was issued October 2015.
Data 1’s feature is one of 12,000 rain gardens throughout the Seattle area being constructed this decade. It is the first of a series of rain gardens in the Fremont neighborhood which will annually filter 2 million gallons of rainfall from the northern half of the SR-99 bridge before entering the Fremont Cut waterway. Seattle administrators are eager to address storm water pollution as each local certified Salmon Safe project improves the ecosystem downstream. This project is an early demonstration of a major quality improvement in surface water runoff from roadways and a significant step to addressing the crisis of stormwater pollution in Seattle, COU LLC streamlined the permitting process on Data 1 with progressive stewardship.