FEATURE ARTICLE: Stormwater Systems in Urban Environments

The recent changes to Seattle’s Stormwater Code have added one more hurdle to an already challenging course. Our civil practice talks designing for urban spaces, navigating the Department of Ecology’s new requirements, and Seattle’s Green Stormwater Infrastructure (GSI) standouts.

Department of Ecology Guidelines – What’s All the Fuss About? 

The Puget Sound region continues to struggle with water quality, even as stormwater regulations increase. Released this October, The Seattle Times article, “Stormwater Pollution in Puget Sound Streams, Killing Coho Before They Can Spawn,” points to the issue’s reach and reveals what a priority it is in the region. The salmon are dying, and the same contaminants continue to damage the Puget Sound, affecting everything from orcas to oysters.

To protect, preserve and enhance natural resources, the Department of Ecology’s Stormwater Guidelines continue to evolve. The most recent guidelines put more emphasis on Low Impact Development (LID) or Green Stormwater Infrastructure (GSI) – think rain gardens, rainwater harvesting, sustainability efforts, etc. In 2016, the State Department of Ecology and local jurisdictions (including the City of Seattle) adopted a more restrictive drainage standard related to GSI, strictly interpreting the guidelines. Where previously GSI was encouraged, it is now required.

What Does this Mean for Projects? 

The City of Seattle began enforcing this additional requirement immediately at its release, in January 2016, changing the way we execute local projects. In this new setup, projects must explain why they can’t apply the city’s preferred (sometimes unattainable) GSI approach. The explanation must be in-depth, with specific cost details from the building team. For example, a team may propose bioretention planters in place of the city’s rainwater harvest and re-use system.

Implementing GSI strategies into tight sites and urban environments is challenging, as there are very few places to incorporate the systems. At urban infill projects, additions like green roofs and rainwater harvesting systems become expensive quickly. Add the new layer of regulation complications, and urban projects could quickly become the things of nightmares.

However, we’ve recognized that by carefully coordinating elements that were already planned for projects and making early changes to how roof drainage was managed, we can bypass the more difficult and costly systems while still achieving the positive goals of GSI and aligning with requirements.

Green Stormwater Infrastructure (GSI) / Low Impact Development (LID) 101

Let’s go back to basics. Green Stormwater Infrastructure (GSI) systems are designed to mimic natural drainage patterns and treat our Earth’s resources with care. Our civil engineers regularly design creative GSI systems for sites in the Pacific Northwest, everything from green roofs and rain gardens to stormwater re-use and bioretention systems.

Stormwater management is especially relevant in the Pacific Northwest for two reasons. First, the culture. Locals sincerely care about sustainability efforts and hold businesses, municipalities and themselves accountable. Certifications like Salmon-Safe and regulations like the GSI ordinance were created because the community demanded them. Second, there’s simply a lot of water here. Natural drainage patterns differ from region to region, and there are special considerations for the Pacific Northwest’s zone. The amount of water and the resources affected by it make stormwater management critical for our fragile natural systems. In the Seattle area alone, resources to consider include rivers, salmon populations, and groundwater. Looking at the context of the Pacific Northwest may help us understand why the Department of Ecology continues to enhance the requirements for stormwater.

What Are We Doing Differently?

When the new requirements were first implemented, they wreaked havoc within the project process. Plumbing design didn’t occur until the later stages of the design process, but now, to appease requirements, teams had to modify previously approved roofscapes, or put thousands of extra dollars toward plumbing systems and design redo costs.

What do we recommend? Align the team – everyone from architect and owner to the civil engineer and plumbing consultant. Create the drainage plan early so the team can make decisions against code requirements and ensure no opportunities are lost. Consider the roof and the roof drain plumbing system an integral part of the stormwater approach and permitting process. Leverage your civil partner’s experience and expertise. Prioritize GSI, avoid steep redesign costs and potential project delays.

So, what has the last year taught us? Put simply: Plan for GSI early. Instead of considering GSI a last-minute add-in, it must be prioritized. The requirements disrupt the traditional design process. Now, teams must enter the schematic design phase knowing what the plumbing system and landscaping areas on and/or next to the building can do.

What do we recommend? Align the team – everyone from architect and owner to the civil engineer and plumbing consultant. — Tim Brockway, Senior Civil Project Manager

Best Practices

Urban environments undoubtedly complicate things, and with the added challenge of meeting the state’s requirements, it’s more important than ever to meet challenges head on and adhere to best practices when designing and implementing stormwater systems.

1.  Marry the Science with the Story.
As with all design decisions, the incorporation of a GSI system must be purposeful. Ensuring stormwater system innovations complement programming can be a challenge, but the payoff is a functional, differentiated project with a strong story and identity.

2.  Commit to Coordination.
Most GSI plans affect every discipline: landscape, civil, architectural, structural, plumbing, construction. And they require sign-off from municipalities. Coordinating among so many parties requires proactivity, clear communication, and quite frankly, a time commitment. Civil engineers, who are traditionally responsible for managing the GSI plans and process, especially need to prioritize collaboration and understand the responsibility they’re shouldering.

3.  Maximize Space.
The less space, the more puzzle-like the project. In urban settings, there’s less space overall, so bioretention-over-structure designs (stormwater systems integrated into a building’s footprint) need to be adapted to tight areas.

4.  Communicate Value. 
“If a tree falls in a forest and no one is around to hear it, does it make a sound?” The challenge with GSI systems is to ensure that they, as the metaphorical fallen tree, make a sound. It’s important to communicate value (what you did and why it matters) beyond the project team to the community, thereby raising awareness, crediting your project partners, and ultimately, attracting tenants.

5.   Exceed the Requirements. Development in the Pacific Northwest can be challenging enough as it is. The recent changes to the stormwater code have added one more wrinkle to this already tricky terrain. Strive to create unique systems and solutions, so instead of only satisfying regulations, systems are designed to add value to the project beyond just meeting the code. It’s important to partner with team members who understand the challenges, are adept at navigating jurisdictions and municipalities and have a strong portfolio of work from which to draw inspiration.

Adapting Stormwater Systems for Urban Environments: The Showstoppers

What happens when best practices are applied? These PNW projects converted challenges into opportunities with sophisticated GSI systems and strategies.

Walton Lofts

Located in Belltown, Walton Lofts symbolizes a convergence of style, sustainability and premium downtown living. Walton’s location along the Growing Vine Street watershed and street park served as inspiration and allowed the team to explore designs not typical for the area or multi-unit residential designs.

What makes it a GSI standout: Quite a few things – a block-long swale collects, treats, and then gently guides water toward Elliott Bay and seamlessly integrates with the neighboring P-Patch. It earned three Green Globes, and overall, is a brilliant example of sustainability merging with urban environments.

Project team: Architects: Shoesmith Cox ArchitectsVIA Architecture, Owner: The Schuster Group, Structural Engineer & Civil Engineer: Coughlin Porter Lundeen, General Contractor: Turner Construction, Landscape Architect: Kenneth Philip Architects

Read our article, “Growing Vine Street”
Visit growingvinestreet.com

Fire Station 20

The Fire Station 20 team created a model of sustainability in an industrial neighborhood, achieving LEED Platinum certification by incorporating solar panels, green roofs, geothermal wells, and LED lighting on a sensitive, steeply-sloped urban site.

What makes it a GSI standout: A gray water reuse system captures and stores shower water in a large cistern, allowing it to be recycled onsite – perfect for washing fire trucks! Retaining walls prevent erosion of the 30-foot slopes and integrated, tiered rain gardens treat and manage stormwater runoff. Water and energy savings are communicated to the community via signage and a custom flip-dot display just outside the building.

Project Team: Architect: Schacht Aslani Architects, Owner: City of Seattle Fire Department, Structural Engineer: Swenson Say Faget, Civil Engineer: Coughlin Porter Lundeen, General Contractor: FORMA Construction Co., Landscape Architect: Nakano Associates

Fire Station 20 Sustainability Brochure

Terry Avenue Building

Terry Avenue Building was rehabilitated and incorporated into Amazon’s South Lake Union campus. Originally constructed in 1915, it now houses three Tom Douglas restaurants and is flanked by Amazon’s Dawson and Ruby office buildings.

What makes it a GSI standout: First, Terry Avenue Building’s GSI system is celebrated as a design element as stormwater is collected and flows through a tiered planter alongside the staircase. Pedestrians and passersby interact with it daily. Second, and just as notable, is the efficiency born from a creative approach to GSI. When the site plan closed groundwater flow, our team developed a unique overflow system that rerouted trapped water to free-flowing areas. This solution was applied to multiple projects in the area, simplifying design challenges and allowing more efficient building layouts across the campus.

Project Team: Architect: Callison, Owner: Vulcan Real Estate, Structural & Civil Engineer: Coughlin Porter Lundeen, General Contractor: GLY Construction, Landscape Architect: Walker Macy


The Roosevelt District’s Eleanor is a two-building apartment complex featuring 270 units with floor-to-ceiling windows and open floor plans. Outside, a boardwalk and greenscape separate the two buildings while creating a unique community outdoor gathering area. Green features include solar panels, sun shades, and easy access to public transit.

What makes it a GSI standout: The site is an old creek bed, which inspires the entire design. A rooftop rainwater collection system feeds the courtyard rain gardens with exposed downspouts and runnels, enhancing functionality of the site’s wetlands and the stream beneath the boardwalk. It’s not only an impressive stormwater mitigation system, but a part of the building’s identity.

Project team: Architect: Runberg Architecture Group, Owner: Mack Urban, Civil & Structural Engineer: Coughlin Porter Lundeen, General Contractor: Compass General Construction, Landscape Architect: Hewitt  

Visit eleanorapartments.com

We love seeing projects in Seattle succeed and believe that with the right process and proactivity, every project can. We’re honored to be a part of our city’s continued growth, in GSI and beyond. To learn more about Coughlin Porter Lundeen’s sustainability efforts and vision, click here.