The Capitol Hill Water Quality Project bioswale in South Lake Union (Image: PG Psomas)

Even if the weather has been atypically dry lately, we all know this is Rain City. Seattle rain usually comes as a drizzle that we shrug off without an umbrella (actually, I love my umbrella and I’m not ashamed). But that doesn’t mean we don’t have plenty of it and that it needs to go somewhere.

We all know that water travels downhill because of, well, gravity. When it rains in a forest, a prairie, or even a wetland, water tends to move slowly to lower ground and eventually some sort of basin like a creek, wetland, river, or lake. When rain falls on paved city streets, on the roofs of buildings, and on our many parking lots, it has nowhere to go because it can’t penetrate and seep into the soil. Intentional and functioning designs in urban spaces direct water to places where it can drain away instead of sitting in place. The simplest place to send that water in an urban space is into a series of pipes that lead into a nearby waterway. In the case of the Hill that’s through drains that run into Lake Union, Lake Washington, and eventually Puget Sound.

This might seem innocent, but the stormwater that flows off our pavement and makes its way to the saltwater is the source of 75% of the pollution in the Sound. Heavy metals like copper from car breaks, high loads of bacteria and fertilizer from our lawns, polycyclic aromatic hydrocarbons from vehicle combustion, wood stoves, and more, all taking a ride in stormwater. Just one acre of impervious surface like concrete can funnel a million gallons of polluted water into local waterways annually.

Unfortunately, on top of this, much of the stormwater infrastructure in and around the Hill is pre-Clean Water Act. It would never be allowed to be built today because it doesn’t do a great job of slowing and cleaning dirty water. Much of Capitol Hill still has large runs of combined sewer drains, where both stormwater and sewage share the same drain. This was an economical choice that worked better when we had less people, less impervious surfaces, and there were lower chances of the system being overwhelmed. Today, whenever these drains overflow, which happens during big rain events, we get raw sewage escaping where it’s meant to go – into the West Point Treatment Plant in Discovery Park and other more local systems.

The orange lines on this clip of the SPU Water and Sewer Map are combined sewage and stormwater drains. We have a lot across the Hill. (Credit: Seattle.gov)

The good news is that we have solutions that are simple and effective at collecting, slowing, and filtering stormwater (even if combined drain systems are harder to replace). Individually, homeowners can install cisterns to store water on their properties for watering their garden or take it a step further and install a rain garden that funnels water through swales and demands far less clean, municipal drinking water to keep healthy and beautiful. Planting more trees, which can take up tens to hundreds of gallons of water every day depending on size and species, is also a simple technology available to us. (However, maintaining existing healthy trees and greenspaces is far more important than replacing them.)

Part of the challenge is that our rapidly growing region has been losing tree cover and green spaces in the name of progress – soil is being paved over rapidly. Thankfully, because of the Clean Water Act and the requirement for National Pollutant Discharge Elimination System (NPDES) permits when new and redevelopment happens, there are baselines for how stormwater is handled. Depending on the scope of the project, developers may be required to treat water on site, create a retention pond (think of those ponds at on and off ramps around I-5), develop swales, or some other approved method of handling stormwater.

Likely unbeknownst to you, there has been a stormwater technology testing facility in North Lake Union since 1996. The Lake Union Ship Canal Test Facility is owned by the Washington Department of Transportation and is operated by the Washington Department of Ecology in collaboration with the University of Washington. This facility, which drains about 32 acres of land (23 acres of pavement and 9 acres of roadside landscaping) is directly under I-5 and was built to test and approve emerging stormwater technologies for use in Washington State. A NPDES permit holder needs to use a technology that has been tested and approved in the Pacific Northwest, and this facility is one of the places companies offering technologies can get verified for use. Four separate tests can be in operation at once at the facility and there is typically a waiting list to get in.

The Lake Union Ship Canal Test Facility under I-5. (Image: The Washington Stormwater Center)

I like knowing that this sort of testing facility exists, and it’s fun knowing that it’s in our backyard. But I also like knowing that simple solutions like swales and rain gardens can help make our ultra urban spaces healthier. A suite of solutions are being implemented all over our region and close to home – there’s the Swale on Yale that handles 435 acres of Capitol Hill drainage and treats around 190 million gallons of stormwater annually. Green infrastructure like the Madison Valley Stormwater park can combine much needed outdoor spaces with ecosystem services that are vital to continuing to live in a functional urban environment.

Make no mistake, bioswales and other green infrastructure are highly engineered and require our tinkering and input. But they are way more compelling and have far less environmental impact to build than, say, the giant ship canal stormwater tunnel that runs between Wallingford and Ballard. While certainly vital, it will also cost around 700 million dollars when completed and is made of cement (because it’s impermeable). Closer to home, many of us are familiar with the closures due to building of the G Line Rapid Ride on Madison, a thing we should be proud of because it’s better public transportation combined with stormwater holding tanks that reduce the stress on the combined sewer lines in the area. Yet, I can’t help but think solutions oriented in the power of plants and the natural filtration of soils feel a bit more compelling and romantic to me than a bunch more cement to deal with the problems created by impervious cement.

A map of imperviousness in Seattle created using The Nature Conservancy’s Stormwater Heat Map. Any green on the map represents impervious surfaces and the lighter colors represent permeable surfaces (which is why Washington Park Arboretum fades into the same color as the water). West Capitol Hill into South Lake Union and Downtown has a lot of impervious surfaces – which should be no surprise. (Data Credit: stormwaterheatmap.org Map Credit: Brendan McGarry)

Either way, what’s still alarming is that the crap stormwater pulls into our waterways isn’t decreasing. There are more cars than ever on our roads and the projections are for more traffic, not less. Cars are the primary source of stormwater pollution (yes, getting rid of cars sounds like a good solution), and impervious surfaces aren’t going anywhere even as local communities try to move toward softer, more permeable built environments. These problems are bad for humans, the health of iconic Pacific Northwest species like salmon and orcas, and are not a good look for a region that prides itself on connections to the natural world. The good news is that there are many smart people on the job – trying to understand the true utility of green infrastructure, what pollutants are the worst offenders, and continuing to push the status quo ( and thanks to orgs like Puget Soundkeeper Alliance there are watchdogs outside local government too).

Late last year, I had an evening on foot getting from the Seattle Waterfront up to the Hill. It was a soggy day and I was glad for that umbrella and waterproof shoes because of all the standing water I had to slog through. While a bit of me wondered what contaminants I was tracking home, I also couldn’t help but note how many places have started to shift during my life in Seattle. While development might be increasing impermeable surfaces, and traffic might be on the rise, there were also more rain gardens than I even remembered as I submitted the Hill. Of all the environmental problems we face, stormwater is one we can tackle without getting overwhelmed and even in some cases we can do it in style, developing places that improve other aspects of our lives at the same time. Maybe I’m naively optimistic but in this case, I think I am okay with that.

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