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Earth & Sky :More Info About Natural Drainage Page 2 of 9 So it's slightly different from the SEA Street? DA: No, the SEA street project was our Flrst test street, and that was a case where we basically redesigned the whole street right-of-way to accommodate these open wetland swales that's where the storm water goes, and that's where it has an opportunity to infiltrate back Into the ground. The way we traditionally do drainage in the past is that we basically transferred the problem of storm water from point A to point B. Usually that means you're just trying to move It out of the street right-of-way quickly, and it almost always winds up in a water body, whether It's a creek or Puget Sound, or one of the lakes there. So not only Is it a problem for water quality, because you have the storm water picking up pollutants from the street right- of-way and being sent directly to the water bodies, but the giant volumes of storm water that's generated from streets and all of [he Impervious surtaces like driveways and homes, these large volumes of storm water, when they are transferred quickly to our creek systems, makes for impossible conditions for all [he creek's biota salmon, bugs, everything else [hat's In there to live. So the goal of these projects are to reduce that total volume, reduce the amount of water that actually gets transferred there, and really, the only way you can do it are two ways; one is to hold it indefinitely in a large pond and not even release it. Or you can infiltrate it back Into the ground. Now here in the city, It's a very urbanized environment. We don't have giant ponds where we can just hold storm water Indefinitely. Our goal is to do basically what nature did with storm water in the Flrst place, which is to put it back in the ground. SG: Going back to the SEA project, can you give us abefore-and-after snapshot of that neighborhood? What were the original features and how were they modified? DA: The original [SEA] street in this area of the city was not formalized, so it did not have sidewalks, it did not have traditional drainage infrastructure. But it was pretty much Just achip-sealed street that ran the full right-of-way from property to property. SG: A chip-Fllled street? DA: A chip-filled street is a kind of aloes-budget way to make a hard surface. So this was not an improved right-of-way. A large area of our city is like this because these were areas annexed late In the city's history. So they have been gradually undergoing Improvements, bringing in of course drainage infrastructure. Now when you bring drainage infrastructure, unlike In the years past, you have to put In water quality and detention facilities along with that streetscape. When you looked down the street before, it basically had no definition. People would just park all over. And it really was wall-to-wall impervious surface of the street, the chip-filled street. What we did is we removed a lot of the impervious surface. We narrowed [he roadway, much narrower than you would build for your usual city code for the street, which is pretty standardized across the country. We put in one sidewalk, and we curved the roadway in order to provide enough space to put in these large swales, and also to slow traffic. And now, the swales are depressions in the ground that are heavily amended with composted soil. And there's [he sponge factor that holds on to [he storm water and allows it to infiltrate into the ground to the harder soils underneath. Then it's heavily planted, over a hundred trees and thousand shrubs. http://earthsky.com/shows/showsmore.php?t=20041103 I 1 /8/2004