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Earth & Sky :More Info About Natural Drainage Page 3 of 9 SG: When you talk about it being heavily planted, this is in [he garden areas around the house? DA: Oh, even in the bottom of the swales. We use different kinds of plants. We use the more water-tolerant plants in the bottom of the Swale, and as you go up the sides of the Swale and all the areas around it, the objective here Is to try to create as much absorbent vegetation and soil surface as possible. So when you look down the street, now that It's grown fn, It's very lush, It's very inviting to people who want to walk through the area. SG: According to your website, this ran about $850,000? DA: That was the very first prototype street. Now we're building [hem less expensive and of course when you're building 15 blocks, It's less expensive than one block. So a lot of those [SEA project] costs went Into actual studies and communications with the neighborhood. The cost of the streets are less expensive now. They're about depending on the type that you build, the same street would cost between $500,000 and $700,000 depending on haw many features you want to put in. And that's actually two typical city blocks together; it's called a superblock because the streets are actually two blocks long. So ft's about 660 linear feet. And a typical city block is about 330 ff. We usually count the SEA Street as two blocks. We have monitored our streets for several years now. And the reason why we've moved so quickly, expanded the program so quickly, was based on the result. The SEA street project reduced the runoff from that street by 98%. And that was in some good-sized storms as well. Vou're gaining water quality to that level as well because that water is not leaving the street. Any pollutants from runoff from that street Is being trapped in the soil. Things such as heavy metals, which are typically very deadly in aquatic environments for fish and other creatures, is being trapped in the very top centimeters of the soil. Now it's not remediated, it stays there but at least it's in a place that can't do very much damage like it can In an aquatic environment. Other major pollutants, such as the oil runoffs from cars, are carbon based and when It's not overloaded Into the soil system, it can actually be remediated through the microbes in the soil. SG: In the original SEA project, what percentage of impervious surfaces were taken out? DA: The right-of-way was about 100% Impervious. We reduced the overall impervious surface if you were going to Just put in the street and two sidewalks, I believe, we reduced it quite a bit, down by about 20-25% from its original which was 100% Impervious. So there's still a roadway, there's still driveway access and parking, and one sidewalk instead of two. But even by Just reducing it 20% Impervious, it's the system of moving the storm water Into these hugely vegetated Swale soil systems [where] you make that kind of gain. SG: How did you get the idea of using the swales? It's a really cool idea because you're almost mimicking amarsh-like area. DA: That's right. It's been around for a while, mostly on the east coast. People have actually utilized them a little bit in very suburban environments, and we actually now manage storm water across the country by sending storm water to these large ponds. Well, the ponds are still in use across the country in more suburban areas as well, and they are supposed to mimic the marshes, or a place where the water can either infiltrate or Just be released more http://earthsky.com/shows/showsmore.php?t=20041103 11 /8/2004