Earth & Sky

Background:

In 2000, the Seattle Public Utilities Department began construction on a pilot project to reconstruct two city blocks using new technology to reduce storm water runoff.

The effects of storm water runoff, especially after a torrential downpour, is harmful to aquatic life. The rain washes pollutants from hard surfaces like roads that eventually ends up in lakes, rivers, and bays. On its way there, large volumes of fast-moving storm water causes significant erosion to creeks and destroys its aquatic wildlife.

The Street Edge Alternatives (SEA) project was a new way to redirect rainwater falling on impervious surfaces directly into the ground, keeping it out of creeks, ditches, and storm drains. Rainwater seeping into the ground is naturally filtered by the soil to remove heavy metals and other pollutants, resulting in cleaner water entering aquifers, lakes, streams, and bays. In addition, the absence of fast high-volume storm water runoffs preserves creek ecosystems.

On the street that was part of the SEA pilot project, rainwater was directed into depressions along both sides of the street that contained composted soil, and was planted with water-tolerant plants. These “swales”, as they’re called, act like mini-wetlands, holding the rainwater to let it percolate into the ground and be absorbed by plants. If rainfall is heavy, the swales, which are connected to each other, are able to overflow from one to the other to redistribute the water load.

This project turned out to be extremely successful; it was able to reduce storm water runoff by 98% at the two reconstructed city blocks. As a result, a new initiative called Natural Drainage Systems has been started to adapt the same technology to other areas of the city. An overview of that initiative, as well as information on individual projects, can be found at the Seattle Public Utilities Department

Interview with Denise Andrews, Surface Water Program Manager
Resource Planning Division, Seattle Public Utilities.

SG:
What kinds of projects do you have in the works right now?

DA:
We’re just completing a 15-block area that has two separate prototype streets. Both of these streets are using natural drainage systems. What that means is that instead of transferring the storm water through a series of pipes and walls, what we do is we try to instead infiltrate that storm water back into the ground, wherever it’s falling within the street right-of-way.

SG:
So it’s slightly different from the SEA Street?

DA:
No, the SEA street project was our first 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 the impervious surfaces 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 the creek’s biota – salmon, bugs, everything else that’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 first place, which is to put it back in the ground.

SG:
Going back to the SEA project, can you give us a before-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 a chip-sealed street that ran the full right-of-way from property to property.

SG:
A chip-filled street?

DA:
A chip-filled street is a kind of a low-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 the 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 the sponge factor that holds on to the 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.

SG:
When you talk about it being heavily planted, this is in the 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 in, 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 them 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 how 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 it’s about 660 linear feet. And a typical city block is about 330 ft. 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. You’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 a marsh-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 slowly. But they’ve found that these are very ineffective just because of the size of [the ponds], the fact that they’re rarely maintained, and it’s a very centralized way to manage the storm water.

So we pretty much took an idea that we’ve seen applied in very suburban areas on the east coast, and we just decided to try it in a very urban setting, which of course, came with a large degree of design issues to work out. But it was just so successful in the monitoring and the protection of water quality, and the reduction of flow that it just became a no-brainer to use in more residential areas. Now they’re very urban areas but they’re still single-family residential areas. You have a lot of room to utilize the right-of-way. Now we may have to go in an area that gets a lot denser, like downtown areas or industrial areas, where we may have to go to different techniques, alternate storm water techniques, such as rooftop gardens or something, to be able to apply the same science.

SG:
How much maintenance is required for these swales?

DA:
The first 3 years is very critical. The first 3 years, you want to establish the plants by getting them watered, and picking the weeds out. And so far, we have great homeowner participation. The folks who live on the street are asked to do the watering and to do the maintenance which is extensive those first 3 years, and I mean extensive…. it’s like anyone who puts in a new garden, you want to water it and keep the weeds out until the plants get established so they don’t need so much watering, so they fill out across the soil, which makes it hard for weeds to come in. We’ve had great participation by citizens. The SEA Street, I believe, it only had about a 2-3% plant failure, which is pretty remarkable for the amount of plants that went in. So it’s very participatory. It’s not something the city alone can do, we can’t just pay for that kind of maintenance so citizens have to participate and the design actually helps because it’s so integrated with their front yards, it is like an extension of their front yards. So people have a tendency to want to make it look nice. It very much blurs the line between private and the public space.

SG:
These swales actually hold the water until it slowly percolates into the ground?

DA:
Right. Except when the storm level gets too high, then they can overflow to the next swale, and ultimately, the whole system has the ability to overflow into the street right-of-way exit when the storm is much too high for the ability of [the swales] to hold all the water. So there are cases in very large storm where it will overflow….

SG: …. so it will use the old storm water access?

DA:
Once [storm water] leaves the area … it’s like, you know, small wetlands filling up and spilling over into the next one, and to the next one, so they follow a course until the whole system can no longer absorb the storm water, and then it will flow off this area into the areas that were existing [before, with no swales], and those usually have areas of improved ditches along the right-of-way.

SG:
How do you go about selecting the vegetation, do you test them out, do you use native plants?

DA:
We use a lot of natives, but not exclusively. We have a really great landscape architect who works for the city, and she’s been doing the SEA street program and right-of way program for a long time so she has a lot of experience with these plants. We also, on the streets, in order to have folks in their homes be very interested in caretaking, we have a program where they help pick the plants, so that it’s more customized to what they like. We certainly use a lot of natives, especially in places where maintenance is not going to be that easy to do because we don’t have that many homeowners on that one block. And there we would pick just very hard-core native ones … once they’re established you just can’t kill it, you don’t have to water it, you don’t have to weed it, once they’re established they can live on in perpetuity. But along some of the streets, folks are choosing non-natives to make the whole planting more attractive; folks are engaged in taking care of it.

SG:
One thing I noticed about the curvature of the roads … is that just a design to increase the swale areas or was there another reason, besides slowing traffic as well? It looks unusual.

DA:
Yeah, you were correct. The two reasons were both to give us flexibility in where to place the swales because we have to work around people’s driveways, or we work around the trees that we, of course, don’t want to take down. But we also know that by narrowing the roadway and curving it, you also slow traffic, which was a very big problem in these neighborhoods. We had received a lot of complaints about how fast people drive on these streets. This is where people live and work, and walk and have their kids playing, so they were very interested in slowing traffic.

But we did find that after we built it, people just really liked the aesthetics of having the curves to the streets, and they feel safer and more attracted to the street so the streets are now attracting people from the wider neighborhood who, when they want to take a walk, they immediately aim for these streets because they feel so… they’re so aesthetically good to walk on.

SG:
When you direct water back into the ground, do you have to deal with basement flooding issues?

DA:
Oh, that’s a good question. At first we weren’t sure what was going to happen once we started infiltrating. But we had a great storm just this past year … we had just gotten the swales and the soil in before winter on this one street. One side of the street is a hillside – not a steep hillside but a slope to the street so there were folks whose homes were actually below the grate of the street on the downhill side. And what happened on October 20, 2003 was we had the hundred-year storm come through. We had about 5 inches of rain in 24 hours. Of course we all ran out to the street to see how it was doing, and it looked like it was working well, but I still wasn’t sure. But the next day we received a phone call from a gentleman who lived on the downhill slope and he said, “What did you do? My sump pump has gone off in my basement for the last 25 years in any kind of rain, and this is the first time it didn’t go off.” In other words, there was no water in his basement for the first time. So we obviously intercepted the storm water from running onto his property, it infiltrated [into the ground] and it did not affect his basement, it actually solved his problem. That’s when I finally gave in and said, this must work!

SG:
In the beginning you mentioned that this program is now called the Natural Drainage Systems program and there is a 15 blocks area with two separate prototypes of drainage being designed. Could you speak a little bit about these new developments? So far, what we’ve talked about was mainly SEA Street.

DA:
We have another very large project that’s part of a very large redevelopment in an area that was for low income housing, and there … they are completely redoing over a 100 acres to make it higher density. We worked with the developers, the housing authority early in the process to try to apply this natural drainage system to the site because it eventually drains into one of our premier salmon bearing [creeks] here in the city. And our goal was to not … you know, if we did traditional storm water [drainage] it really wasn’t going to help this creek and in fact it would probably make it worse, since more impervious surfaces and higher density was going into this neighborhood.

SG:
Which creek is this?

DA:
Longfellow Creek in southwestern Seattle. The site is now under construction but what we basically applied was about a 32 block area of natural drainage systems, and we did it in a way where we could still follow the architect’s guidelines for more traditional-looking streets. We keep trying to stretch our imagination and stretch what we can do technically with each project we take on.

We weren’t sure if we could do it with the traditional curved system of the street but we found ways to send the water into grassy areas that aren’t heavily planted, grass areas that are going to be used, actually, as open space where kids could play, because we were so limited in the amount of space we had to work with. So it doesn’t have to have that heavily vegetated look to it to be successful.

We did achieve the objectives for water quality and for addressing and infiltrating storm water that we were looking for over this area. So that really bumped it up to another order of magnitude in working with this whole area. And I think ultimately, if we can do that, if we can retrofit an existing urban city … I think that this just clearly shows that areas that are developing farmland and forest into suburban developments, this so more clearly applies … it will be more cost-effective to just do it correctly the first time at a lower cost to the developer and at a much higher [level of] environmental protection.

SG:
I’m trying to get a better grasp of this new program. It’s in a new development area for low-income housing and you’re trying to accommodate it into a more traditional-looking neighborhood. How long has this particular project been in place for?

DA:
It’s been in planning for a few years. The construction just began this past spring; so it’s basically … they’re still in the part of the construction where they’re deconstructing the whole 100-acre area. Everything’s going, the house, the roadways, so it’s a multiyear process. It’s probably the largest and last major redevelopment within Seattle. You’re just never going to find that much space ever again for a redevelopment. There were three major low-income housing areas in the city and all three have been redeveloped to become denser and to upgrade the housing. This was the final one and we got in on the ground floor just in time to be able to implement the natural drainage systems with the developer.

SG:
What are your plans for the future?

DA:
We are trying to institutionalize this approach to managing storm water within the city and that means redefining our storm water codes and our building codes. We’re hoping to be able to make it such an integrated part of building … especially when you’re in a creek watershed, there just really no other choice to be had. That’s how you would develop your right-of-way. Mostly we’re focusing on the public right-of-way because that accounts for about 25% of our city’s landscape.

SG:
When you talk about right-of way, you’re talking about roads?

DA:
Yes, roadways.

25% of the city landscape is obviously a lot of space and it’s space that the city does have some control over unlike private property. Now that doesn’t mean that we’re not going to now explore what folks could do on private property.

The future will lean towards having new technology for larger areas that are more commercial and industrial. So in other words, you’d have in an industrial area, a typical building is … you could have an acre of roof on a building that’s really only one story high because it’s a storage or warehouse building. So you’ve got a tremendous amount of impervious surface and yet you’re trying to pack a lot of industrial use in the area. We may have to go to new technologies like applying green roof technology. I think parking lots are another great place to start applying the natural drainage system concepts of infiltration.

We’re testing a couple of streets in the High Point project, about 3 city blocks of porous roadway pavement, not just the sidewalks but the actual driving lanes with porous asphalt. We’re testing new technologies, we’re trying to institutionalize the approach through the building code and storm water code, and we’re trying to export the information – we think this is really important because we share these water bodies together and we have lots of Clean Water Act regulations and we’re trying to help jurisdictions around us learn about what we’re doing and hopefully apply some of these techniques to areas they are developing … why make some same mistakes that we made a hundred years ago? It’s just not necessary anymore.

SG:
I live in Baltimore, and one of the problems we have … like we have in most large cities, is funding. A lot of times, the immediate infrastructure needs take precedence, the old Band-Aid fix to something. How do you go about selling an idea like this to your city council?

DA:
Especially in older cities, the right-of-way, at some point, the old infrastructure needs to be replaced, and typically, you’ll have a street ripped up … and instead of putting back the street as we used to think of it, especially in residential areas, you can basically put a different kind of infrastructure back, in this case, a natural infrastructure that’s more sustainable in the long run, and actually costs less money, and provides all these other community benefits that we hand not counted on in the first place which is the livability issue and the greening of the city streets. People’s perceptions of safety and community… these are all benefits to be gained by any city whether they’re redeveloping because it’s time to change out the infrastructure, or new cities that are expanding.

SG:
Would this cost more, than say the traditional…

DA:
No. Actually, we’ve been watching the costs very closely and the highest cost to doing a typical street construction is the cost of concrete. These are very expensive materials. Our streets are gaining higher levels of water quality compliance and detention compliance at a lower cost because, instead of now having to put a large water quality underground vault into the street, your water quality requirements, which most cities and state have to do now through the Clean Water Act, they can basically put in vegetation and soil which costs a lot less. So our streets are actually costing 1/4 to 1/3rd less to meet the same environmental … to meet or surpass the environmental protection requirements.

SG:
Is there anything else that you’d like to add that I may not have thought about asking?

DA:
I think that there’s going to be a real movement towards sustainable infrastructure happening in this country, maybe we’re some years ahead of our time here. But I think, especially for people who are going into engineering fields, this is a new and exciting place to look. Just like in the old days, people used to learn to build dams. Well now, they’re going to school and learning how to deconstruct them. So I think the future is looking towards what nature does well, and learning to not try to overwhelm nature with engineering but to do what she does very well and try to mimic those functions. Even though we may never mimic or replace that forest that was once here when we built the city, we may be able to mimic the function that nature had done for us, and I think its an exciting new field for those folks who are in school now or thinking about a new career.

The following person was interviewed for today’s program. Our thanks to:

Denise Andrews
Surface Water Program Manager
Resource Planning Division ,
Seattle Public Utilities
Seattle, WA