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Thread: Rain gardens/bioretention swales and space

  1. #1
    Cyburbian
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    Rain gardens/bioretention swales and space

    The concept of using rain gardens and bioswales seems in so many ways simple, yet why haven't there been more of this used in best practices management with stormwater management. Bioretention areas could be used in places where there is a parallel parking space - changes to a small garden or bed that retains stormwater runoff containing pollutants, sediment, debris and other harmful chemicals that make their way to local rivers, creeks and streams.

    I make a serious effort to push these devices and methods in my area. However, as it is all known, if it doesn't benefit the developer then it can often be a wasted breath. Until it's mandatory I'm still going to pursue proper environmental methods in containing runoff. In a recent story on NBC, Chicago has made strong efforts toward developing rain gardens on roofs and become active within its streets and roadways to contain runoff.
    Last edited by Crabkey; 01 Jun 2007 at 2:39 PM. Reason: spelling

  2. #2

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    I'm unfamiliar (although I'd like to know more) about rain gardens / bioswales / green roofs, etc... If a green roof is designed specifically for run-off collection, (as say, designed to cool the building) does that preclude its use as active space?

    At the moment, we award additional FAR for incorporating green roof features. Naturally though, developers should be incorporating such features without a carrot...

  3. #3
    Cyburbian Tide's avatar
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    Simple, in this age of litigation it's a maintenance issue and no one can agree on how to keep them maintained. Also, it costs more than digging a hole in the ground to let the water leak out slowly.
    @GigCityPlanner

  4. #4
    Cyburbian wahday's avatar
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    Swales are used fairly regularly in my parts - New Mexico. I see them a lot in newer, large scale parking lots and especially on National Forest land as a way to control runoff and erosion on unpaved access roads. Also along the highways and some major roads, especially at complex interchanges where runoff has been dramatically changed and redirected. By and large, these are just filled with rip rap and so aren't really bioretention swales filled with vegetation to clean water of pollutants, though.

    I did propose this very design (bioretention swales) in a project for a part of the city/county area that has no sidewalks and will not build them until storm sewers are installed which the county expects will be in about a decade. The idea was to establish an unpaved (or perhaps poly paved or crusher fined) "sidewalking path" separated from the roadway by a swale (at present, the streets in this area are crowned and so water runs into the unpaved shoulders and s-l-o-w-l-y percolates. This means kids must walk in the middle of the street to get to school after a rain). The residents were very excited about the idea, but City engineers thought they had a better idea - a 3/4 million dollar project to establish a storm sewer system that would collect water in a temporary holding pond and then pump this a quarter mile to a second, more adequate pond on land that they were "hoping" to purchase form a private owner. And this was to address the problem on only one street. My project area was dealing with about 25 streets in an area around an elementary school. Crazy.

    Being a high desert, we also have some unique water runoff challenges that are very distinct from other places I have lived. In general, our natural surfaces (not to mention paved ones) are fairly impermeable and so when it rains, we can get some dramatic flash floods and quick accumulation that is beyond what the (limited) storm sewers can accommodate. In some areas, following heavy rains, the street itself IS the designated storm runoff channel, moving water downhill to a retention pond. You can imagine the trafic problems this creates. Last summer, we got caught in one of these areas. We literally floated a few times and water was pouring in under the doors. The big local story, though, was the guy that abandoned his pickup, but left a window down (why he did this in the rain, I don't know). The news showed the water reaching the top of the door and then spilling into the truck. Major bummer.

    One cool thing they have been doing in the outlying semi-urban areas is to establish surge pods that are also parks with playing fields. The water overflow is pumped into the retention pond/athletic field with a slight (barely noticeable) grade. So, the storm water overflow ends up watering the fields - its really rather elegant and simple.
    The purpose of life is a life of purpose

  5. #5
    Cyburbian Big Owl's avatar
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    Quote Originally posted by Crabkey View post
    The concept of using rain gardens and bioswales seems in so many ways simple, yet why haven't there been more of this used in best practices management with stormwater management. Bioretention areas could be used in places where there is a parallel parking space - changes to a small garden or bed that retains stormwater runoff containing pollutants, sediment, debris and other harmful chemicals that make their way to local rivers, creeks and streams.

    I make a serious effort to push these devices and methods in my area. However, as it is all known, if it doesn't benefit the developer then it can often be a wasted breath. Until it's mandatory I'm still going to pursue proper environmental methods in containing runoff. In a recent story on NBC, Chicago has made strong efforts toward developing rain gardens on roofs and become active within its streets and roadways to contain runoff.

    rain gardens and bio-swales seem in so many ways to be simple....their are a number of factors which drive the decision to pick certain BMPs, which include but not limited to:

    familiarity of the device by designers, developers, and owners
    construction cost
    maintenance cost
    ascetics of the bmps

    I know here in the western part of NC, the soil is primarily clay in natural which causes the construction cost of bio-retention facilities to almost 5 times the cost of those constructed in areas with sandy soil. Now the maintenance is the same, so its only a factor if the person responsible for the construction is in it for the long term or short term.

    here's a great paper on the economic impacts of BMPs in NC.

    I suggest trying to get funds to establish demo BMPs.... people are more accepting if they can see what you are talking about.

  6. #6
    Cyburbian craines's avatar
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    One area where they need to increase the study of is what plants have the abiltity to uptake toxins from the run-off and successfully process them. They are definitely species in from wet land habitats that have great success with this. Also certain grass species have work well in roadway swale applications.

  7. #7
    Cyburbian michaelskis's avatar
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    One of the things that our community did is use a combination of ornamental and native plantings, and designed it to double as a park. With a few water basins and fountains, it has enhanced what could have been a visually negative element.
    Not my monkey, not my circus. - Old Polish Proverb

  8. #8
    Cyburbian
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    rain gardens

    I've worked with my engineer teams to design rain gardens in several projects we've done recently. The most recent Dept. of Ecology (WA state) stormwater manual actually adopts by reference a supplemental LID manual that sets the standard for RG's.

    For one project we managed to combine the RG with a required frontage landscape buffer. This site had soils that had inadequate infiltration, so we designed the RG to act as detention and water quality, then discharge to an existing downstream outlet.

    Another project was brought to us by a developer who's prior consultant had designed some insanely expensive underground detention vaults (~$1.5 mil). We redesigned and managed to address detention and water quality through a system of elaborately vegetated swales and small pockets of deeper, rounder RG's. And we only lost a couple lots in the redesign. The RG construction costs are estimated around $500K; we saved the client a little less than $1 mil in construction costs.

    One thing that scares developers away from RG's is that the design and permitting can cost much more up front when compared to designing conventional ponds and vaults, and there is no guarantee the jurisdiction will buy off on your design. Often the permitting process can be a deal killer if the lead permitting agency is unfamilliar with LID and RG's.

    Also, there are misconceptions about RG's that cause many people to deem them infeasible for so many sites. For example, you don't need infiltration capability to make a RG work (see my first example above). Maintenance also scares people, but when you compare maintenance for an RG with vaults (vactor trucks, stormfilter replcement...) and the problems with ponds (large, unsightly, often unsafe), a RG is not such a daunting alternative.

  9. #9
    Cyburbian boilerplater's avatar
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    There has been a great deal of study on plants that can process toxic substances for use in reclamation of polluted ground. Google "Phytoremediation" and see also
    http://www.aehs.com/journals/phytoremediation/
    Yes, the research has been more on contaminated sites, but when you're directing contaminated runoff into a swale, you're essentially creating a contaminated site.
    This company in NJ has done a lot of research un using plants to remove heavy metals and radiation: http://clu-in.org/products/site/ongo...g/phytotec.htm
    I recall reading that they had a lot of investment interest but had failed to turn a profit. This was a few years ago, so things may have changed by now.
    Adrift in a sea of beige

  10. #10
    Cyburbian Plan 9's avatar
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    Bioswales are only one half of the solution. The primary purpose of bioswales is to remove organic materials (feces primarily) from seeping into the ground water, and they do a good job of it. However, a bioswale by itself will create an area where heavy metals can concentrate and potentially leach into the soil and ground water. Heavy metals mostly come off of cars that get rained on or drive through puddles in parking lots. The solution is to have a collector for heavy metals before the water is passed into the bio swale. Of course, the collectors have to be regularly maintained and the materials collected are usually a hazardous waste

  11. #11
    Cyburbian Jeff's avatar
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    Oh my Lord. Tell this to the state of Delaware. I hate doing work in the state because of how difficult they make the bio swale design process.

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