Science or Fiction?

[Andrew Garulay, RLA]

I have not mischaracterized anything, but have been very mischaracterized by you. I like rain gardens and bioswales except when we have to put them in rediculous locations – in tree islands of 200 -400 SF. I do new construction as well as redevelopment and NONE of any drainage that I’ve worked on is piped or swaled off site, let alone into the ocean.

I do want to protect the earth. That is why I wish there was readily available quantifiable information on how much excess nutrients and other contaminants are present and removed in various situations. If a rain garden in a 200 SF tree island makes a significant difference, I want to put them in. If it is insignificant, I’d rather not build a trash catcher, Buick gobbler, and mosquito farm just to feel good about something that is causing more problems than it solves.

[Trace One]

but the purpose is not only sediment /pollution trapping, Andrew, but on-site water retention. In that case, a rain garden (which is a silly word for a simple concept) is ALWAYS better than paving, no?
And you DID say that the general feeling is if you don’t put rain gardens everywhere ‘we will all die.” I think this is mischaracterizing your ‘opposition.’
And I also think your problem is the ordinances, not the rain gardens..How freaking hard is it to put a ‘rain garden’ anywhere? give me a break..

[Trace One]

http://www.ence.umd.edu/~apdavis/Bio-research.htm

C’mon guys, you are not looking if you are not finding quantification of removal of pollutants by bio-swales..
http://www.raingardens.org/bioretention.php

That page has a link to the first page I posted the link to, which is Univ of Md. research, ALL of it involving quantification of removal of pollutants..
And like I said, removal of pollutants is NOT the only purpose..

[Trace One]

And also, Andrew, while you may not have worked on any projects that swale stormwater out to the ocean, my point was that almost all old systems go right out to the water, river, ocean, whatever. Retrofitting has been done, but man when it rains in San Diego, the stormwater, and frequently the sewage, for that matter, is dumped right out in the ocean, beaches are all posted as contaminated after rains, and the bay is filled with crap from the storm drains..

So andrew, while you may not have worked on any of these, my point is, that is the design for MOST existing systems..So in our work, on new projects, we have more responsibility to deal with everything under our power, and not to leave it for other developments…

[Roland Beinert]

Alec,
I’d recommend you look into constructed wetlands rather than swales or raingardens. These might be more along the lines of what you need for the splash pad. I found this article on BMP’s and bacteria removal, though: http://www.stormh2o.com/may-2008/bacterial-research-bmps.aspx
To summarize the article, rain gardens are somewhat effective at removing bacteria, but not to levels below primary contact for recreation levels.Turns out some types of swales are not that effective at removing bacteria at all and in some cases bacteria levels were increased (probably due to ducks, geese and pets using them as toilets).
Here’s a link to an article on constructed wetlands: http://www.extension.umn.edu/distribution/naturalresources/DD7671.html
I think some people are taking this discussion as an excuse to talk about whether bioswales and rain gardens should be used at all, which is a bit ridiculous, since Alec is talking about a specific situation. Do they collect trash? Maybe sometimes, but where would that trash go otherwise? Down a drain or into a lake or stream? I’d say there’s much more incentive to clean the trash up if it’s concentrated in a swale. The mosquito issue has been talked about over and over. Just keep the water from sitting there for more than 72 hours. Will people drive their cars into a swale? Maybe, but that’s why you post a sign or put in some sort of barrier.

[Trace One]

Roland, I don’t know if we are taking this to extreme – Alec is saying it is impossible to verify the science behing filtration, by stating that it might be fiction. This leaves the topic way broader than just his specific situation.

[Alec Johnson, PLA]

Thanks Roland. This is exactly the same conclusion I reached. We already have a constructed wetland at the end of this treatment chain that I am convinced will remove 65%-90% of the bio-nasties. The grey water hits 2 rain gardens and travels 1000 lf down a swale to the wetlands. I was hoping to find factual proof that the rain gardens and swale would treat the remaining percentage, but did not. None of the research (including the studies Trace cites) go that far.

[Alec Johnson, PLA]

Wow. I maintain that the title of my discussion accurately describes my conundrum. Furthermore, my description of aforementioned conundrum was specific in it’s wording. Thanks all.

[Andrew Garulay, RLA]

ALL drainage is absorbed on site on our projects. Only very few municipal systems have some old networks of pipes, but no one can add to those even if they wanted to. We use rain gardens, bioswales, catch basins into leach pits or other infiltration devices. It all replenishes the groundwater on site. Preferably, it is filtered through vegetation, but more often than not it is only leached in through the sand.

As a matter of fact, we just installed a couple of catch basins and galley system to pick off some municipal road runoff that was going into one of those old direct pipes that discharges next to a beach. It was our idea as a gesture to sweeten a water front project. That is one example of development being a mechanism to improveexisting situations. Granted, it is unusual for it to come directly from the developer’s team rather from a regulating agency, but neither happens without the development or massive spending by government (I prefer development paying for it).

Hopefully, everyone else understood that “we are all going to die” was an exaggerated description as was the comment that “all water will be pure”. I think most people know where you are coming from by now.

[Roland Beinert]

Sorry Trace. I guess I joined the discussion late, so I don’t have the full picture.

[Alec Johnson, PLA]

Word.

[Trace One]

wow! ALL the projects I work on ultimately drain to a city system, hopefully having been treated first – and that includes projects in Orange Virginia..

Sorry if I mistook humour for truth..

All right, all right, over-reacted..Alec you should write headlines, it definitely got my attention..to say the least..Apologize for over-reacting..Toilet flooding at home, cats are gone – many other excuses..sorry..!!

[Alec Johnson, PLA]

No need to apologize Trace. I enjoy a lively discussion. There are no easy answers to complex questions.

[Mike G]

Alec,
Most bacteria tested (fecal bacteria) are tested as an indicator of more dangerous organisms and the excess nutrients they consume. If there’s less nutrient then there should be less bacteria, visa versa.

[Christa]

The following attachments were given to me by a horticulture and toxicology professor at my university when I asked her about phytoremediation for a rain garden project.

The Phytoremediation paper by Elizabeth Pilon-Smits lists plant genus names within the discussion of each type of pollutant/remediation scenario. It also contains some really clear graphics of the phytoremediation process. The rain garden/bioretention paper is from NC State Extension. It is detailed, and includes some simple diagrams. The filter strip article is published by the University of California, and is oriented toward agricultural runoff, but it is well written (albeit perhaps a little technical) and applies to other situations as well.

I hope this helps! The Google search is a good idea, but you might have better luck avoiding the fiction if you stick to Google Scholar and your local university library. As for completed studies with accompanying data, I don’t personally have anything like this handy, but maybe you could backtrack the article references and find something. I know NC State is active in this area. Good luck! Post what you find!!
Christa

[Author]

Posts