Bioretention with no underdrain

[IGdawg]

Hi! I have a small project of building a park (mostly concrete surface with planting area on one side). The client wants to make the planting area into bioretention area. But the soil type is D and we do not have storm drain system nearby to connect. Is there anything I can do?

When I told him it may not be suitable for this project, the client asked me a good question and I did not have a good answer. He said: what's the difference if the planter area wasn't a bioretention area and just a normal landscaped area. Runoff still goes into the area and seep through the soil as much as it can then overflow. Would it be a problem because we don't have a underdrain?

Hmm, good point. Any input?

 

[beej67]

D soils are are a real drag, but it's hard to say without knowing more. Have you had a perk test done? You might be able to find someone who can do one for a few hundred bucks, and get some clarity with your design.

Where's the site? (state/city) How high is the water table?

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[civilman72]

Is a regulatory agency requiring the bioretention pond? If the client just wants to install it for his own piece of mind, then he can do what he wants.

The easiest way to remedy the lack of a drain is to install more (deeper and or wider) porous material, assuming your groundwater table is not too high.

 

[mherr78]

If you don't have any positive outfall, and the area will hold water for an extended period of time, you may be unintentionally creating a regulated wetland. How much new impervious cover are you providing? It would seem that you are increasing the rate of flow and volume of flow. You might want to consider creating a bioretention facility with enough void space to store the runoff for a certain design storm, like the 2-year or the 10-year so you do not have standing water for an extended period of time. Then hopefully, you wouldn't have back-to-back storms and the facility would have time to drain.