Atlan Bio

Why is Bioretention Layered?

Bioretention uses a combination of media layers to achieve stormwater outcomes and to mimic natural compositions – bridging the gap between our urban landscapes and nature. SPELBio is our approach to providing high-quality biomedia. 

The composition of these layered systems is resistant to erosion, mitigates flooding, filters stormwater, and provides stability during stormwater events. 

The top layers of bioretention systems are composed of mulch, vegetation and biofiltration media. The vegetation layer contains treatment-specific plants, which are supported by the mulch layer and the underlying biofiltration media. These layers typically contain compost, soil and other components and act as a growth medium. 

The biofiltration layer is also important for hydrological function, filtration, and stormwater conveyance.  

Stormwater is treated by all these different elements – via chemical and biological interaction with soil microbes and plant roots, and the physical interactions and media-based filtration of the underlying layers. 

The lower layers are composed of the transition layer and drainage layer, which help to ensure water can flow into surrounding soils or nearby drainage. You can find specific information on each of these different layers in our blog here.  

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