Bioretention cells are bowl like gardens that capture and temporarily impound runoff. Captured runoff and pollutants are filtered out as water percolates downward. Bioretention cells have an engineered subgrade that features a 1 foot layer of rock with a perforated tile about 3.5 below the surface, which is typically covered by a specified soil mix that allows water to readily move down through the system.
Bioretention cells filter pollutants out of dirty runoff. Biocells capture sediment, heavy metals, hydrocarbons, floatable litter and other pollutants in stormwater runoff. Biocells filter, cool and slowly release dirty runoff that otherwise would go directly to receiving streams without any treatment. Biocells and their engineered subgrades are used where soils are altered, compacted, or have other characteristics that don't allow water to percolate down through the soil profile.