Conservation Strategies for Growing Communities - Natural ...

Bioretention Cells . . . s h a l l o w, landscaped
d e p ressions that can handle large volumes of water f rom extensive
impervious surfaces found in commercial, institutional, industrial or
residential settings. Bioretention cells generally have an engineere d
substratum, due to altered and compacted soil conditions.
Design Techniques C h a l l e n g e s / L i m i t a t i o n s
• The subgrade of a bioretention • There is potential for fine particles
to accumulate in the surface
cell will usually include a tile
drain bedded in gravel and a soil layer of bioretention cells, which
matrix that is amended with sand could impede the percolation of
and compost to ensure at least 40 water through the soil profile.
percent pore space is maintained. • Maintain a mowed turf border
• Bioretention cell size can be up around the perimeter of the cell
to 30 percent of the square to trap fine particles and prevent
footage of the impervious surface
draining to the cell, but usu-
this potential problem.
ally will be less than ten percent.
The depth of the amended subgrade
affects the surface area of
the bioretention cell.
• Native trees and shrubs can be
planted to provide shading for
parking surfaces.
• Bioretention cells should be
strategically located to capture
roof runoff or segment impervious
surfaces to intercept runoff
before the volume becomes too
large.
A turfed island was converted into a bioreten -
• The underlying tile drain should
tion cell at this site. Curb cuts allow runoff to
be below frost lines to keep the enter the bio-cell for pollutant removal. Large
soil matrix drained.
runoff events can still enter storm sewers.
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