From past NCSU experience with the construction of bioretention areas, here are 10 helpful tips listed chronologically from the beginning/prior to construction to the end of construction.
Determine water table elevation with great care. High water tables turn bioretention into wetlands.
The permeability and phosphorus content of fill media should be determined prior to construction.
Avoid constructing bioretention near disturbed areas. Excessive sedimentation ruins bioretention. Be wary of out-parcel development.
Construction sequencing is critical and must be well-timed and executed.
Sediment traps and basins can be transformed to bioretention areas, provided they are adequately cleaned immediately prior to bioretention conversion.
If the bioretention cell treats a parking lot, the base gravel course needs to be placed prior to installation of a bioretention's underdrains, gravel layer, or fill media. Ideally, the initial asphalt layer is placed prior to post-excavation construction.
Include some pretreatment. Options include: (a) a gravel verge with sod surrounding the perimeter, (b) a grass swale, or (c) forebays.
Any exposed edge/side of a bioretention cell should be sodded as soon as possible after construction is complete.
Taller vegetation, like trees need to be staked during the first year they are in the bioretention bed. Shallow soil makes it difficult for trees to survive high wind events.
Immediately after construction it may be necessary to irrigate the sod perimeter and the vegetation in the bioretention cell. Protect your investment!
