User talk:Jenny Hill

	Formal Infobox
Common name:	Wordiness virus
Medical name:	(see notebox below)
Habitat:	here, 19-Dec-2008

Many of the dimensions in a bioretention system are relatively constrained by the performance requirements of the individual component. There is greatest flexibility in the ponding depth and the depth of the storage reservoir beneath the optional underdrain pipe. The order of operations in calculating these dimensions depends on whether an underdrain is desired.

Component	Void ratio	Recommended depth (with underdrain pipe)	Recommended depth (no underdrain pipe)
Ponding depth	1	300 mm	See below
Mulch	0.7 for wood based 0.4 for aggregates	75 ± 25 mm
Biofiler media	0.3 typical	300 mm to support turf grass and accept only roof runoff 600 mm to support flowering perennials and decorative grasses 1000 mm to support trees
Choker course	0.4 typical	100 mm
Embedding reservoir	0.4	Is equal to underdrain pipe diameter	Not applicable
Storage reservoir	0.4	See below	See below

Sizing with an underdrain pipe[edit]

Determine what the planting needs are and assign appropriate depth of media.
Determine what the pipe diameter needs to be and assign appropriate depth of reservoir.
Determine maximum possible storage reservoir depth (d_S):

$d_{S}=f'\times 38.4$

Where:

f' = Design infiltration rate in mm/hr, and
38.4 comes from multiplying desired drainage time of 96 hours by void ratio of 0.4

Sizing without an underdrain pipe[edit]

Determine what the planting needs are and assign appropriate depth of media.
Determine what the pipe diameter needs to be and assign appropriate depth of reservoir.
Determine maximum possible storage reservoir depth (d_S):

$d_{S}=f'\times 38.4$

Where:

f' = Design infiltration rate in mm/hr, and
38.4 comes from multiplying desired drainage time of 96 hours by void ratio of 0.4

Then

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