Low Impact Development Tool Kit
Determining the Size of a Infiltration or Filtration LID System
Low Impact Filtration Devices such as Bioretention Cells, Landscape Planters Etc.
Minimum recommended size for the infiltration device is 5% of the sites drainage area.
Device Information (overwrite data in yellow cells, other cells will be automatically calculated)
Size of the impervious area draining to the infiltration device
acres
=
sq.ft.
Actual total area of the infiltration device
(Should be at least
sq.ft.
)
sq.ft.
=
Average depth of the infiltration device (from top of engineered soil to outlet)
inches
=
ft.
Infiltration porosity (volume fraction of soil pores)*
Depth of engineered soil within the infiltration device.***
inches
=
ft.
Infiltration device's total volume
cubic ft.
*Typical value ranges from 25-60% (.25-.60). Use 0 if you only want to count above-ground storage.
To learn how to calculate porosity
click here
**Brady, N. C. and R. R. Weil (2002). The Nature and Properties of Soils. Upper Saddle River, Prentice Hall.
*** Recommended minimum depth of the engineered soil within the infiltration device is 24 inches.
Modified from LID Filtration Device Spreadsheet developed by the Center for Low Impact Development - and used here with their permission
From: Multi-Functional Landscaping: Putting Your Parking Lot Design Requirements to Work for Water Quality, M. Quigley and T. Lawrence
