#LID Defaults from the EPA SWC

The following defaults are from the EPA Stormwater Calculator

https://www.epa.gov/water-research/national-stormwater-calculator

A few of these parameters such as the capture ratio are not parameters in InfoSWMM Sustain

There are some additional points to keep in mind when applying LID controls to a site:

1.      The area devoted to Disconnection, Rain Gardens, and Infiltration Basins is assumed to come from the site’s collective amount of pervious land cover while the area occupied by Green Roofs, Street Planters and Porous Pavement comes from the site’s store of impervious area.

2.      Underdrains (slotted pipes placed in the gravel beds of Street Planter and Porous Pavement areas to prevent the unit from flooding) are not provided for. However since underdrains are typically oversized and placed at the top of the unit’s gravel bed, the effect on the amount of excess runoff flow bypassed by the unit is the same whether it flows out of the underdrain or simply runs off of a flooded surface.

3.      The amount of void space in the soil, gravel, and pavement used in the LID controls are listed in Table 4 below. They typically have a narrow range of acceptable values and results are not terribly sensitive to variations within this range.

Table 3. Editable LID parameters.

LID Type	Parameter	Default Value
Disconnection	Capture Ratio	100 %
Rain Harvesting	Cistern Size	100 gal
	Cistern Emptying Rate	50 gal/day
	Number of Cisterns	4 per 1,000 sq ft
Rain Gardens	Capture Ratio	5 %
	Ponding Depth	6 inches
	Soil Media Thickness	12 inches
	Soil Media Conductivity	10 inches/hour
Green Roofs	Soil Media Thickness	4 inches
	Soil Media Conductivity	10 inches/hour
Street Planters	Capture Ratio	6 %
	Ponding Depth	6 inches
	Soil Media Thickness	18 inches
	Soil Media Conductivity	10 inches/hour
	Gravel Bed Thickness	12 inches
Infiltration Basins	Capture Ratio	5 %
	Basin Depth	6 inches
Porous Pavement	Capture Ratio	100 %
	Pavement Thickness	4 inches
	Gravel Bed Thickness	18 inches

Table 4. Void space values of LID media.

Property	LID Controls	Default Value
Soil Media Porosity	Rain Gardens, Green Roofs and Street Planters	45 %
Gravel Bed Void Ratio	Street Planters and Porous Pavement	75 %
Pavement Void Ratio	Porous Pavement	12 %