Site considerations

LID Stormwater Management Practice	Depth to High Water or Bedrock (m)	Typical Ratio of Impervious Drainage Area to Treatment Facility Area	Native Soil Infiltration Rate (mm/hr)	Head (m)	Space %	Slope %	Applicable in Pollution Hotspots	Set Backs	Water Table	Wellhead Protection Area
Rain Barrel	Not applicable	[5 to 50 m2]	Not applicable	1	0	NA	Yes	None	None	None
Cistern	Not applicable	1:1	Not applicable	0	0	0	Yes	None	None	None
Roof Downspout Disconnection	Not applicable	[5 to 100 m2]	Amend if < 15 mm/hr	0.5	5 to 20	1 to 5	Yes	Building Foundation	None	None
Soakaway, Infiltration Trench or Chamber	1	5:1 to 20:1	Not a constraint	1 to 2	0 to 1	<15 %	No	4m- Building Foundation Underground Utilities, Trees, Drinking Water Wellhead Protection Areas	1 m	2 yr
Bioretention	1	5:1 to 15:1	Underdrain required if < 15 mm/hr	1 to 2	5 to 10	0 to 2	No	4m- Building Foundation Underground Utilities, Trees, Drinking Water Wellhead Protection Areas	1 m	2 yr
Biofilter (Filtration only Bioretention Design)	Not applicable	5:1	Not applicable	1 to 2	2 to 5	0 to 2	Yes	Building Foundation, Trees	None	None
Vegetated Filter Strip	1	5:1	Amend if < 15 mm/hr	0 to 1	15 to 20	1 to 5	No	None	None	None
Permeable Pavement	1	1:1 to 1.2:1	Underdrain Required if < 15 mm/hr	0.5 to 1	0	1 to 5	No	4m-Underground Utilities Drinking Water Wellhead Protection Areas	1 m	2 Yr
Enhanced Grass Swale	1	5:1 to 10:1	Not applicable	1 to 3	5 to 15	0.5 to 6	No	4m- Building Foundation Underground Utilities	1 m	None
Dry Swale (Bioswale)	1	5:1 to 15:1	Underdrain Required if < 15 mm/hr	1 to 3	5 to 10	0.5 to 6	No	4m (3m if impermeable liner is used)Building foundation, Underground utilities, drinking water wellhead protection areas	1 m	2 Yr
Perforated Pipe System	1	5:1 to 10:1	Not a constraint	1 to 3	0	< 15%	No	4m- Building Foundation Underground Utilities, Trees, Drinking Water Wellhead Protection Areas	1 m	2 Yr

Low Impact Development. A stormwater management strategy that seeks to mitigate the impacts of increased urban runoff and stormwater pollution by managing it as close to its source as possible. It comprises a set of site design approaches and small scale stormwater management practices that promote the use of natural systems for infiltration and evapotranspiration, and rainwater harvesting.

A hard surface area (e.g., road, parking area or rooftop) that prevents or retards the infiltration of water into the soil.

Tank used to store rainwater (typically roof runoff) for later use.

An underground water storage reservoir into which stormwater is directed and allowed to percolate into the underlying native subsoil.

An excavated area lined with geotextile filter cloth and filled with clean granular stone or other void forming material, that receives runoff and allow it to infiltrate into the native soil; can also be referred to as infiltration galleries, French drains, dry wells or soakaway pits.

A shallow excavated surface depression containing prepared filter media, mulch, and planted with selected vegetation.

A perforated pipe used to assist the draining of soils.

A bioretention BMP featuring an impermeable liner and underdrain that prevents infiltration of runoff into the underlying native soil; provides sedimentation and filtration of urban runoff as it passes through the mulch layer, engineered filter media and vegetation root zone.

A bioretention cell that features an impermeable liner that collects and treats stormwater through sedimentation and filtration only (i.e., no infiltration).

The technique of removing pollutants from runoff as it infiltrates through the soil.

A shallow constructed channel, often grass-lined, which is used as an alternative to curb and channel, or as a pretreatment to other measures. Swales are generally characterized by a broad top width to depth ratio and gentle grades.

Linear bioretention cell designed to convey, treat and attenuate stormwater runoff. The engineered filter media soil mixture and vegetation slows the runoff water to allow sedimentation, filtration through the root zone, evapotranspiration, and infiltration into the underlying native soil.

The upper surface of the zone of saturation, except where the surface is formed by an impermeable body.

Subsurface water level which is defined by the level below which all the spaces in the soil are filled with water; The entire region below the water table is called the saturated zone.

The rate at which stormwater percolates into the subsoil measured in inches per hour.

A parameter that describes the capability of a medium to transmit water.

The portion of water precipitated onto a catchment area, which then flows as surface discharge from the catchment area past a specified point.

Water from rain, snow melt, or irrigation that flows over the land surface.