Structural practices summary

LID Design Guide Detail

	Available Space	Site Topography	Available Head	Soils	Pollution Hot Spot Runoff	Setbacks from Buildings	Proximity to Underground Utilities	Set Backs	Drainage Area and Runoff Volume	Wellhead Protection	Water Table	Overhead Wires	Flow Path Length Across Impermeable Surface	Winter Operations	Vehicle Loading	Structural Requirements	Roof Slope
Roof Downspout Disconnection	Simple downspout disconnection requires a minimum flow path length across the pervious area (at least 5 metres) and suitable soil conditions. If the flow path length is less than 5 metres and soils are hydrologic soil group (HSG) C or D, roof downspouts should be directed to another LID practice such as a rainwater harvesting system, soakaway, swale, bioretention area or perforated pipe system.	Disconnected downspouts should discharge to a gradual slope that conveys runoff away from the building. The slope should be between 1% and 5%. Grading should discourage flow from reconnecting with adjacent impervious surfaces		If the infiltration rate of soils in the pervious area is less than 15 mm/hr, they should be tilled to a depth of 300 mm and amended with compost to achieve an organic content in the range of 8 to 15% by weight or 30 to 40% by volume.	Downspout disconnection can be used where land uses or activities at ground-level have the potential to generate highly contaminated runoff as long as the roof runoff is kept separate from runoff from groundlevel impervious surfaces
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.

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.

The total mass of a pollutant entering a waterbody over a defined time period.

The net amount of something (e.g. chemical, such as phosphorus), calculated as the product of concentration and volume in a given time. Some BMPs significantly reduce loading of pollutants to the environment by reducing volume more so than concentration.

The practice of intercepting, conveying and storing rainwater for future use. Captured rainwater is typically used for outdoor non-potable water uses such as irrigation, or in the building to flush toilets.

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 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.

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

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.

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

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

Decayed organic material used as a plant fertilizer. Compost helps to support healthy plant growth through the slow release of nutrients and the retention of moisture in 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.