Talk:Green Roofs Design Guide

LID Practice		CANADA			United States
Green Roof		CVC+TRCA (Factsheets-2010)	LID-SWM Guide 2010	LID-Design Guide Edmonton- 2014	New York State SWM Design Manual-2015	Massachusets SW BMP-2013	District of Columbia-SWM Guidebook-2010	San Diego LID Handbook-2014	Alabama LID Handbook-2013	W. Virginia-SWM design guidance manual-2012	Rhode Island-SW design & Installation Standards Manual-2012	Minnesota SW Manual-2016	Tennessee-LID Development-SWM 2016	Texas-LID Technical Guidance Manual-2013	Oregon SWM Manual-2014	Oregon State Univ. Fact Sheets-2011
Slope (%)		<= 10	<= 10	< 5 (requires sloped underdrain), 5-20 (gravity drainage), > 20 lath grid is required				See Table 2 for Media specs (Below)
Green roof assembly Weight(kg/m2)		80		290-967.7 (Intensive), 129.1-169.4 (Extensive)
Growing medium depth (cm)		4-15	4-15
Intensive		> 15	> 15	20-60
Extensive		<= 15	<= 15	10-15
Fertilizer applications (nitrogen/m2)		< = 5.0 g
Porosity of the drainage Layer (%)		> = 25%	> = 25%
Ratio of impervious area to treatment facility area, %			1:1				CDA:GR size +25%				DA not limit, generally no runoff from surrounding area
Plant density				Seeds >= 325/m2, Cuttings>= 12 kg/100m2, Plugs>= 11/m2
Filter Media
Organic					25%	< 5%	<20%		< 15%	<20%	< 15%	See Table 1 for media parameter ranges	< 15%	< 20%	25%	20%
Light Weight in-organic					75%	95-100 %	80-90%	100%	> 85%	80-90%	85-100 %		80-90 %	80-90 %	50%
CEC								> 10			> 10			> 10
pH								6.5-8				6.5-7.8		6.5-8
Sand											S: 95%; D:85-95%
Silt											S: <5%; D: 5-15%
Clay											0%
P-Content												E: 2-10; I:2-15
Topsoil															25%
Porous Material																70%
Digested fiber																10%

Table 1: Recommended green roof growing medium parameter ranges
Parameter	Extensive green roofs	Intensive green roofs
pH	6.5 to 7.8	6.5 to 7.8
Nitrate-N (mg/L)	1 to 4	2 to 32
Ammonium-N (mg/L)	0.1 to 0.8	0.1 to 0.8
Nitrogen (total) (mg/L)	2 to 8	2 to 32
Phosphorus (total) (mg/L)	2 to 10	2 to 15
Potassium (mg/L)	8 to 32	8 to 64
Calcium (mg/L)	100 to 300	100 to 300
Magnesium	10 to 80	10 to 80
Iron (mg/L)	8 to 32	8 to 32
Manganese	1 to 8	1 to 8
Boron (mg/L)	0.04 to 0.6	0.04 to 0.6
Sodium (mg/L)	<20	<20
Zinc (mg/L)	1 to 10	1 to 10
Soluble salts (mmhos/cm)	0.4 to 1.2	0.4 to 1.2
Sodium Absorption Ratio (SAR)	<2	<2

Table 2:Example green roof media specifications
Parameter	Specification
Noncapillary pore space at field capacity	155 (vol.)
Moisture content at field capacity	12% (vol.)
Maximum media water retention	30% (vol)
Alkalinity, CaCo3 equivalents	2.50%
Total organic matter by wet combustion	3-15% (dry wt.)
pH	6.5-8.0
Soluble Salts	6 mmhos/cm
Cation exchange capacity	10 meq/100g
Saturated hydraulic conductivity for single media assemblles	0.05 in/min
Clay fraction (2 micron)	0
Pct. Passing US#200 sieve (i.e., silt fraction)	5%
Pct. Passing US#60 sieve	10%
Pct. Passing US#18 sieve	5%-50%
Pct. Passing 1/8 inch sieve	20%-70%
Pct. Passing 3/8 inch sieve	75%-100%

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.

Credit Valley Conservation

Toronto and Region Conservation Authority

Stormwater Management

Best management practice. State of the art methods or techniques used to manage the quantity and improve the quality of wet weather flow. BMPs include: source, conveyance and end-of-pipe controls.

A perforated pipe used to assist the draining of soils.

Natural or artificial means of intercepting and removing surface or subsurface water (usually by gravity).

A thin layer of vegetation and growing medium installed on top of a conventional flat or sloped roof, also referred to as living roofs or rooftop gardens.

The porosity (n) of a mixture is the ratio of the volume of void-space to the total or bulk volume of the mixture. It is closely related to the concept of void ratio (e) where void ratio is the ratio of the volume of void-space to the volume of solids. n = Volume of voids/Total volume of mixture = e/(1+e)

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

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.

Mineral particles which are smaller than 2 mm, and which are free of appreciable quantities of clay and silt. Coarse sand usually designates sand grains with particle size between 0.2 and 0.02 mm.

Soil or media particles smaller than sand and larger than clay (3 to 60 m)

1. A mineral soil separate consisting of particles less than 0.002 millimeter in equivalent diameter. 2. A soil texture class. 3. (Engineering) A fine-grained soil (more than 50 percent passing the No. 200 Sieve) that has a high plasticity index in relation to the liquid limit. (Unified Soil Classification System).

A thin layer of vegetation and growing medium installed on top of a conventional flat or sloped roof, also referred to as living roofs or rooftop gardens.

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

Soil or media particles smaller than sand and larger than clay (3 to 60 m)