Talk:Bioretention Design Guide

LID Practice		CANADA						United States
Bioretention		CVC+TRCA (Factsheets-2010)	CVC-Construction Guide-2012	CVC-Retrofit Guide-2014	Toronto- 2016	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	Pennsylvania-City of Philadelphia green St. design manual-2014	Minnesota SW Manual-2017	Tennessee-LID Development-SWM 2016	Texas-LID Technical Guidance Manual-2013	Oregon SWM Manual-2014	Oregon State Univ. Fact Sheets-2011
Filter media depth (m)
	Depth	1-1.25			1-1.25	1-1.25	0.5-1.0									>= 2.5 ft.
Composition
	Topsoil							30-50%	20-30 %				8-20 %			Table 1 & 2 (below)
	sand	85-88 %	Fine sand=0-17%, Coarse to medium sand=71-92 %	85-88 %	85-88 %	85-88 %	50-85 %	50-70	40%	85-88 %	65% sand, 20% sand loam	85-88 %	70-88 %	85-88 %	50-80 %		70-85 % (sandy loam)	85-88 %	66%	60% (sandy loam)
	Fines(silt and clay)	8-12 %	8-12 %	8-12 %	7-12 %	8-12 %	10-15% (silt),3-10% (clay), both combined, max 20%	clay < 5%		8-12 %		8-12 %		0-12 % silt, 0-2 % clay	Silt 40% , Clay 10%		10-20% (silt), max. 10% (clay)	8-12 %
	gravel														15%
	Organic matter	3-5 %	3-5 %	3-5 %	3-5 %	3-5 %	5-10%	5%	30-40 %	1-5 %	2-5 %	3-15 %	3-5 %	3-5 %	2-10 %		5-10 %	2-5 %	33%	40%
	P-index value	10-30 ppm			12-30 ppm	10-30 ppm				10-30								< 15
	Soluble salts				< 2.0 mmhos/cm
	Cationic exchange capacity	> 10 meq/100 g	10 meq/100 g	> 10 meq/100 g	> 10 meq/100 g	> 10 meq/100 g	> 5 meq/100 g			> 10	> 5		> 10				> 10			> 5
	pH	5.5-7.5	5.5-7.5	5.5-7.5	5.5-7.5	5.5-7.5	5.5-7.5				6-8				6-7	6-8.5 (WQ blend)		6-8		5.5-7.5
	Phosphorus						10-30 ppm									Table 1 & 2 (below)
	Infiltration rate	> 25 mm/hr	> 25 mm/hr	> 25 mm/hr	> 25 mm/hr
	Surface resistance				<= 110 PSI
	Sub-surface resistance				<= 260 PSI
	Saturated hydraulic conductivity , mm/hr						25 min.
	P-Content									10-30	< 15 ppm		7-23 mg/kg
	Compost (optional)						15-25%				15%
Gravel storage
	Void space ratio	0.4				0.4
	Depth	min. 300 mm			min. 300 mm	min. 300 mm
	Diameter(clear stone)	50 mm			50 mm	50 mm
Pea gravel choking layer	depth (mm)	100				100	100
	diameter (mm)	3-10				3-10
Mulch
	Depth	75 mm	<=75 mm		75 mm	75 mm	70-80
Overflow
	Overflow invert above the filter bed surface	150-250			<= 250 mm
Monitoring well
	Vertical perforated pipe diameter	100-150 mm	100-150 mm		100-150 mm	100-150 mm
Underdrain
	Required when infiltration rate	< 15 mm/hr			< 15 mm/hr		< 13 mm/hr
	Diameter	min. 100 mm(200 mm recommended)	min. 100 mm, 200 mm is recommended		min. 200 mm	min. 100 mm(200 mm recommended)	200 mm									4 inches
	Depth above the gravel storage layer	100 mm			100 mm
	Available head beween the inflow point and the downstream stream drain invert	1-1.5 m				1-1.5 m							Typical CDA 0.1-2.5 acres of 100% IP(<0.5 no underdrain), alternative to checking layer is needle punched non-woven geotextile
Contributing drainage area
	Typical	100 m2 to 0.5 hectare				100 m2 to 0.5 hectare						0.5-2 acres preferred, max 5 acres, BR min. size 200 ft2				5 acres
	Maximum recommended	0.8 hectare				0.8 hectare
Setback from building Foundation(m)		4			4	4	3 (clay), 5 (heavy clay)									see table 3 below
(Impervious drainage/treatment facility) area		5:1 to 15:1			5:1 to 15:1	5:1 to 15:1		< 5:1 loading ratio (DA to IA, DA 100% IP)	SA of BR 3 to 6% of CDA			sized at 5-8 % of IPCDA	BR SA 3-6% of CDA			CDA < 5 acres	CDA < 2.5 acres	CDA < 5 acres		BR SA: 6-15 % of IP area
Contributing Slope (%)		1-5				1-5										>1 % and < 33%
Slope of the surface, %																<= 1%
Water table depth		min. 1.0 m				min. 1.0 m	> 1.8									3 ft.
Outlet			min. 100 mm above the bottom of the facility													Difference in elevation between inflow and outflow =4-6 ft (when underdrain is used)
Maximum ponding depth above the filter bed surface		150-250 mm			250 mm	150-250 mm	350 mm									18 inch
Facilties receiving road runoff are not located within time of travel		2				2
wellhead protection areas, year
Drainage time of ponded water after the end of storm event , hr						24 (48 recommd.)	< 48 (2 yr. design)									Max. 48 hr.
Inlet design for non-point source-grass filter buffer, m							0.5-3.0
Contributing impervious area							< 4.0 ha.	`											< 15000 ft2
Facility flow velocity							< 0.3 m/s-planted area									<= 1 ft/sec, tree-shurb-mulch cell
							< 0.9 m/s- mulched zone									<= 3 ft/sec , grassed cell
Discharge velocity (outlet point)																< 4 ft/sec
Side slope (H:V)							4:1 preferred(max 2:1)									3:1 (H:V)
Surface geometery (length/width)							2:1
Infiltration trench (optional)
	Depth, m						0.5-1.0
	Width, m						1.0-6.0
	Bottom slope, %						0
C/N Ratio															12:1-25:1

Table 1:	Bioretention media composition
		Sand	Soil Fines	Organic	P-Index, milligram/kg	Gravel
Water Quality Blend		60-70 %	< 5% clay	15-25 %	10-30
Enhanced filtration blend		70-85 %		15-30 %	10-30
North Carolina WQB		85-88 %	8-12 %	3-5 %	10-30
Mix D by dry Weight		60-75 %	25-40 %	2-5 %		< 12 %
Mix E		60-80 %	20-40 % MnDot 3890 grade 2 compost	30%
Mix F by weight		75% loamy sand	25 % MnDot grade 2 compost

Table 2: Minimum bioretention soil media depths recommended to target specific stormwater pollutants
Pollutant	Depth of Treatment with upturned elbow or elevated underdrain	Depth of Treatment without underdrain or with underdrain at bottom	Minimum depth
Total suspended solids (TSS)	Top 2 to 3 inches of bioretention soil media	Top 2 to 3 inches of bioretention soil media	Not applicable for TSS because minimum depth needed for plant survival and growth is greater than minimum depth needed for TSS reduction
Metals	Top 8 inches of bioretention soil media	Top 8 inches of bioretention soil media	Not applicable for metals because minimum depth needed for plant survival and growth is greater than minimum depth needed for metals reduction
Hydrocarbons	3 to 4 inch Mulch layer, top 1 inch of bioretention soil media	3 to 4 inches Mulch layer, top 1 inch of bioretention soil media	Not applicable for hydrocarbons because minimum depth needed for plant survival and growth is greater than minimum depth needed for hydrocarbons reduction
Nitrogen	From top to bottom of bioretention soil media; Internal Water Storage Zone (IWS) improves exfiltration, thereby reducing pollutant load to the receiving stream, and also improves nitrogen removal because the longer retention time allows denitrification to occur underanoxic conditions.	From top to bottom of bioretention soil media	Retention time is important, so deeper media is preferred (3 foot minimum)
Particulate phosphorus	Top 2 to 3 inches of bioretention soil media.	Top 2 to 3 inches of bioretention soil media.	Not applicable for particulate phosphorus because minimum depth needed for plant survival and growth is greater than minimum depth needed for particulate phosphorus reduction
Dissolved phosphorus	From top of media to top of submerged zone. Saturated conditions cause P to not be effectively stored in submerged zone.	From top to bottom of bioretention soil media	Minimum 2 feet, but 3 feet recommended as a conservative value; if IWS is included, keep top of submerged zone at least 1.5 to 2 feet from surface of media
Pathogens	From top of soil to top of submerged zone.	From top to bottom of bioretention soil media	Minimum 2 feet; if IWS is included, keep top of submerged zone at least 2 feet from surface of media
Temperature	From top to bottom of bioretention soil media; Internal Water Storage Zone (IWS) improves exfiltration, thereby reducing volume of warm runoff discharged to the receiving stream, and also improves thermal pollution abatement because the longer retention time allows runoff to cool more before discharge.	From top to bottom of bioretention soil media	Minimum 3 feet, with 4 feet preferred

Table 3: Recommended minimum setback requirements
Setback from	Minimum Distance (m)
Property Line	10
Building Foundation*	10
Private Well	50
Septic System Tank/Leach Field	35
* Minimum with slopes directed away from the building

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

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.

The engineered soil component of bioretention cell or dry swale designs, typically with a high rate of infiltration and designed to retain contaminants through filtration and adsorption to particles.

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 particles with a diameter less than 0.050 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).

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).

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.

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.

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

a top dressing over vegetation beds that provides suppresses weeds and helps retain soil moisture in bioretention cells, stormwater planters and dry swales.

A perforated pipe used to assist the draining of soils.

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

A perforated pipe used to assist the draining of soils.

Filter fabric that is installed to separate dissimilar soils and provide runoff filtration and contaminant removal benefits while maintaining a suitable rate of flow; may be used to prevent fine-textured soil from entering a coarse granular bed, or to prevent coarse granular from being compressed into underlying finer-textured soils.

The total surface area upstream of a point on a stream that drains toward that point. Not to be confused with watershed. The drainage area may include one or more watersheds.

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

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

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 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 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 period between the maximum water level and the minimum level (dry weather or antecedent level).

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

a top dressing over vegetation beds that provides suppresses weeds and helps retain soil moisture in bioretention cells, stormwater planters and dry swales.

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.

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

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.

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

(1) Something that pollutes, especially a waste material that contaminate air, soil, or water. (2) Any solute or cause of change in physical, chemical or biological properties that render water unfit for a given use.

Total suspended solids

The downward movement of water through the soil, the downward flow of runoff from the bottom of an infiltration BMP into the soil.

Loss of water from a drainage system as a result of percolation or absorption into the surrounding medium (e.g., the infiltration of water into the native soil through a perforated pipe wall as it is conveyed).

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