Changes

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!

!

!Blend A: Drainage priority

!Blend A: Drainage rate priority

!Blend B: Water quality priority

!Blend B: Water quality treatment priority

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|-

!Application

!Application

|Higher I/P ratio

|Impervious area to pervious area (I:P) ratio greater than 20:1

|

|

{{Plainlist|1=

{{Plainlist|1=

*More diverse [[Plant lists|planting]],

*More diverse [[Plant lists|planting]] options,

*Improved [[heavy metals|metals]] and [[phosphorus]] retention.}}  

*Improved [[heavy metals|metals]] and [[phosphorus]] retention.}}  

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|-

3 parts [[sand]]<br>  

3 parts [[sand]]<br>  

2 parts [[topsoil]]<br>  

2 parts [[topsoil]]<br>  

1 part sand [[Bioretention: Filter media#Organic components|organic soil components]] and [[Bioretention: Filter media#Additives|additives]]

1 part [[Bioretention: Filter media#Organic components|organic soil components]] and [[Bioretention: Filter media#Additives|additives]]

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|-

!

!Porosity

|This mixture may be assumed to have available water storage of [[Bioretention media storage|'''0.4''' unless demonstrated otherwise]]

|This mixture may be assumed to have a porosity of [[Bioretention media storage|'''0.4''']] unless demonstrated otherwise

|This mixture may be assumed to have available water storage of '''0.35''' unless demonstrated otherwise

|This mixture may be assumed to have a porosity of [[Bioretention media storage|'''0.35''']] unless demonstrated otherwise

|}

|}

Filter media should be obtained premixed from a vendor and meet all municipal, provincial and federal environmental standards. Mixing of sand, topsoil and compost should be done in a manner that preserves topsoil peds.

Filter media should be obtained premixed from a vendor and meet all municipal, provincial and federal environmental standards. Topsoil used to produce the mix should be passed through a 5 centimetre (2 inch) screen to remove large rocks, roots and other debris, while retaining soil peds. Samples of the filter media should be dried, ground and tested by a certified soil testing laboratory to ensure they meet the following specifications:

The mixture should be free of stones, stumps, roots, or other debris larger than 50 mm diameter. Samples of the filter media should be dried, ground and tested to ensure they meet the following specifications:

{|class="wikitable"

{|class="wikitable"

!Characteristic

!Characteristic

!Criterion

!Criterion

!Recommended method

!Recommended test method

|-

|-

![[Texture]]

![[Grain size analysis| Particle-size distribution (PSD)]]

|< 25% silt- and clay-sized particles combined; <br> < 10% clay-sized particles||Hydrometer

|< 25% silt- and clay-sized particles (smaller than 0.05 mm) combined; <br> 3 to 12% clay-sized particles (0.002 mm or smaller)||ASTM D7928, Standard Test Method for Particle-Size Distribution (Gradation) of Fine-Grained Soils Using the Sedimentation (Hydrometer) Analysis.

|-

|-

![[Organic matter]] (OM)

![[Organic matter| Organic matter (OM)]]

|5 to 10% by dry weight||ASTM F1647, Standard test methods for organic matter content of athletic field rootzone mixes.

|3 to 10% by dry weight||ASTM F1647, Standard Test Methods for Organic Matter Content of Athletic Field Rootzone Mixes.

|-

|-

![[Phosphorus]]

![[Phosphorus| Phosphorus, plant-available or extractable]]

|12 to 40 ppm||As measured by the 'Olsen' method for alkaline and calcareous soils (common in Ontario). Alternatives include 'Mehlich I or III', or 'Bray', better suited to acidic to slightly alkaline and non-calcareous soils. Results from these are not directly translatable.<ref>Sawyer JE, Mallarino AP. Differentiating and Understanding the Mehlich 3, Bray, and Olsen Soil Phosphorus Tests 1. http://www.agronext.iastate.edu/soilfertility/info/mnconf11_22_99.pdf. Accessed August 1, 2017.</ref>

|12 to 40 ppm||As measured by the 'Olsen' method for alkaline and calcareous soils (common in Ontario). Alternatives include 'Mehlich I or III', or 'Bray', which is better suited to acidic to slightly alkaline and non-calcareous soils. NB: Results from different test methods are not directly comparable.<ref>Sawyer JE, Mallarino AP. Differentiating and Understanding the Mehlich 3, Bray, and Olsen Soil Phosphorus Tests 1. http://www.agronext.iastate.edu/soilfertility/info/mnconf11_22_99.pdf. Accessed August 1, 2017.</ref>

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|-

![[Cationic exchange capacity(CEC)]]

![[Cationic exchange capacity(CEC)| Cationic exchange capacity (CEC)]]

|> 10 meq/100 g||ASTM D7503, Standard test methods for measuring the exchange complex and cation exchange capacity of inorganic fine grained soils.  

|> 10 meq/100 g||ASTM D7503, Standard Test Methods for Measuring the Exchange Complex and Cation Exchange Capacity of Inorganic Fine-Grained Soils.  

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|-

![[Hydraulic conductivity]]

!Hydraulic conductivity, saturated (K_f)

|> 25 mm/h <br> < 250 mm/h||Falling head or constant head KSAT

|> 75 mm/h; Blend A <br> > 25 mm/h; Blend B <br> < 300 mm/h; Blend A and B||ASTM D2434, Standard Test Method for Permeability of Granular Soils (Constant Head), when the sample is compacted to 85% of its maximum dry density in accordance with ASTM D698, Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Standard Effort.

|}

|}

Note that grain size distribution does not form part of the recommended acceptance criteria. Whilst this information may be useful in designing blends, the disconnect between hydraulic conductivity and the uniformity of gradation makes it far less important then measuring the hydraulic conductivity directly<ref>CRC for Water Sensitive Cities. (2015). Adoption Guidelines for Stormwater Biofiltration Systems: Appendix C - Guidelines for filter media in stormwater biofiltration systems.</ref>  

Note that you may choose not to use particle-size distribution as a criterion for acceptance of a filter media blend, but saturated hydraulic conductivity should be one. While information on particle-size distribution and soil texture are useful in selecting plants, the disconnect between hydraulic conductivity and uniformity of gradation makes it far less important than measuring the saturated hydraulic conductivity directly<ref>CRC for Water Sensitive Cities. (2015). Adoption Guidelines for Stormwater Biofiltration Systems: Appendix C - Guidelines for filter media in stormwater biofiltration systems.</ref>  

==Sand==

==Sand==

==Topsoil==

==Topsoil==

{{:Topsoil}}

{{:Topsoil}}

==Organic components==

==Organic component==

This is the first big opportunity to manage phosphorus export from a [[bioretention]] or [[stormwater planter]] system. Whilst compost is the most common ingredient, designers working in sensitive watersheds are encouraged to explore the alternatives listed below. Some of these materials may be combined 50:50 with compost to balance the nutrients required by the [[plants]] and the potential for leaching of excess nutrient.   

This is the first big opportunity to manage phosphorus export from a [[bioretention]] or [[stormwater planter]] system. While compost is the most common choice, designers working in nutrient-sensitive receiving waters are encouraged to explore the alternatives listed below. Some of these materials may be combined 50:50 with compost to balance providing the nutrients required by the [[plants]] with limiting the potential for leaching of excess nutrients.   

   

   

===Compost===

===Compost===

Compost is the most widely used organic component. It's use in bioretention facilities is well established and documented.  Low-phosphorus composts should always be sought for use in low impact development facilities, including bioretention. These are typically created from feedstocks including yard, leaf, and wood waste, and must exclude manures, biosolids, and food scraps.<ref>Hurley S, Shrestha P, Cording A. Nutrient Leaching from Compost: Implications for Bioretention and Other Green Stormwater Infrastructure. J Sustain Water Built Environ. 2017;3(3):4017006. doi:10.1061/JSWBAY.0000821.</ref><br>

Compost is the most widely used organic component. It's use in bioretention facilities is well established and documented.  Low-phosphorus composts should always be sought for use in low impact development facilities, including bioretention. These are typically created from feedstocks including yard, leaf, and wood waste, and excluding manures, biosolids, and food scraps.<ref>Hurley S, Shrestha P, Cording A. Nutrient Leaching from Compost: Implications for Bioretention and Other Green Stormwater Infrastructure. J Sustain Water Built Environ. 2017;3(3):4017006. doi:10.1061/JSWBAY.0000821.</ref><br>

'''[[Compost|Compost Specifications]]'''

'''[[Compost|Compost Specifications]]'''

Even low-phosphorus composts are known to export phosphorus over many years. The use of compost is not recommended in watersheds for which phosphorus pollution is a concern. There are alternatives which have undergone field study, each of which has a number of benefits and potential concerns:

Even low-phosphorus composts are known to export phosphorus over many years. The use of compost is not recommended in nutrient-sensitive watersheds where phosphorus pollution is a concern. There are a number of alternative sources of soil organic matter which have undergone field studies which have benefits and potential concerns:

{|class="wikitable"

{|class="wikitable"

|-

|-

!Coconut coir<ref>Rheaume, A., Hinman, C., and Ahearn, D. (2015). “A Synthesis of Bioretention Research in Pacific Northwest.” Herrera, <http://www.modularwetlands.com/new/wp-content/uploads/2015/11/2-Bioretention-Synthesis-2015-DAhearn.pdf></ref>

!Coconut coir<ref>Rheaume, A., Hinman, C., and Ahearn, D. (2015). “A Synthesis of Bioretention Research in Pacific Northwest.” Herrera, <http://www.modularwetlands.com/new/wp-content/uploads/2015/11/2-Bioretention-Synthesis-2015-DAhearn.pdf></ref>

|Doesn't leach phosphorus||Requires importation

|Doesn't leach phosphorus||Must be imported

|-

|-

!Wood chip

!Wood chip

|Doesn't leach phosphorus<br>Promotes nitrogen removal from water||-

|Doesn't leach phosphorus<br>Promotes nitrogen removal from water||

|-

|-

!Peat Moss

!Peat Moss

|Doesn't leach phosphorus||Sustainability controversial

|Doesn't leach phosphorus||Must be extracted from natural wetlands

|-

|-

!Shredded paper <ref>Urban Drainage and Flood Control District. (2010). “Bioretention.” <http://udfcd.org/criteria-manual/volume-3/t-03-bioretention/> (Mar. 15, 2018).</ref> (see: Pittmoss)

!Shredded paper (e.g., Pittmoss)

|Doesn't leach phosphorus<br>Promotes denitrification

|||

|||

|}

|}

===Wood derivatives===

===Wood derivatives===

The 2017 guidance from New Hampshire specifically rules against the inclusion of compost in their bioretention media.<ref>UNHSC Bioretention Soil Specification. (2017). Retrieved from https://www.unh.edu/unhsc/sites/default/files/media/unhsc_bsm_spec_2-28-17_0.pdf</ref> Instead they recommend sphagnum peat or ''"Shredded wood, wood chips, ground bark, or wood waste; of uniform texture and free of stones, sticks"''. The use of wood chip has been common in New Hampshire for some time, in this 2006 thesis 20% wood chips (not characterized) were incorporated into all of the test cases to match current practices at the time. <ref>Stone, R. M. (2013). Evaluation and Optimization of Bioretention Design for Nitrogen and Phosphorus Removal. University of New Hampshire. Retrieved from https://www.unh.edu/unhsc/sites/unh.edu.unhsc/files/STONE THESIS FINAL.pdf</ref>

The 2017 guidance from New Hampshire specifically rules against the inclusion of compost in their bioretention media.<ref>UNHSC Bioretention Soil Specification. (2017). Retrieved from https://www.unh.edu/unhsc/sites/default/files/media/unhsc_bsm_spec_2-28-17_0.pdf</ref> Instead they recommend ''"Shredded wood, wood chips, ground bark, or wood waste; of uniform texture and free of stones, sticks"''. The use of wood chip has been common in New Hampshire for some time, in this 2006 thesis 20% wood chips (not characterized) were incorporated into all of the test cases to match current practices at the time. <ref>Stone, R. M. (2013). Evaluation and Optimization of Bioretention Design for Nitrogen and Phosphorus Removal. University of New Hampshire. Retrieved from https://www.unh.edu/unhsc/sites/unh.edu.unhsc/files/STONE THESIS FINAL.pdf</ref>

Shredded paper has been tested as an additional source of carbon and as an electron-donor to promote denitrification in a number of successful laboratory and field studies.  

Shredded paper has been tested as an additional source of carbon and as an electron-donor to promote denitrification in a number of successful laboratory and field studies.  

==Additives==

==Additives==

Typically these components would make up 5- 10% by volume of the filter media mixture.  

Typically these components would make up 5 to 10% by volume of the filter media mixture.  

{{:Additives}}

{{:Additives}}

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