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

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

|< 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 D6913/D6913M, Standard Test Methods for Particle-Size Distribution (Gradation) of Soils Using Sieve Analysis; and <br>

|< 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 D6913/D6913M, Standard Test Methods for Particle-Size Distribution (Gradation) of Soils Using Sieve Analysis (pebble to sand fraction); and <br>

ASTM D7928, Standard Test Method for Particle-Size Distribution (Gradation) of Fine-Grained Soils Using the Sedimentation (Hydrometer) Analysis.|-

ASTM D7928, Standard Test Method for Particle-Size Distribution (Gradation) of Fine-Grained Soils Using the Sedimentation (Hydrometer) Analysis (silt and clay fraction).

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

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

|3 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.

   

   

===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 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]] is the most widely used organic component. It's use in bioretention facilities is well established and documented. In Ontario, compost should comply with mandatory Ontario Compost Quality Standards for Category 'AA'.<ref>Ontario Ministry of the Environment and Climate Change (OMOECC). 2012. Ontario Compost Quality

http://www.alcanada.com/index_htm_files/compost_handbook.pdf.</ref> Low available phosphorus composts should always be sought for use in low impact development facilities, including bioretention. Low available phosphorus composts 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>

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:

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, or an [[Additives| additive]] to enhance nutrient retention of the media should also be included in the blend, or a layer be included above the stone reservoir, or a reactive media vault be included in the treatment train downstream of the bioretention (see Additive below for available options). 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"

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!Peat moss

!Peat moss

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

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

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!Shredded paper (e.g., Pittmoss)

!Shredded paper (e.g., Pittmoss)