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==Overview==
==Overview==
Stormwater tree trenches are linear tree planting structures that feature supported impermeable or [[permeable pavements]] that promote healthy tree growth while also helping to manage runoff. They are often located behind the curb within the road right-of-way and consist of subsurface trenches filled with modular structures and growing medium, or structurally engineered soil medium, supporting an overlying sidewalk pavement. They improve tree health by providing access to soil, air and stormwater for irrigation, allowing them to survive longer in harsh urban conditions.
Stormwater tree trenches are linear tree planting structures that feature supported impermeable or [[permeable pavements]] that promote healthy tree growth while also helping to manage runoff. They are often located behind the curb within the road right-of-way and consist of subsurface trenches filled with modular structures and growing medium, or structurally engineered soil medium, supporting an overlying sidewalk pavement. They improve tree health by providing access to soil, air and stormwater for irrigation, allowing them to survive longer in harsh urban conditions.
*[[Geotextiles]] are used with structural soils to prevent migration of fines from the road or sidewalk base into the structural soils. In BC, a Nilex 4545 fabric is used for this purpose, but other fabrics may also be suitable.
*[[Geotextiles]] are used with structural soils to prevent migration of fines from the road or sidewalk base into the structural soils. In BC, a Nilex 4545 fabric is used for this purpose, but other fabrics may also be suitable.
*Compaction to 95% SPD is achieved in 1 m lifts to 95% SPD. Testing of compaction of levels is accomplished with a trolled nuclear densometer for larger rock size mixes.
*Compaction to 95% SPD is achieved in 1 m lifts to 95% SPD. Testing of compaction of levels is accomplished with a trolled nuclear densometer for larger rock size mixes.
====Structural Soil Comparisons====
{|class="wikitable"
|+Specifications for Stormwater Tree Trenches using Structural Soils
|-
!Structural Soil Type
!Median Stone size/range
!Soil Texture
!Tackifiying Agent
!Approximate Porosity
|-
|'''[https://gailmaterials.net/wp-content/uploads/2019/08/cu-structural_soil_specifications.pdf CU-Soil™]'''
|30mm (20-40mm)*
|
Gravel: <5%<br>
Sand: 20-45%<br>
Silt: 20-50%<br>
Clay: 20-40%<br>
Cation Exchange Capacity (CEC) >10<br>
pH: 5.5 – 6.5<br>
Organic Content: 2 – 5% by dry weight
|[http://www.amereq.com/pages/12/index.htm Hydrogel (coated potassium propenoate-propenamide copolymer)]
|26%
|-
|'''B.C Soil'''
|75mm/60 – 80mm)
|
Sand: 45-55%<br>
Silt: 25-35%<br>
Clay: 0 – 10%<br>
Silt + Clay: 25 – 45%<br>
pH: 6.0 – 7.0<br>
Organic Content: 15-20%**
|[http://www.stabilizersolutions.com/products/stabilizer/ Stabilizer]
|33%
|-
| colspan="5" style="text-align: left;" |<small>'''Note:'''<br>
"*" = Larger or smaller stone sizes are accepted as long as they do not comprise more than 10% above or 10% below the indicated range.<br>
"**" = Soil texture is the City of Vancouver specification for structural soils</small>
|}
===Modular Soil Support Systems===
===Modular Soil Support Systems===