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Line 233: − − ===Variations of Stormwater Tree Trenches=== − − [[File:Stormwater Tree Trench low permeability native subsoil with structural soil medium.png|thumb|left|450px|'''Tree Trench with High Permeability Subsoil, with Structural Soil Medium''' - This tree trench configuration possess low permeability soil ([[Soil groups]] C or D), along with a clean-out stand pipe for the underdrain, which is placed lower in the feature to allow water to infiltrate into the system and remove contaminants from the road/sidewalk before being taken up by the tree or transported out of the feature and back into the storm sewer system. It also contains structural soil, which is an engineered medium that can be compacted to support sidewalks, while also creating extra space for suitable tree root growth under paved surfaces. This space allows the tree to mature unimpeded and cuts down on replacement costs for tree removal and maintenance costs of the surrounding sidewalk and road.]] − − [[File:Stormwater Tree Trench high permeability native subsoil with structural soil medium.png|thumb|right|450px|'''Tree Trench with Low Permeability Subsoil, with Soil Cells''' - This tree trench configuration possess high permeability soil ([[Soil groups]] A or B), and as a result possesses a clean-out stand pipe/clean-out for the underdrain, which is placed higher in the feature as water will infiltrate through the system much quicker. This allows for further infiltration into the system into the underlying native soil below. Once water has percolated through the soil to the perforated underdrain it is then transported out of the feature and back into the storm sewer system. This configuration also includes a monitoring well to monitor water level in the feature below the aggregate line at the bottom of the feature. This feature contains structural soil, similar to the low permeability configuration.]] − − [[File:Stormwater Tree Trench high permeability native subsoil with soil cells.png|thumb|center|450px|'''Tree Trench with High Permeability Subsoil, with Soil Cells''' - This tree trench configuration possess high permeability soil, similar to the configuration on the right, but instead of structural soil this tree trench contains soil cells or 'modular soil support systems'. Soil cells are an alternative to structural soil media and are used adjacent to tree pits to provide room for tree roots to spread out under paved surfaces surrounding the tree trench. The growing media in soil cells typically has higher organic content than structural soils and with a looser structure and higher nutrient content of the soil, these support systems provide the most favourable environment for healthy tree growth in the urban setting.]] Line 251:
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Line 286: + + − ===Inlets=== − Multiple methods for distribution and conveyance of runoff into the system are recommended for redundancy and conservative designs. − Combinations may be made of: − *tree well flow, − *catchbasins and distribution pipes, and − *direct infiltration from permeable paving. − See also [[Inlets]] and [[pretreatment]] − − ===Species selection=== − − For a detailed overview with in-depth information on species selection please visit our [[Plant lists]] wiki page and you can continue on to our further detailed tables showcasing how to develop planting plans that include selection of species for specific functions in several stormwater tree trenches and other LID practices. − − *[[Trees: List]] − *[[Shrubs: List]] − *[[Perennials: List]] − *[[Graminoids: List]] − − ===Planting pit sizing=== − [[Bioretention: Sizing]] Line 327:
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→Variations of Stormwater Tree Trenches
<imagemap>
<imagemap>
File:SWTT Struct Pan High Perm Final crop.png|thumb|500 px|A Stormwater tree trench with structural concrete panels and soil cells. A structural concrete panel configuration is an alternative to modular soil support systems that uses a “bridge deck” over bioretention/growing media that extends into the pedestrian clearway, and is supported on each side by concrete supports and compacted granular material. The benefits to this configuration is increased infiltration due to the extra provided modular support, therefore no compaction of the underlying drainage material is required. <span style="color:red">''A note: The following is an "image map", feel free to explore the image with your cursor and click on highlighted labels that appear to take you to corresponding pages on the Wiki.''</span>
File:SWTT Struct Pan High Perm Final crop.png|thumb|500 px|'''A Stormwater tree trench with structural concrete panels and soil cells.''' A structural concrete panel configuration is an alternative to modular soil support systems that uses a “bridge deck” over bioretention/growing media that extends into the pedestrian clearway, and is supported on each side by concrete supports and compacted granular material. The benefits to this configuration is increased infiltration due to the extra provided modular support, therefore no compaction of the underlying drainage material is required. <span style="color:red">'''''Note:''' The following is an "image map", feel free to explore the image with your cursor and click on highlighted labels that appear to take you to corresponding pages on the Wiki.''</span>
rect 1632 3032 1696 3394 [[Overflow|Overflow to Underdrain]]
rect 1632 3032 1696 3394 [[Overflow|Overflow to Underdrain]]
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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.
They also provide road and walkway drainage, contribute to stormwater pollutant removal and decrease the volume of urban runoff entering local waterways. They feature trees, soil, stormwater inlet and outlet structures, distribution and drainage pipes, and may include soil support structures, structural soil medium or structural concrete panels (as seen in the image map to the right). The tree planting pits and adjacent supported sidewalk pavements provide more soil volume for tree growth and water retention.
They also provide road and walkway drainage, contribute to stormwater pollutant removal and decrease the volume of urban runoff entering local waterways. They feature trees, soil, stormwater inlet and outlet structures, distribution and drainage pipes, and may include soil support structures, structural soil medium or structural concrete panels (as seen in the image map to the right). The tree planting pits and adjacent supported sidewalk pavements provide more soil volume for tree growth and water retention.
'''Stormwater tree trench installations include:'''
'''Stormwater tree trench installations include:'''
* Overlying impermeable or [[permeable pavements]]
* Trees (tolerant to northern. urban conditions)
* Trees (tolerant to northern. urban conditions)
* Planting soil
* Planting soil
* Structural soil
* Modular soil support or "soil cell" structures (optional)
* Stormwater inlet and outlet structures,
* Structural soil (optional)
* Structural concrete panels (optional)
* Stormwater inlet and outlet structures
* Distribution and drainage pipes
* Distribution and drainage pipes
* Mulch
* [[Choker layer]] (optional)
* Aggregate Base
* Geogrid and geotextile (optional)
* Choker layer
* [[Reservoir aggregate|Aggregate base]]
'''Additional components may include:'''
'''Additional components may include:'''
* an underdrain system
* [[Bioretention: Internal water storage|Internal water storage]] layer
* various configurations of soil cell additions
* Distribution and [[underdrain]] pipe access and clean-out features
* geotextile fabric around soil cell structures
* [[Wells|Monitoring well]] screened within internal water storage layer
* impermeable geomembrane on sites where soil infiltration is not desired
* Root barriers in locations where tree rooting is not desired
==Planning considerations==
==Planning considerations==
Designers should consult local utility design guidance for the horizontal and vertical clearances required.
Designers should consult local utility design guidance for the horizontal and vertical clearances required.
===Karst===
===[[Karst]]===
Tree trenches designed to drain primarily by infiltration are unsuitable in areas of known or implied karst topography.
Tree trenches designed to drain primarily by infiltration are unsuitable in areas of known or implied karst topography.
===Distribution and Underdrain pipes===
===Distribution and Underdrain pipes===
To maximize the quantity of growing or structural soil medium irrigated, distribution pipes should be installed flat, just below modular soil support tops or at the top of the structural soil media layer and in both tree pit and supported pavement portions of the trench. Pipe perforations should be oriented to the sides and section ends should be sealed with a solid cap. To enhance runoff volume reduction underdrain pipes can be installed above the bottom of the trench and/or include flow control. Alternatively, the underdrain pipe may be installed on trench bottom and connected to a riser assembly in the outlet manhole. It is critical to include connections to outlet storm sewer pipes and multiple cleanout access points.
To maximize the quantity of growing or structural soil medium irrigated, distribution pipes should be installed flat, just below modular soil support tops or at the top of the structural soil media layer and in both tree pit and supported pavement portions of the trench. Pipe perforations should be oriented to the sides and section ends should be sealed with a solid cap. To enhance runoff volume reduction underdrain pipes can be installed above the bottom of the trench and/or include flow control. Alternatively, the underdrain pipe may be installed on trench bottom and connected to a riser assembly in the outlet manhole. It is critical to include connections to outlet storm sewer pipes and multiple cleanout access points.
===Variations of Stormwater Tree Trenches===
Below, find three alternate stormwater tree trench configurations, that differ based off of native subgrade soil permeability and associated infiltration rates, structural support systems used (modular soil cell systems vs. structural soil medium) and placement of the underdrain for the system based off of these factors. All the images below are partial image map drawings, which only feature interactive differing specifications with highlighted labels that appear to take you to corresponding pages on the Wiki tare not found in the image map at the top of the page, highlighting features of a Stormwater tree trench with structural concrete panels and soil cells.
<imagemap>
File:SWTT Low Perm Soil Cells Final.png|thumb|left|450px|'''Tree trench with soil cells on low permeability subsoil''' - This tree trench configuration possess low permeability soil ([[Soil groups]] C or D), along with a clean-out stand pipe for the underdrain, which is placed lower in the feature to allow water to infiltrate into the system and remove contaminants from the road/sidewalk before being taken up by the tree or transported out of the feature and back into the storm sewer system. It also includes soil cells or 'modular soil support systems'. <span style="color:red">'''''Note''': The following is an "image map", feel free to explore the image with your cursor and click on highlighted labels that appear to take you to corresponding pages on the Wiki.''</span>
rect 951 3681 1591 3739 [[Soil groups|Uncompacted Subgrade Soil]]
rect 1596 3684 1996 3737 [[Soil groups|Compacted Subgrade Soil]]
rect 1605 3079 1983 3500 [[Soil cells: Gallery|Soil Cells]]
</imagemap>
<imagemap>
File:SWTT High Perm Soil Cells Final.png|thumb|right|450px|'''Tree trench with soil cells on high permeability subsoil''' - This tree trench configuration possess high permeability soil ([[Soil groups]] A or B) and possesses a stand pipe/clean-out for the underdrain, which is placed higher in the feature to allow for further infiltration into underlying native soil below. This configuration also includes a monitoring well to monitor water level in the feature below the aggregate line at the bottom of the feature. It also contains soil cells similar to the low permeability configuration. <span style="color:red">'''''Note''': The following is an "image map", feel free to explore the image with your cursor and click on highlighted labels that appear to take you to corresponding pages on the Wiki.''</span>
rect 1534 3458 1576 3737 [[Stormwater Tree Trenches|Water Storage Depth]]
rect 951 3681 1591 3739 [[Soil groups|Uncompacted Subgrade Soil]]
rect 1596 3684 1996 3737 [[Soil groups|Compacted Subgrade Soil]]
rect 1605 3079 1983 3500 [[Soil cells: Gallery|Soil Cells]]
rect 1070 3001 1122 3688 [[Wells|Monitoring Well]]
</imagemap>
<imagemap>
File:SWTT Struct Soil Med High Perm Final.png|thumb|center|450px|'''Tree Trench with structural soil medium on high permeability subsoil''' - This tree trench configuration possess high permeability soil, but instead of soil cells this tree trench contains a structural soil medium. Once water has percolated through the soil to the perforated underdrain it is then transported out of the feature and back into the storm sewer system. This configuration also includes a monitoring well below the aggregate line at the bottom of the feature. <span style="color:red">'''''Note''': The following is an "image map", feel free to explore the image with your cursor and click on highlighted labels that appear to take you to corresponding pages on the Wiki.''</span>
rect 1534 3458 1576 3737 [[Stormwater Tree Trenches|Water Storage Depth]]
rect 951 3681 1591 3739 [[Soil groups|Uncompacted Subgrade Soil]]
rect 1596 3684 1996 3737 [[Soil groups|Compacted Subgrade Soil]]
rect 1070 3001 1122 3688 [[Wells|Monitoring Well]]
rect 1605 3079 1983 3500 [[Stormwater Tree Trenches: Specifications|Structural Soil Medium]]
</imagemap>
* Solid pipe from inlet structures should transition to perforated pipe once 300 mm inside the trench.
* Solid pipe from inlet structures should transition to perforated pipe once 300 mm inside the trench.
* Perforated pipe should be minimum 150 mm dia. rigid, smooth interior wall HDPE or PVC with perforations on sides, wrapped with geotextile sock, with capacity and perforation specifications confirmed by the designing Engineer based on hydraulic requirements.
* Perforated pipe should be minimum 150 mm dia. rigid, smooth interior wall HDPE or PVC with perforations on sides, wrapped with geotextile sock, with capacity and perforation specifications confirmed by the designing Engineer based on hydraulic requirements.
==Inspection and Maintenance==
==Inspection and Maintenance==
At right is a list of trees that are known to tolerate conditions in northern (Zone 3) urban stormwater tree trenches.
At right is a list of trees that are known to tolerate conditions in northern (Zone 3) urban stormwater tree trenches.
===Species selection===
For a detailed overview with in-depth information on species selection please visit our [[Plant lists]] wiki page and you can continue on to our further detailed tables showcasing how to develop planting plans that include selection of species for specific functions in several stormwater tree trenches and other LID practices.
*[[Trees: List]]
*[[Shrubs: List]]
*[[Perennials: List]]
*[[Graminoids: List]]
==Soil cells==
==Soil cells==
*If the system is unlined it is hydraulically equivalent to a [[bioretention]] cell and provides similar water quality benefits.
*If the system is unlined it is hydraulically equivalent to a [[bioretention]] cell and provides similar water quality benefits.
*If the system is lined and underdrained it is hydraulically similar to a large [[stormwater planter]]. Depending on the design detail it may retain significant stormwater within the planting soil volume and will provide water quality benefits.
*If the system is lined and underdrained it is hydraulically similar to a large [[stormwater planter]]. Depending on the design detail it may retain significant stormwater within the planting soil volume and will provide water quality benefits.
*Structures are designed to be filled with growing medium for tree rooting and support a vehicle loaded pavement up to and including AASHTO H-20 and Ontario Building Code standards for sidewalks.
*Critical to modular soil support system design is that each structure or layer of structures be independent of all adjacent ones, such that one or multiple layers can be removed to facilitate future utility installation or repair.
[[File:DepressedDrain_SoilCell.png|thumb|500px|A surface [[inlets|inlet]] configuration featuring a depressed drain routing water collected from the street to an enclosed area infiltrating water to soil cells underneath.]]
[[File:DepressedDrain_SoilCell.png|thumb|500px|A surface [[inlets|inlet]] configuration featuring a depressed drain routing water collected from the street to an enclosed area infiltrating water to soil cells underneath.]]
===Underdrain===
===Underdrain===
==Galleries==
==Galleries==
===Open tree pits===
===Open tree pits===
{{:Extended tree pits: Gallery}}
{{:Extended tree pits: Gallery}}
*[https://www.storm-tree.com Storm-Tree]
*[https://www.storm-tree.com Storm-Tree]
==References==
Also see references as direct web page links above.
[[Category:Green infrastructure]]
[[Category:Green infrastructure]]