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Line 233: − − ===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'. 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. <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 as a result possesses a 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 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, similar to the configuration, first on the left, but instead of soil cells this tree trench 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. 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. <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>
→Design
===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'. 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. <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 as a result possesses a 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 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, similar to the configuration, first on the left, but instead of soil cells this tree trench 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. 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. <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==