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This article is about underground systems which distribute concentrated flow along a level, linear facility to promote infiltration to native soils. <br>

This article is about underground systems which distribute concentrated flow along a level, linear facility to promote infiltration to native soils. <br>

See [[exfiltration trenches]] for guidance on infiltration trench systems integrated with conventional storm sewers and manholes that provide both infiltration and conveyance functions.  

See [[exfiltration trenches]] for guidance on infiltration trench systems integrated with conventional storm sewers and manholes that provide both infiltration and conveyance functions.  

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==Overview==

==Overview==

[[File:Infiltration Trench.png|thumb|Images and schematic depicting residential infiltration trenches that when installed help reduce the risk of flooding and limit negative impacts to stormwater quality.<ref>The City of Windsor. Stormwater Solutions: Infiltration Trenches. https://www.citywindsor.ca/residents/environment/climate-change-adaptation/climate-resilient-home/Documents/Infiltration%20Trench.pdf. Updated 2021. Accessed 30 August, 2021</ref>]]

[[File:Infiltration Trench.png|450px|thumb|Images and schematic depicting residential infiltration trenches, commonly referred to as [[soakaways]], that when installed help reduce the risk of flooding and limit negative impacts to stormwater quality.<ref>The City of Windsor. Stormwater Solutions: Infiltration Trenches. https://www.citywindsor.ca/residents/environment/climate-change-adaptation/climate-resilient-home/Documents/Infiltration%20Trench.pdf. Updated 2021. Accessed 30 August, 2021</ref>]]

Infiltration trenches are underground, linear, rectangular or trapezoidal excavations with level or gently sloping bottom grade, geotextile filter fabric on sidewalls and top and filled with clean, crushed angular stone or other void-forming structures. They are well suited to sites where available space for infiltration is limited to strips of land between buildings or properties, or along road rights-of-way. They can also be referred to as infiltration galleries. See [[Perforated Pipe Systems]] fact sheet for guidance on infiltration trench systems integrated with conventional storm sewers that provide both infiltration and conveyance functions.

Infiltration trenches are underground, linear, rectangular or trapezoidal excavations with level or gently sloping bottom grade, geotextile filter fabric on sidewalls and top and filled with clean, crushed angular stone or other void-forming structures. They are well suited to sites where available space for infiltration is limited to strips of land between buildings or properties, or along road rights-of-way. They can also be referred to as infiltration galleries. See [[Exfiltration trenches]] fact sheet for guidance on infiltration trench systems integrated with conventional storm sewers that provide both infiltration and conveyance functions.

{{textbox|1=Infiltration trenches are an ideal technology for:  

{{textbox|1=Infiltration trenches are an ideal technology for:  

*Installing below any type of surface or landscape

*Installing below any type of surface or landscape

*Balancing the requirements to infiltrate excess stormwater whilst conveying excess}}

*Balancing the requirements to infiltrate excess stormwater whilst conveying excess}}

'''The fundamental components of an infiltration trench are:'''  

'''The fundamental components of an infiltration trench are:'''  

*Water storage reservoir, filled with [[Reservoir_gravel|coarse aggregate]], possibly void-forming structures to minimize depth and conserve aggregate, and organic material derived from untreated wood (aids in dissolved nitrogen removal);

*Water storage reservoir, filled with [[Reservoir_gravel|coarse aggregate]], possibly void-forming structures to minimize depth and conserve aggregate, and organic material derived from untreated wood (aids in dissolved nitrogen removal);

*Plastic chambers usually have a parabolic shape to support the load above. The spaces between rows of plastic pipes or chambers are filled with clear stone to support overlying structures.

*Plastic chambers usually have a parabolic shape to support the load above. The spaces between rows of plastic pipes or chambers are filled with clear stone to support overlying structures.

*Concrete vaults and plastic crates are often rectangular-shaped. Concrete vault systems can, in some circumstances, be employed without any additional cover. However, a minimum of 20 cm cover is recommended for most applications. Where this cover is planting soil this can support turf grass. Greater planting soil depths are required to support more deeply rooting plants like perennials and shrubs (45 to 60 cm) and trees (85 to 100 cm).

*Concrete vaults and plastic crates are often rectangular-shaped. Concrete vault systems can, in some circumstances, be employed without any additional cover. However, a minimum of 20 cm cover is recommended for most applications. Where this cover is planting soil this can support turf grass. Greater planting soil depths are required to support more deeply rooting plants like perennials and shrubs (45 to 60 cm) and trees (85 to 100 cm).

===Native Soil===

===Native Soil===

Infiltration trenches, chambers and soakaways can be constructed over any soil type, but hydrologic soil group (HSG) A or B soils are best for achieving water balance and erosion control objectives. Facilities should be located on portions of the site with the highest infiltration rates. Native soil infiltration rate at the proposed facility location and depth should be confirmed through in-situ measurements of hydraulic conductivity under field saturated conditions.  

Infiltration trenches, chambers and soakaways can be constructed over any soil type, but hydrologic soil group (HSG) A or B soils are best for achieving water balance and erosion control objectives. Facilities should be located on portions of the site with the highest infiltration rates. Native soil infiltration rate at the proposed facility location and depth should be confirmed through in-situ measurements of hydraulic conductivity under field saturated conditions. For guidance on infiltration testing and selecting a design infiltration rate see [[Design infiltration rate]].

===Wellhead Protection===

===Wellhead Protection===

===Water Table===

===Water Table===

Maintaining a separation of one (1) metre between the elevations of the base of the practice and the seasonally high water table, or top of bedrock is recommended. Lesser or greater values may be considered based on groundwater mounding analysis. See STEP LID Planning and Design Guide wiki page, [[Groundwater]] for further guidance and spreadsheet tool.

Maintaining a separation of one (1) metre between the elevations of the base of the practice and the seasonally high water table, or top of bedrock is recommended. Lesser or greater values may be considered based on groundwater mounding analysis. See [[Groundwater]] for further guidance and spreadsheet tool.

===Pollution Hot Spot Runoff===

===Pollution Hot Spot Runoff===

Designers should consult local utility design guidance for the horizontal and vertical clearances required between storm drains.

Designers should consult local utility design guidance for the horizontal and vertical clearances required between storm drains.

===Karst===

===[[Karst]]===

Infiltration trenches, chambers and soakaways are not suitable in areas of known or implied karst topography.  

Infiltration trenches, chambers and soakaways are not suitable in areas of known or implied karst topography.

===Setback from Buildings===

===Setback from Buildings===

Facilities should be setback a minimum of four (4) metres from building foundations.

Facilities should be setback a minimum of four (4) metres from building foundations.

==Design==

==Design==

===Monitoring Wells===  

===Monitoring Wells===  

Recommended for monitoring drainage time between storms.  Monitoring well should be a vertical standpipe consisting of an anchored 100 to 150 mm diameter pipe with perforations along the length within the reservoir, installed to the bottom of the facility, with a lockable cap. Flow-splitting manholes may also be used for drainage time monitoring.

Recommended for monitoring drainage time between storms.  Monitoring wells should be a vertical standpipe consisting of an anchored 100 to 150 mm diameter pipe with perforations along the length within the reservoir, installed to the bottom of the facility, with a lockable cap. Flow-splitting manholes may also be used for drainage time monitoring.

[[File:Monitoring_well.gif]]

[[File:Monitoring_well.gif]]

|| Yes || Yes || Yes

|| Yes || Yes || Yes

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==Materials==

==Materials==

Infiltration practice locations should not be used as sediment basins during construction. To prevent sediment from clogging, erosion and sediment controls should remain in place and runoff should be diverted from the infiltration facility until the contributing drainage area is fully stabilized and sediment removal from catch basins, pre-treatment devices and maintenance hole sumps has been completed.   

Infiltration practice locations should not be used as sediment basins during construction. To prevent sediment from clogging, erosion and sediment controls should remain in place and runoff should be diverted from the infiltration facility until the contributing drainage area is fully stabilized and sediment removal from catch basins, pre-treatment devices and maintenance hole sumps has been completed.   

===Operation and Maintenance===  

==Inspection and Maintenance==  

Infiltration trenches, chambers and soakaways will continue to function during winter months if the overflow outlet is located below the local maximum frost penetration depth (i.e. frost line).  

Infiltration trenches, chambers and soakaways will continue to function during winter months if the overflow outlet is located below the local maximum frost penetration depth (i.e. frost line).  

Routine inspection and maintenance consists of checking and cleaning trash, debris and sediment from pre-treatment devices, inlets and outlets twice a year in the spring and/or late fall, or when pre-treatment device sump is half full. Use hydro-vac truck to remove sediment from catch basin sumps, OGS and isolated chamber row filter pre-treatment devices.  To clean isolated chamber row filters use a vacuum truck equipped with rear-facing jet nozzle for cleaning large diameter pipes or culverts.  

Routine inspection and maintenance consists of checking and cleaning trash, debris and sediment from pre-treatment devices, inlets and outlets twice a year in the spring and/or late fall, or when pretreatment device sump is half full. Use hydro-vac truck to remove sediment from catch basin sumps, OGS and isolated chamber row filter pre-treatment devices.  To clean isolated chamber row filters use a vacuum truck equipped with rear-facing jet nozzle for cleaning large diameter pipes or culverts.  

 

 

 

Monitoring of storage reservoir water level during and after natural or simulated storm events using the monitoring well should be performed periodically to verify the facility drains within the required drainage time (typically 72 hours). Should be performed as part of inspections following construction or major rehabilitation prior to assumption, and every 15 years at a minimum, to track drainage performance over time and determine when replacement is needed.

{{Clickable button|[[File:Cover page underground.PNG|150 px|link=https://wiki.sustainabletechnologies.ca/wiki/Inspection_and_Maintenance:_Underground_Infiltration_Systems]]}}

See also *[[Construction]]

See also *[[Construction]]

==Gallery==

==Gallery==

{{:Infiltration trenches: Gallery}}

{{:Infiltration trenches: Gallery}}

[[category:infiltration]]

[[Category:Infiltration]]

[[Category: Green infrastructure]]