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[[File:perf pipe.gif|thumb|500 px|Exfiltration trench under high flow and exfiltration conditions]]

{{float right|[[File:perf pipe.gif|border|600 px|Exfiltration trench under high flow and exfiltration conditions]]}}

Exfiltration trenches are similar to [[infiltration trenches]] but differ primarily in the the manner in which stormwater is delivered to the trench.<br>

Exfiltration trenches are similar to [[infiltration trenches]] but differ primarily in the the manner in which stormwater is delivered to the trench.<br>

Runoff enters infiltration trenches directly by infiltration from the surface. In exfiltration systems, surface runoff is collected by drainage [[inlets]] and delivered to the trench via subsurface perforated [[pipes]].

Runoff enters infiltration trenches directly by infiltration from the surface. In exfiltration systems, surface runoff is collected by drainage [[inlets]] and delivered to the trench via subsurface perforated [[pipes]].

Exfiltration systems can be thought of as linear soakaways; designed for both conveyance and [[infiltration]] of excess stormwater.

Exfiltration systems can be thought of as linear soakaways; designed for both conveyance and [[infiltration]] of excess stormwater.

By attenuating runoff volume, they reduce contaminant loads delivered to downstream BMPs, end-of-pipe facilities or receiving waterbodies.  

By attenuating runoff volume, they reduce contaminant loads delivered to downstream BMPs, end-of-pipe facilities or receiving waterbodies.  

They are composed of perforated [[pipes]] installed in gently sloping granular stone beds, lined with [[Geotextiles|geotextile]] fabric.  

*Road retrofits where sewer lines are being replaced,

'''The fundamental components of an exfiltration system are:'''

*perforated [[pipes]] connected to manholes and catchabasins,

*a gently sloping granular [[reservoir aggregate| reservoir]].

*[[Geotextile]] to prevent migration of fines into the reservoir.  

Exfiltration systems can be used in place of conventional storm sewer pipes, where topography, water table depth, and [[water quality]] conditions are suitable. They are suitable for treating runoff from roofs, walkways, parking lots and low to medium traffic roads, with adequate [[pretreatment]].  

Exfiltration systems can be used in place of conventional storm sewer pipes, where topography, water table depth, and [[water quality]] conditions are suitable. They are suitable for treating runoff from roofs, walkways, parking lots and low to medium traffic roads, with adequate [[pretreatment]].  

==Design==

==Design==

===Geometry and Site Layout===

===Geometry and Site Layout===

Gravel beds in which exfiltration systems are installed are typically rectangular excavations with a bottom width between 0.6 and 2.4 m <ref>Greater Vancouver Regional District. 2005. Stormwater Source Control Design

*Gravel beds in which exfiltration systems are installed are typically rectangular excavations with a bottom width between 0.6 and 2.4 m <ref>Greater Vancouver Regional District. 2005. Stormwater Source Control Design

Guidelines 2005. Prepared by Lanarc Consultants Limited, Kerr Wood Leidal Associates Limited and Goya Ngan</ref>.  

Guidelines 2005. Prepared by Lanarc Consultants Limited, Kerr Wood Leidal Associates Limited and Goya Ngan</ref>.  

The gravel beds should have gentle slopes between 0.5 - 1%.

Standard details for exfiltration trenches have been produced by City of Kitchener and City of Barrie. See [[Drawings]]

 

==Performance==

==Performance==

{{:Exfiltration: Performance}}

{{:Exfiltration: Performance}}

==External resources==

==External resources==

https://www.chijournal.org/C390

*https://www.chijournal.org/C390

 

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