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[[File:perf pipe.gif|frame|300 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.
{{textbox|Exfiltration pipe systems are an ideal technology for:
*Road retrofits where sewer lines are being replaced,
*All new road/storm sewer constructions where no constraints to infiltration exist,
*Tight urban spaces where no landscaped practices can be squeezed in, and there is a low risk tolerance for flooding.}}
'''The fundamental components of an exfiltration system are:'''
*perforated [[pipes]] connected to manholes and catchabasins,
*a gently sloping granular [[reservoir aggregate| reservoir]].
'''An additional components is:'''
*[[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]].
[[Perforated catchbasins]] are a design variation, where the sump is perforated to allow runoff to infiltrate into the underlying soil.
[[Perforated catchbasins]] are a design variation, where the sump is perforated to allow runoff to infiltrate into the underlying soil.
Exfiltration systems can also be referred to as perforated pipe systems, pervious pipe systems, clean water collector systems and percolation drainage systems.
Exfiltration systems can also be referred to as perforated pipe systems, pervious pipe systems, clean water collector systems and percolation drainage systems.
==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 %.
*Calculate maximum '''[[flow through perforated pipe]]'''
===Drawings===
Standard details for exfiltration trenches have been produced by City of Kitchener and City of Barrie. See [[Drawings]]
==Gallery==
{{:Exfiltration:_Gallery}}
==Materials==
{{:Reservoir aggregate}}
{{:Geotextiles}}
==Performance==
==Performance==
{{:Exfiltration: Performance}}
{{:Exfiltration: Performance}}
===See also===
[https://sustainabletechnologies.ca/home/urban-runoff-green-infrastructure/low-impact-development/perforated-pipe-systems/ STEP and partners research and reports on exfiltration systems]
==External resources==
==External resources==
https://www.chijournal.org/C390
*https://www.chijournal.org/C390
*http://www.civil.ryerson.ca/seminar/Papers/Draft%20Design%20manual%20of%20EES%20by%20Tran%20and%20Li%207-24-2015.pdf
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