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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]].

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==Overview==

==Overview==

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 infiltration trenches that are integrated with conventional stormwater conveyance systems (i.e. catch basins, solid pipes and maintenance holes), 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|Rainwater harvesting is an ideal technology for:  

{{textbox|Exfiltration pipe systems are an ideal technology for:  

*Road retrofits where sewer lines are being replaced,  

*Road retrofits where sewer lines are being replaced,  

*All new road/storm sewer constructions where no constraints to infiltration exist,  

*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.}}

*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:'''

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

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

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

*perforated [[pipes]] embedded in washed gravel connected to maintenance holes and catch basins,

'''An additional components is:'''

*a gently sloping granular [[reservoir aggregate| storage reservoir]] below the perforated pipe.  

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

'''Optional components include:'''

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

*Perforated maintenance hole or catch basin risers.  

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]].  

Exfiltration systems can also be referred to as perforated 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.

==Planning==

==Planning==

If properly located, designed and maintained, perforated pipe systems can greatly reduce runoff volume while having little or no surface footprint, which helps to conserve highly valued developable land.

If properly located, designed and maintained, perforated pipe systems can greatly reduce runoff volume while having little or no surface footprint, which helps to conserve highly valued developable land.

Systems should be located below shoulders of roadways, [[permeable paving]] or [[swales]] where they can be readily excavated for servicing. An adequate subsurface area outside of the 4 m setback from building foundations and suitable distance from other underground utilities must be available.

Systems should be located below shoulders of roadways, [[permeable pavements]] or [[swales]] where they can be readily excavated for servicing. An adequate subsurface area outside of the 4 m setback from building foundations and suitable distance from other underground utilities must be available.

===Site Topography===  

===Site Topography===  

*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%.

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

*Calculate maximum '''[[flow through perforated pipe]]'''

*Calculate maximum '''[[flow through perforated pipe]]'''

===Drawings===

===Drawings===

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

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

==Materials==

==Materials==

==Performance==

==Performance==

{{:Exfiltration: Performance}}

{{:Exfiltration: Performance}}

==External resources==

==External resources==