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Line 1: − + + + + + + + + + + + + + + + − + − They are underground stormwater conveyance systems designed to attenuate runoff volume and thereby, reduce contaminant loads to receiving waters. They are composed of perforated pipes installed in gently sloping granular stone beds that are lined with [[geotextile]] fabric that allow [[infiltration]] of runoff into the gravel bed and underlying native soil while it is being conveyed from source areas or other BMPs to an end-of-pipe facility or receiving waterbody. + + + + + + + − Exfiltration systems can be used in place of conventional storm sewer pipes, where topography, water table depth, and runoff quality conditions are suitable. They are suitable for treating runoff from roofs, walkways, parking lots and low to medium traffic roads, with adequate [[pretreatment]]. − A design variation can include perforated catchbasins, where the catchbasin sump is perforated to allow runoff to infiltrate into the underlying native soil. + − + + + + + + + + + + + + + + − + + + + + + + + + + + − + − + + + + + + + + + + + + + + + + + + + + + + + − + + + + + +
→Inspection and Maintenance
Exfiltration trenches are similar to [[infiltration trenches]] but differ primarily in the the manner in which stormwater is delivered to the trench.
<imagemap>
File:Exfitlration .gif|thumb|600px|Typical flow pathway through one section of the Etobicoke Exfiltration system (see performance report for further details) For more details click [https://sustainabletechnologies.ca/app/uploads/2013/03/Exfil_ES.pdf here.] <span style="color:red">''A 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 195 134 260 179 [[Exfiltration: Gallery|Manhole]]
rect 28 285 153 312 [[Reservoir aggregate|Clear Stone Trench]]
rect 231 366 404 386 [[Pipes|Perforated Pipe]]
rect 9 334 84 398 [[Pipes|Perforated Pipe]]
rect 319 159 416 195 [[Better site design|Storm Sewer]]
rect 399 66 467 88 [[Overflow|Catch Basin]]
</imagemap>
Exfiltration trenches are similar to [[infiltration trenches]] but differ primarily inthe 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 long infiltration trenches or linear soakaways that are designed for both conveyance and infiltration of stormwater runoff.
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.
{{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.}}
[[File:Exfilt syst.png|thumb|500px|A schematic of a standard exfiltration system integrated with conventional stormwater conveyance systems (catch basins, stormwater pipes and pipes and maintenance/manholes).]]
Take a look at the downloadable Exfiltration Trench Systems Factsheet below for a .pdf overview of this LID Best Management Practice:
Perforated pipe systems can also be referred to as pervious pipe systems, exfiltration systems, clean water collector systems and percolation drainage systems.
{{Clickable button|[[File:Exfiltration.png|150px|link=https://wiki.sustainabletechnologies.ca/images/4/4e/Exfiltration_systems_final.pdf]]}}
'''The fundamental components of an exfiltration system are:'''
*[[pretreatment| pre-treatment devices]] to retain coarse sediment, trash, debris and floatables,
*perforated [[pipes]] embedded in washed gravel connected to maintenance holes and catch basins,
*a gently sloping granular [[reservoir aggregate| storage reservoir]] below the perforated pipe.
'''Optional components include:'''
*[[Geotextile]] to prevent migration of fines into the reservoir;
*Trench plugs to help disperse stormwater throughout the trench and enhance infiltration; and
*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 also be referred to as perforated 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.
===Infiltration===
For information about constraints to infiltration practices, and approaches and tools for identifying and designing within them see [[Infiltration]].
===Native Soil===
Exfiltration trench systems 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]].
===Site Topography===
===Site Topography===
Systems cannot be located on natural slopes > 15 %.
Systems cannot be located on natural slopes > 15 %.
For more information on planning considerations and site constraints see [[Infiltration trenches]].
For a table summarizing information on planning considerations and site constraints see [[Site considerations]].
==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 600 and 2400 mm <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>. The gravel beds should have gentle slopes between 0.5 to 1%.
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]]
==Inspection and Maintenance==
Routine inspection and maintenance consists of checking and cleaning trash, debris and sediment from [[pretreatment]] devices, [[inlets]] and [[overflow|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|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. <br>
</br>
Take a look at the [[Inspection and Maintenance: Underground Infiltration Systems]] page by clicking below for further details about proper inspection and maintenance practices:
{{Clickable button|[[File:Cover page underground.PNG|150px|link=https://wiki.sustainabletechnologies.ca/wiki/Inspection_and_Maintenance:_Underground_Infiltration_System]]}}
==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
==References==
[[Category:Infiltration]]
[[Category: Green infrastructure]]