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− | {{float right|[[File:perf pipe.gif|border|600 px|Exfiltration trench under high flow and exfiltration conditions]]}} | + | {{float right|[[File:Perf pipe resize small.gif|417 × 194 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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| *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.}} |
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| + | Take a look at the downloadable Exfiltration Trench Systems Factsheet below for a .pdf overview of this LID Best Management Practice: |
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| + | {{Clickable button|[[File:Exfiltration.png|150 px|link=https://wiki.sustainabletechnologies.ca/images/4/4e/Exfiltration_systems_final.pdf]]}} |
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| '''The fundamental components of an exfiltration system are:''' | | '''The fundamental components of an exfiltration system are:''' |
| *[[pretreatment| pre-treatment devices]] to retain coarse sediment, trash, debris and floatables, | | *[[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, | | *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 that may include trench plugs. | + | *a gently sloping granular [[reservoir aggregate| storage reservoir]] below the perforated pipe. |
| '''Optional components include:''' | | '''Optional components include:''' |
| *[[Geotextile]] to prevent migration of fines into the reservoir; | | *[[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. | | *Perforated maintenance hole or catch basin risers. |
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| 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. |
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− | 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. |
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| ===Site Topography=== | | ===Site Topography=== |