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| [[File:Perforations.png|thumb|Pipes are available with perforations on just one side, these should be situated on the lower half of the pipe. Pipes with 360° perforations should have a strip of geotextile or membrane placed over the pipe to reduce the migration of fines from overlying media.]] | | [[File:Perforations.png|thumb|Pipes are available with perforations on just one side, these should be situated on the lower half of the pipe. Pipes with 360° perforations should have a strip of geotextile or membrane placed over the pipe to reduce the migration of fines from overlying media.]] |
− | Perforated pipes are a common component of [[underdrains]] used in [[bioretention]], [[permeable paving| permeable pavements]], [[infiltration trenches]] and [[exfiltration trenches| exfiltration systems]]. | + | Perforated pipes are a common component of [[underdrains]] used in [[bioretention]], [[permeable pavements]], [[infiltration trenches]] and [[exfiltration trenches| exfiltration systems]]. |
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− | Pipes should have been manufactured in conformity with the latest standards by the Canadian Standards Association (CSA) or ASTM International. | + | Pipes should be manufactured in conformity with the latest standards by the Canadian Standards Association (CSA) or ASTM International. |
− | *Perforated pipes should be continuously perforated, smooth interior HDPE (or equivalent material). | + | *Perforated pipes should be continuously perforated, smooth interior HDPE or PVC. |
− | **Wherever possible pipes should be ≥ 200 mm internal diameter to reduce potential of freezing and to facilitate inspections and maintenance with a push camera. | + | **Wherever possible pipes should be ≥200 mm internal diameter to reduce potential of freezing and to facilitate push camera inspections and cleaning with jet nozzle equipment. |
| **Smooth interior facilitates inspection and maintenance activities; internal corrugations can cause cameras or hydrojetting apparatus to become snagged. | | **Smooth interior facilitates inspection and maintenance activities; internal corrugations can cause cameras or hydrojetting apparatus to become snagged. |
| **A perforated pipe with many rectangular slots has better drainage characteristics than a pipe with similar open area provided by fewer circular holes <ref>Hazenberg, G., and U. S. Panu (1991), Theoretical analysis of flow rate into perforated drain tubes, Water Resour. Res., 27(7), 1411–1418, doi:10.1029/91WR00779.</ref>. | | **A perforated pipe with many rectangular slots has better drainage characteristics than a pipe with similar open area provided by fewer circular holes <ref>Hazenberg, G., and U. S. Panu (1991), Theoretical analysis of flow rate into perforated drain tubes, Water Resour. Res., 27(7), 1411–1418, doi:10.1029/91WR00779.</ref>. |
− | *Non-perforated pipes should be used for conveyance to and away from the facility, including [[overflow]]. It is good practice to extend the non-perforated pipe approximately 300 mm within the reservoir or practice to reduce the potential for native soil migration to clog the pipe at the interface. | + | *Non-perforated pipes should be used for conveyance of stormwater to and from the facility, including [[overflow]]. It is good practice to extend the solid pipe approximately 300 mm within the reservoir or practice to reduce the potential for native soil migration into the pipe. |
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