Pipes

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, infiltration trenches and exfiltration trenches.

Pipes should have been 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).
  • Wherever possible pipes should be ≥ 200 mm internal diameter to reduce clogging and to facilitate inspections and maintenance.
  • 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 .
• 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 chance of migration from native soils clogging the pipe at the interface.

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  Pipe with slotted perforations

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  Perforated pipes awaiting installation, note the 30 degree connector used to facilitate maintenance.

See also: flow through perforated pipe

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Filter fabric that is installed to separate dissimilar soils and provide runoff filtration and contaminant removal benefits while maintaining a suitable rate of flow; may be used to prevent fine-textured soil from entering a coarse granular bed, or to prevent coarse granular from being compressed into underlying finer-textured soils.

Soil particles with a diameter less than 0.050 mm.