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.

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) with a minimum inside diameter of 100 mm.
  • Where freezing is a concern, horizontal underdrain pipes should be over-sized to a minimum 200 mm diameter.
  • Perforations should be made on all sides of the pipe and provide a ≥ 1 m² of open area per linear meter of pipe.
• All underdrains should be capped on the upstream end.
• At least one vertical well per BMP is recommended, for inspection and monitoring water level.
  • Well(s), of 100 - 150 mm diameter perforated pipe, should extend to the bottom of the facility.
  • Where a horizontal underdrain is being installed, an upstream and a downstream well should be coupled to the underdrain pipe. The pair of wells can then be used to flush out the length of underdrain if required.
  • The exposed tops of all wells should be fitted with lockable caps.
• Non-perforated pipes should be used for conveyance to and away from the facility, including overflow.
  • To function correctly, the capacity of the overflow pipes must be greater than the inlet(s).

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.

A perforated pipe used to assist the draining of soils.

Best management practice. State of the art methods or techniques used to manage the quantity and improve the quality of wet weather flow. BMPs include: source, conveyance and end-of-pipe controls.