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Line 3: − + − + − **Perforations should be made on all sides of the pipe and provide a ≥ 1 m<sup>2</sup> 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. − + +
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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 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.
*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.
**Smooth interior facilitates inspection and maintenance activities; internal corrugations can cause cameras or hydrojetting apparatus to become snagged.
*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 m<sup>2</sup> of open area per linear meter of pipe.
*Non-perforated pipes should be used for conveyance to and away from the facility, including overflow.
*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).
*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>.
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[[Category:Materials]]
[[Category:Materials]]