Changes

==Underdrains for infiltrating practices==

==Underdrains for infiltrating practices==

The perforated pipe within the drain should be elevated from the base to promote infiltration of the water stored beneath. The depth of this [[Bioretention: Internal_water_storage| internal water storage reservoir]] should be sized to capture and infiltrate the design storm event runoff volume based on the desired [[drainage time]] and the [[design infiltration rate]] of the native soils below. An alternative design configuration is to install the perforated pipe on the base of the practice and using an upturned outflow pipe to permit the required head of water to be stored.  

The perforated pipe within the drain should be elevated from the base to promote infiltration of the water stored beneath. The depth of this [[Bioretention: Internal_water_storage| internal water storage reservoir]] should be sized to capture and infiltrate the design storm event runoff volume based on the desired [[drainage time]] and the [[design infiltration rate]] of the native soils below. An alternative design configuration is to install the perforated pipe on the base of the practice and using an upturned outflow pipe to permit the required head of water to be stored.  

*Underdrain access structures, which may be maintenance holes or vertical standpipes connected to the perforated pipe, must be included in the design for periodic inspection and flushing of the perforated pipe. Negotiating 90 degree bends will be troublesome for most push camera and jet nozzle cleaning equipment, so it is preferable that 45 degree pipe couplings be used instead.  

*Underdrain access structures/cleanouts, which may be maintenance holes or vertical standpipes connected to the perforated pipe, must be included in the design for periodic inspection and flushing of the perforated pipe. Negotiating 90 degree bends will be troublesome for most push camera and jet nozzle cleaning equipment, so it is preferable that 45 degree pipe couplings be used instead.  

 

 

{| class="wikitable"

{| class="wikitable"

|+Clean out spacing<ref>Province of Ontario. (2018). O. Reg. 332/12: BUILDING CODE. Retrieved February 23, 2018, from https://www.ontario.ca/laws/regulation/120332</ref>

|+Clean out spacing<ref>Province of Ontario. (2022). O. Reg. 332/12: BUILDING CODE. Retrieved February 23, 2018, from https://www.ontario.ca/laws/regulation/120332</ref>

|-

|-

! Pipe internal diameter (mm)

! Pipe internal diameter (mm)

|}

|}

In some cases where the underdrain layer has sufficient depth to accommodate it, a larger diameter perforated pipe (e.g. ≥ 300 mm) may be used to add further storage capacity to a [[bioretention]] or a [[bioswale]] project. Ultimately this idea may result in the use of [[infiltration chambers]] or other void-forming structures to create significant reservoir storage beneath a bioretention filter media bed or permeable pavement. Be sure to check with manufacturers about the compatibility of their systems with trees.

In some cases where the underdrain layer has sufficient depth to accommodate it, a larger diameter perforated pipe (e.g. ≥ 300 mm) may be used to add further storage capacity to a [[bioretention]] or a [[bioswale]] project. Ultimately this idea may result in the use of [[infiltration chambers]] or other void-forming structures to create significant reservoir storage beneath a bioretention filter media bed or permeable pavement. Be sure to check with manufacturers about the compatibility of their systems with trees.

==Underdrains for non-infiltrating practices==

==Underdrains for non-infiltrating practices==