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Line 167:
Line 167: − Research on the volumetric runoff reduction performance of permeable pavements have been conducted on pavements with and without an underdrain in the base. Volumetric performance improves when: + − * Native soils have high infiltration capacity. − * Impervious surface draining onto the permeable pavement is limited or absent. − * Underdrain is elevated above the native soil and/or a flow restrictor is installed on the underdrain. − All permeable pavements have very high surface infiltration rates when appropriately maintained. Therefore, the surface course type (i.e. PICP, pervious concrete) is not a key factor in determining volumetric runoff reduction performance. + + + + + − + − + − + Line 210:
Line 211: − +
→Performance
===Water Balance===
===Water Balance===
Bioretention has been shown to reduce runoff volume through evapotranspiration and infiltration of runoff. The research can be classified into bioretention applications that include underdrains and those that do not (and therefore rely on full infiltration into underlying soils). Aside from the underdrain, many other factors can impact the water balance
Aside from the underdrain, many other factors can impact the water balance performance of a bioretention installation:
* Native soil infiltration rate;
* Rainfall patterns; and,
* Various sizing criteria on a per-installation basis.
{|class="wikitable"
{|class="wikitable"
|+Volumetric runoff reduction from permeable pavements
|+Volumetric runoff reduction from Bioretention
|-
|-
!'''LID Practice'''
!'''LID Practice'''
!'''Location'''
!'''Location'''
!'''<u><span title="Note: Runoff reduction estimates are based on differences between runoff volume from the practice and total precipitation over the period of monitoring unless otherwise stated." >Runoff Reduction*</span></u>'''
!'''<u><span title="Note: Runoff reduction estimates are based on differences in runoff volume between the practice and a conventional impervious surface over the period of monitoring." >% Runoff Reduction*</span></u>'''
!'''Reference'''
!'''Reference'''
|-
|-
|rowspan="6" style="text-align: center;" | Permeable pavement without underdrain
|rowspan="6" style="text-align: center;" | Bioretention without underdrain
|style="text-align: center;" |Guelph, Ontario
|style="text-align: center;" |Guelph, Ontario
|style="text-align: center;" |90%
|style="text-align: center;" |90%
|style="text-align: center;" |<span class="plainlinks">[https://sustainabletechnologies.ca/app/uploads/2013/03/PP_FactsheetSept2011-compressed.pdf TRCA (2008)]</span>
|style="text-align: center;" |<span class="plainlinks">[https://sustainabletechnologies.ca/app/uploads/2013/03/PP_FactsheetSept2011-compressed.pdf TRCA (2008)]</span>
|-
|-
|rowspan="10" style="text-align: center;" | Permeable pavement with underdrain
|rowspan="10" style="text-align: center;" | Bioretention with underdrain
|-
|-
|style="text-align: center;" |Vaughan, Ontario
|style="text-align: center;" |Vaughan, Ontario