Changes

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:   

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.

* Native soils have high infiltration capacity.

* Impervious surface draining onto the permeable pavement is limited or absent.

* Impervious surfaces draining onto the permeable pavement surface is limited or absent.

* Underdrain is elevated above the native soil and/or a flow restrictor is installed on the underdrain.

* Underdrain is elevated above the native soil and/or a flow restrictor is installed on the underdrain or outlet storm sewer pipe.

All permeable pavements have very high surface infiltration rates when appropriately maintained.  Therefore, the surface course type (e.g. permeable interlocking concrete pavers, pervious concrete, porous asphalt, etc.) is not a key factor in determining volumetric runoff reduction performance.  

All permeable pavements have very high surface infiltration rates when appropriately constructed and maintained.  Therefore, the surface course type (e.g. permeable interlocking concrete pavers, pervious concrete, porous asphalt, etc.) is not a key factor in determining volumetric runoff reduction performance.  

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