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Line 68: [[File:PermeablePaving CrossSection.png|thumb|550px|Permeable Pavement cross sections showing full and partial infiltration designs. Source: GVRD, 2005]]
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[[File:OverflowEdge.png|thumb|Porous asphalt system with overflow edge draining to a reservoir. Source: Pennsylvania Department of Environmental Protection (PDEP). 2006.]]
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→Design
==Design==
==Design==
[[File:PermeablePaving CrossSection.png|thumb|550px|Permeable Pavement cross sections showing full and partial infiltration designs. Source: GVRD, 2005]]
===Subgrade===
===Subgrade===
For infiltrating pavements, subgrade slopes should be minimized so that runoff will be able to infiltrate evenly through the entire surface. For steeply sloped sites (>5%), check dams, berms or weir structures on the native soils of the pavement should be considered. If the system is not designed for infiltration, the bottom should be sloped at 1 to 5% toward the underdrain. Subgrades should be compacted to 95% Standard Proctor Density. If a lesser value is desired to promote infiltration, a thicker sub-base should be considered. Subgrade soils should not be scarified.
For infiltrating pavements, subgrade slopes should be minimized so that runoff will be able to infiltrate evenly through the entire surface. For steeply sloped sites (>5%), check dams, berms or weir structures on the native soils of the pavement should be considered. If the system is not designed for infiltration, the bottom should be sloped at 1 to 5% toward the underdrain. Subgrades should be compacted to 95% Standard Proctor Density. If a lesser value is desired to promote infiltration, a thicker sub-base should be considered. Subgrade soils should not be scarified.
===Underdrain===
===Underdrain===
The diagram below displays permeable pavement cross sections showing full and partial infiltration designs.<ref>Greater Vancouver Regional District (GVRD). 2005. Stormwater Source Control Design Guidelines 2005. Prepared by Lanarc Consultants Limited, Kerr Wood Leidal Associates Limited and Goya Ngan. </ref> See [[Underdrains]] page for further guidance.
The diagram below displays permeable pavement cross sections showing full and partial infiltration designs.<ref>Greater Vancouver Regional District (GVRD). 2005. Stormwater Source Control Design Guidelines 2005. Prepared by Lanarc Consultants Limited, Kerr Wood Leidal Associates Limited and Goya Ngan. </ref> See [[Underdrains]] page for further guidance.
===Access Structures===
===Access Structures===
===Overflow===
===Overflow===
All designs require an overflow outlet connected to a storm sewer with capacity to convey larger storms. This is normally achieved with a catch basin outlet, but water may also be directed to a downstream practice (e.g. bioretention, swale). Another option is a gravel diaphragm or trench along the downgradient edge of the pavement that drains to the storage reservoir below.
All designs require an overflow outlet connected to a storm sewer with capacity to convey larger storms. This is normally achieved with a catch basin outlet, but water may also be directed to a downstream practice (e.g. bioretention, swale). Another option is a gravel diaphragm or trench along the downgradient edge of the pavement that drains to the storage reservoir below.
===Foundation Aggregates===
===Foundation Aggregates===
[[File:OverflowEdge.png|thumb|Porous asphalt system with overflow edge draining to a reservoir. Source: Pennsylvania Department of Environmental Protection (PDEP). 2006.]]
All aggregates should meet the following criteria:
All aggregates should meet the following criteria:
* Porosity of 0.4
* Porosity of 0.4
For more information, also see [[Aggregates]] page.
For more information, also see [[Aggregates]] page.
===Sizing Stone Reservoirs===
===Sizing Stone Reservoirs===