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Line 15:
Line 15: *''R'' = ''A<sub>i</sub>''/''A<sub>p</sub>''; the ratio of impervious contributing drainage area (''A<sub>i</sub>'') to permeable pavement area (''A<sub>p</sub>''). Note that the contributing drainage area should not contain pervious areas. R should not exceed 2.
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*''A<sub>i</sub> = Impervious contributing drainage area (m<sup>2</sup>)
*''A<sub>i</sub> = Impervious contributing drainage area (m<sup>2</sup>)
*''A<sub>p</sub> = Permeable pavement area (m<sup>2</sup>)
*''A<sub>p</sub> = Permeable pavement area (m<sup>2</sup>)
*''f''' = [[Design infiltration rate]] of underlying native soil (m/hr)
*''f''' = [[Design infiltration rate]] of underlying native soil (m/hr)
*''n'' = Porosity of the stone bed aggregate material (typically 0.4 for 50 mm dia. [[reservoir aggregate|clear stone]])}}
*''n'' = Porosity of the stone bed aggregate material (typically 0.4 for 50 mm dia. [[reservoir aggregate|clear stone]])}}
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It is important to note that ''R'' = ''A<sub>i</sub>''/''A<sub>p</sub>''; the ratio of impervious contributing drainage area (''A<sub>i</sub>'') to permeable pavement area (''A<sub>p</sub>'') should not exceed 2 and that the contributing drainage area should not contain pervious areas that are sources of sediment that can lead to premature clogging.
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On highly permeable soils (e.g., infiltration rate of 45 mm/hr or greater), a maximum stone reservoir depth of 2 metres is recommended to prevent soil compaction and loss of permeability from the mass of overlying stone and stored water.
On highly permeable soils (e.g., infiltration rate of 45 mm/hr or greater), a maximum stone reservoir depth of 2 metres is recommended to prevent soil compaction and loss of permeability from the mass of overlying stone and stored water.