The equation for the depth of the stone reservoir (''d<sub>r, max</sub>'', mm) is as follows:
The equation for the depth of the stone reservoir (''d<sub>r, max</sub>'', mm) is as follows:
−
<math>d_{r, max}=\frac{\left[\left ( RVC_{T}\times R \right )+ RVC_{T}-\left(f'\times t\right )\right]}{n}</math>
+
<math>d_{r, max}=\frac{\left[\left ( RVC_{T}\times R \right )+ RVC_{T}-\left(f'\times D\right )\right]}{n}</math>
{{Plainlist|1=Where:
{{Plainlist|1=Where:
*''RVC<sub>T</sub>'' = [[Runoff volume control target]] (mm)
*''RVC<sub>T</sub>'' = [[Runoff volume control target]] (mm)
*''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 normally exceed 2.
*''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 normally exceed 2.
*''f''' = [[Design infiltration rate]] of underlying native soil (mm/hr)
*''f''' = [[Design infiltration rate]] of underlying native soil (mm/hr)
−
*''t'' = Duration of the design storm event (e.g., 2 hr)
+
*''D'' = Duration of the design storm event (e.g., 2 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]])}}