The equation for the depth of the stone foundation (''d<sub>f, max</sub>'', mm) is as follows:
The equation for the depth of the stone foundation (''d<sub>f, max</sub>'', mm) is as follows:
−
<math>d_{f, max}=\frac{\left[\left ( Q_c\times R \right )+ P-\left(f'\times t\right )\right]}{V_{R}}</math>
+
<math>d_{f, max}=\frac{\left[\left ( RVC_{T}\times R \right )+ RVC_{T}-\left(f'\times t\right )\right]}{V_{R}}</math>
{{Plainlist|1=Where:
{{Plainlist|1=Where:
−
*''Q<sub>c</sub>'' = Depth of runoff from contributing drainage area, not including permeable paving surface (mm)
+
*''RVC<sub>T</sub>'' = Depth of runoff from contributing drainage area, not including permeable paving surface (mm)
*''R'' = ''A<sub>c</sub>''/''A<sub>p</sub>''; the ratio of contributing drainage area (''A<sub>c</sub>'') to permeable paving area (''A<sub>p</sub>''). Note that the contributing drainage area (''A<sub>c</sub>'') should not contain pervious areas. R should not normally exceed 2.
*''R'' = ''A<sub>c</sub>''/''A<sub>p</sub>''; the ratio of contributing drainage area (''A<sub>c</sub>'') to permeable paving area (''A<sub>p</sub>''). Note that the contributing drainage area (''A<sub>c</sub>'') should not contain pervious areas. R should not normally exceed 2.