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<math>{I_z \over I_0}= e^{-kz}</math>ΔT50 = Time to drain last 50 mm of surface ponded waterΔT50 = (T2 – T1)*24T1 = Post-storm date and time (mm/dd/yyyy hh:mm:ss) when surface ponding water level reaches T2 = Post-storm date and time (mm/dd/yyyy hh:mm:ss) when surface ponding is fully drained
→Calculation
====Calculation====
====Calculation====
Filter Bed Surface Infiltration Rate <math>i = 50mm \frac Δ_T50}</math><br>
Filter Bed Surface Infiltration Rate <math>i= {50mm \over Δ_T50}</math>
Where<br>
Where;
''ΔT<sub>50</sub>'' = Time to drain last 50 mm of surface ponded water<br>
''ΔT<sub>50</sub>'' = (''T<sub>2</sub>'' – ''T<sub>1</sub>'') x ''24''<br>
''T<sub>1</sub>'' = Post-storm date and time (mm/dd/yyyy hh:mm:ss) when surface ponding water level reaches ''50 mm in depth''.<br>
''T<sub>2</sub>'' = Post-storm date and time (mm/dd/yyyy hh:mm:ss) when surface ponding is fully drained<br>
50 mm in depth.
<math>d_{r} = \frac{f'\times t}{n} </math>
Where <br>
''f''' = [[design infiltration rate]] of the native soil (m/h) <br>
''t'' = [[drainage time]], based on local criteria or long-term average inter-event period for the location (e.g. 72 hr in southern Ontario).<br>
''n'' = Porosity of the stone bed aggregate material (typically 0.4 for 50 mm dia. [[reservoir aggregate|clear stone]])
<br>
==Natural or Simulated Storm Event Testing==
==Natural or Simulated Storm Event Testing==