Flow through media

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Practices which infiltrate surface runoff through an engineered soil or filter media, and discharge through an underdrain include stormwater planters and some forms of bioretention. The maximum flow rate from the BMP may be limited by the hydraulic conductivity of the mmedium, or by the properties of the perforated pipe.

The maximum flow rate through a bed of filer media (Qmax) may be calculated:

Where:

  • Km is the hydraulic conductivity of the filter media (mm/hr),
  • Ap is the area of the practice (m2),
  • dp is the depth of ponding (mm),
  • dm is the depth of the filter media (mm), and