Infiltration TrenchDesign Notes Cont’d

• Surface area of trench is determined by:

At = Vw / (ndt + fT)

Where:

At = surface area of trench

Vw = design volume entering trench (e.g., WQv)

n = porosity

dt = trench depth based on the depth required above seasonal groundwater table or a depth less than dmax, whichever is smaller

f = infiltration rate of trench

T = time to fill trench (generally assumed to be less than 2 hours)

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Trench surface area is determined by the above equation.