Feedback post on Infiltration: Sizing and modeling

Equation for "Drawdown time to empty facility" 1) it is not clear in the equation whether the ln, is natural logarithm, or "I" (Impermeable Area i.e. catchment) and "n" (porosity) 2) the graphic with footprint area shows two footprint areas, but the caption states there are three and doesn't have the correct x for the 2nd shape.