Realistic Infiltration Rates for Specified Soil Mixtures

[Riversidean]

Currently I am working on getting the drawdown for my bioretention basins below three days. The controlling factor seems to be the infiltration rate of whatever soil mixture I use. Now realistically I know the best soil type I may ever get is 5 to 6 inches, but this won't allow me to drain the entire bioretention bmp volume within the 3 days required. Does anyone know if infiltration rates of 12 - 15 inches per hour is realistic? Do these infiltration rates possibly account for evaporation and evapotranspiration from plants inside the bioretention basins?

Any help would be appreciated.

 

[TerryScan]

It sounds like the facility is not sized large enough. In my locale, the required soil mix has a rate of 2.83in/hr as tested by the regulating agency. I suspect a mix that has a rate of 12-15in/hr would not be providing the desired filtering.