Stormwater Infiltration

[JonathanSteven]

Two Questions..

1) Is there a reccomended rate or range of rates of infiltration when using structural fill?

2) Are allowable/acceptable infiltration rates for recharge governed by local ordinances or the BMP Manual? Site is in PA

Thanks!

 

[psmart]

Since you mention "structural fill", I'm guessing this is an underground chamber system.

The infiltration rate will depend on the surrounding (native) soil, and not on the structural fill. There are no "recommended" rates. It all depends on the soil and groundwater conditions of the particular site.


Peter Smart
HydroCAD Software

http://www.hydrocad.net

 

[JonathanSteven]

The existing profile consists of uncontrolled fill overlying natural soils. We performed infiltration testing on the natural soils, but unfortunately they lie below seasonal high groundwater elevations. Our reccomendation was be to overexcavate the uncontrolled fill and "build" a basin consisting of a 2' or more thick layer of structural fill.

 

[psmart]

The stone storage is typically modeled as a "pond", with the voids providing the storage. In this scenario, the water is assumed to flow freely within the stone and form a level pool. As such, the infiltration rate of the stone itself usually doesn't enter into the calculation.

Of course, if your inflow is so high that a level-pool will not form, you would need to perform a more complex mounding analysis within the stone itself. But if your flow is that high, stone storage may not be adequate for your site.




Peter Smart
HydroCAD Software

http://www.hydrocad.net