Void Ratios for stormwater retention facilities
Void Ratios for stormwater retention facilities
(OP)
I've proposed a bioretention area for a project which is sized based on the runoff volume. This is in California and is based on the C3 Technical Guidance Manual. I used a void ratio for biotreatment soil and for Caltrans class 2 permeable material of 0.35. However, the County Planning Dept reviewer said the void ratio for both is 0.01 to 0.05, which is ridiculously low. I tried to find void ratios for both of these materials on line, but could find nothing. Does anyone know of a reliable data source for these two materials?
RE: Void Ratios for stormwater retention facilities
Peter Smart
HydroCAD Software
www.hydrocad.net
RE: Void Ratios for stormwater retention facilities
Mike McCann, PE, SE (WA)
RE: Void Ratios for stormwater retention facilities
"Void ratio" is the ratio of voids to solids, so 25% porosity would be a void ratio of 25:75 or 1:3
Peter Smart
HydroCAD Software
www.hydrocad.net
RE: Void Ratios for stormwater retention facilities
RE: Void Ratios for stormwater retention facilities
Mike McCann, PE, SE (WA)
RE: Void Ratios for stormwater retention facilities
V1 is the floodable volume above the soil layer (that is, the total volume of surface storage when the facility just begins to overflow). V2 is the storage volume below the soil layer. If gravel fill is used, multiply the volume of gravel by an assumed porosity of 0.4 to obtain the subsurface volume.