Water Quality Treatment Volume (WQv)Options
Where A = area in acres, P = 90% rainfall event in inches, Rv = volumetric runoff coefficient,
P2 = annual average precipitation
Notes:
Several options are available for establishing a water quality criteria. In this presentation, we focus on the 90% rule as the recommended treatment option because it treats the majority of the total average annual volume of runoff and is a function of impervious cover, thereby providing an incentive to reduce the total imperviousness of a site.