Slide 8 of 100
Notes:
Stormwater ponds have some of the best water quality performance capabilities of any stormwater treatment practice. This is in large part due to the residence time and settling properties of the permanent pool.
Several studies have documented that the majority of the annual pollutant load associated with stormwater runoff is associated with the smaller more frequent events, and that the smaller sized sediment particles carry most of the pollutant load. Consequently, it is recommended that water quality treatment volumes target the smaller storms and that adequate pretreatment is provided. For many of the humid areas of the country, about 90 percent of all rainfall events are in the range of approximately 1 inch. In the absence of a more rigorous rainfall frequency analysis, 1 inch of rainfall per impervious acre is a reasonable criteria to shoot for.
