PURPOSE

This section of the guidebook sets forth design criteria for stormwater management systems in accordance with the objectives of managing both the quantity and quality of stormwater runoff.

Whereas basin design for flood control is concerned with capturing and detaining severe runoff events, designs for water quality require that more frequent storm events must be addressed as well. By capturing and treating the frequent storm event, pollutants such as metals, fertilizers, pesticides, oil and grease can be removed from stormwater before it flows offsite or enters the groundwater. To manage both quantity and quality, basins will be designed to capture and treat both the 25-year, 24 hour storm event (see Appendix A) and the first flush volume.