The secondary storm water system consists of all the minor drainage and storm sewers that collect and transport storm water to the primary system. According to the BCS Unified Storm water Design Guidelines, evaluation of the 2-year, 10-year, 25-year, 50-year, and 100-year design storms are used to reach the maximum design storm. The resulting maximum design storm is then used for detention facility calculations. In addition, the 100-year design storm needs to be evaluated for the effects of resulting flows on downstream drainage systems.
