NetSTORM includes three features to facilitate sizing of storage – treatment facilities based upon the STORM method. The program can:

• run repeated simulations to compute results for a range of treatment and runoff rates;
• solve for a user-selected capture efficiency or overflow frequency; or 
• solve for an optimum facility size based upon a method developed by Guo, Urbonas and Tucker (1989) and formerly incorporated into Sacramento’s drainage regulations (Sato and Associates, 1991; City and County of Sacramento, 1996)

 

In the repeated simulations approach, the user selects an initial storage volume and treatment rate, as well as treatment rate and storage volume multipliers. The program then runs multiple STORM analyses and reports overflows per year and percent capture for each iteration. The program iterates until 100 percent capture is achieved or a user-selected maximum number of simulations is performed.

 

When the program solves for user-selected capture efficiency or overflow frequency, the program runs repeatedly using a linear search algorithm to satisfy the target condition.

 

The optimum facility size method in NetSTORM examines the response surface of capture efficiency versus storage volume based on a fixed time-to-empty (also termed drawdown time) where storage volume is normalized to the storage volume needed to achieve 99.9% capture efficiency. The program solves for the point on the response curve with a slope of one, where capture efficiency increases at the same rate as normalized storage volume.