Design-Storm Runoff Volume & SG Module Pre-Sizer

A first-pass estimate of the runoff your site sheds in a design storm, and how many SG modules would hold it — before the release-rate routing that sets true detention storage.

1. Impervious area draining to the tank

Roofs, drives and paving, in square feet (ft²).

2. Design storm rainfall depth

In inches — your jurisdiction’s design event (e.g. the local 10-year or 100-year 24-hour depth from NOAA Atlas 14).

3. Runoff coefficient (C)

4. SG module

Both cell heights carry the same ~95% void ratio.

Enter your figures and press Estimate.