Cheaper, Faster, Better

Is that enough reason to consider point-source stormwater management? Fayette County Georgia is considering a tax (they call it a fee) for impervious surfaces.

http://www.thecitizen.com/articles/01-21-2014/fayette-seeks-route-stormwater-loan

How about instead of a fee, they offer an incentive, or at least a reduction in the fee, for storing the water and using it? As you'll see in the slides of the Stormwater Management presentation, they offer incentives for residences to put in rain barrels. Why not do the same for commercial buildings? Cost per gallon for commercial is lower than residential. And each project will have a bigger impact.

http://www.fayettecountyga.gov/environmental_management/pdf/Stormwater-Management-Overview.pdf

Another important consideration for stormwater management is how the tank is used. If you want to use the water, i.e. rainwater harvesting, then ideally you keep the tank full.  If your purpose is stormwater management, then the tank needs to be empty before the next rainfall. There is a simple way to do this, and an even simpler way.

Simple Way

Equipment Needed - Tank, Piping, Float Switch, Timer, Pump, Irrigation System

Control Sequence - When the float switch detects water in the tank, wait 48 hours. Then, irrigate until the tank is empty.  It's rain to get a major rain event 2 days in a row. This allows the ground to dry out from the rain, so that it can absorb more water.

You get the added benefit of more water for the plants. You'll also need to mow more often, if you are watering grass. Much better idea would be to water vegetables.

Even Simpler Way

Equipment Needed - Tank. Optional: Piping.

Control Sequence - Drill a hole in the tank, or put an orifice plate in the outlet piping. Calculate the hole size to drain the tank in a day or two. Make a note on your calendar to check the hole for clogs every 6-12 months.