1. On-Site Storage Control zRooftop storage zParking lot storage zUnderground storage Commercial developments may have a percentage of impervious areas of 85% or more. On-site storage is often preferred to centralized storage for cost sharing, quality control and spill control. Methods include:-

2. Roof structures 1 2 3 Parking 95% impervious Roads 90% impervious Building footprint 30% Parking and Roads 65% Pervious 5% Total Width W Roof storage 75%total roof area Total Breadth B Parking 67% B Roads 33% B Schematic of Commercial Site

3. Roof structures 1 2 3 Parking 95% impervious Roads 90% impervious Building footprint 30% Parking and Roads 65% Pervious 5% Total Width W Roof storage 75%total roof area Total Breadth B Parking 67% B Roads 33% B Schematic of Commercial Site

4. Example of On Site control Total area 10 ha Imperv. 90% 1.95 Pervious 10% 0.22 Parking 4.33 Roads 2.17 Roof 3.00 Parking & roads 6.50 Grass 0.50 73% imperv 0.50 Imperv. 95% 4.11 Pervious 5% 0.22 Part 3 pervious area Part 3 impervious area 0.72 132 Part 3 total area2.67 1.95

5. Example of On Site control

6. Model Rooftop storage Roof area hectares Store area hectares Area/drain sq.metre Drain flow L/min/25mm Roof slope gH:1V 3.0002.250450.024.000200.00

7. Outflow from Rooftop

8. Parking Lot storage 99.0 100.0Inlet Control Device 100.5

9. Define Wedge storage Wedge invert Grade 1 g1H:1V Grade2 g2H:1V Angle subtended Number of wedges 100.0060.00120.0090.0067.00

10. Outflow from Parking storage

11. Parking lot storage (2) Rim elevation Catch basin Invert level Volume Discharge Rim capacity

12. Compare outflow with and without on-site storage 0.889 0.492