Infiltration: TTT
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| Surface | |
|---|---|
| Berm height (mm) | This is the height of the curb which constrains the overland sheet flow of water. Where curb cuts or other outlet exists at the lowest point of an infiltration surface, the suggested value is 0. |
| Surface roughness (Manning’s n) | Lower numbers indicate less surface obstruction and result in faster flow. Suggested range for a surface of decorative rocks 0.03 – 0.05 [1] |
| Surface slope (%) | If the slope > 3%, consider using Checkdams or weirs to prevent erosion of the surface under high flow velocities. |
| Storage | |
| Thickness (mm) | Entire trench |
| Void ratio | Suggest range 0.35 – 0.4 (unless otherwise tested) for designs using just aggregates for storage. For any design using preformed infiltration chambers, the overall ‘effective void ratio’ will vary according to product geometry. Contact manufacturer(s) for recommended value. |
| Seepage rate (mm/hr) | Infiltration rate of native soil |
| Clogging factor | ? |
| Design drawdown time (hrs) | Recommend 48 hours? |
| Drain (underdrain) | |
| Flow coefficient | Suggested value 1 |
| Flow exponent | Suggested value 1 |
| Offset height | This is the height from the base of the cell to the height at which the drain discharges. In some designs this may be the height of the perforated pipe within the storage layer. In other designs this height is adjusted by creating an upturn in the discharge pipe. |
- ↑ Oregon State Univ., Corvallis. Dept. of Civil, Construction and Environmental Engineering.; Environmental Protection Agency, Cincinnati ONRMRL. Storm Water Management Model Reference Manual Volume I Hydrology (Revised). 2016:233. https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=P100NYRA.txt Accessed August 23, 2017.