BMP selection based on physical feasibility
This table shows guidance on BMP selection based on physical feasibility characteristics of a site.
Link to this table.
| BMP group | Surface areaa | Drainage area | Soil infiltration rate | Head | Separation from bedrock | Depth to seasonally high water table | Maximum slopec | Ultra-urban |
|---|---|---|---|---|---|---|---|---|
| Bioretention | 7-10%; Minimum 200 ft2 b | 5 acre maximum; 0.5-2.0 acre preferred | Any soil; use underdrain for C and D soilsd | 4-6 feet | 3 feet | 3 feet | 20% | Yes |
| Filtration - media | Negligible, except for access | 5 acre maximum; 0.5-2.0 acre preferred | Media part of designd | 2-6 feet | 0 feet if enclosed | 3 feet for vegetated; 0 feet if enclosed | 20% | Yes |
| Filtration - vegetative | Varies based on depth | 10 acre maximum | Media part of design | 2-6 feet | 0 feet if enclosed | 3 feet for vegetated; 0 feet if enclosed | 20% | Possible |
| Infiltration trench | Varies based on depth | 5 to 10 acre maximum | Native soils with i >= 0.2 inches/hour | 2-12 feet | 3 feet | 3 feet | 15% | Possible |
| Infiltration basin | Varies based on depth | 5 to 50 acre maximum | Native soils with i >= 0.2 inches/hour | 2-12 feet | 3 feet | 3 feet | 15% | No |
| Stormwater ponds | 1-3% | 10 to 25 acres recommendedb | A or B soils may require liner | 3-10 feet | 0 feet (shallow soil limits design) | 0 feet (except if hotspot or aquifer) | 25% | No |
| Constructed wetlands | 2-4% | 25 acre minimumb | A or B soils may require liner | 3-10 feet | 0 feet | 0 feet (except if hotspot or aquifer) | 25% | No |
aSurface area as a function of contributing surface area, except for ponds and wetlands, where it is a function of entire drainage area
b10 acres or less may be feasible if groundwater is intercepted and/or if water balance calculations indicate a wet pool can be sustained
cSlope is defined as the slope across the proposed location of the practice
dInfiltration gallery could be designed to provide limited recharge