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| |Filter media Plant-Available Phosphorus > 40 ppm||Filter media Plant-Available Phosphorus < 40 ppm | | |Filter media Plant-Available Phosphorus > 40 ppm||Filter media Plant-Available Phosphorus < 40 ppm |
| |- | | |- |
− | |Filter media predominantly sand||Filter media contains fractions of fines and organic material in sand | + | |Filter media is predominantly sand||Filter media is a mixture of sand, topsoil and organic material |
| |- | | |- |
− | |Surface covered with stone (or uncovered)||Surface covered with mulch and dense vegetation | + | |Surface covered with turf grass and stone||Surface covered with mulch and dense, deeply rooting vegetation |
| |} | | |} |
| | | |
| ===Sizing and Modelling=== | | ===Sizing and Modelling=== |
− | Bioretention facilities should be sized to accommodate runoff from approximately 10 to 20 times the footprint area of the facility. i.e. they should have an I/P ratio of 10 to 20. | + | Bioretention facilities should be sized to accommodate runoff from approximately 5 to 20 times the footprint area of the facility. i.e. they should have an I/P ratio of 5 to 20. |
| When the drainage area is too large, silt can accumulate very rapidly, overwhelm the [[pretreatment]] devices, and lead to clogging of the facility. | | When the drainage area is too large, silt can accumulate very rapidly, overwhelm the [[pretreatment]] devices, and lead to clogging of the facility. |
− | When the drainage area is relatively small compared to a bioretention facility, it can make the facility appear unreasonably costly. | + | When the drainage area is relatively small compared to a bioretention facility, it can make the facility unreasonably costly. |
| *'''[[Bioretention: Sizing| Sizing]]''' | | *'''[[Bioretention: Sizing| Sizing]]''' |
| *'''[[Bioretention: TTT| Modelling]]''' | | *'''[[Bioretention: TTT| Modelling]]''' |
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| *A [[gravel diaphragm]] for sheet flow | | *A [[gravel diaphragm]] for sheet flow |
| *[[Vegetated filter strips]] for sheet flow | | *[[Vegetated filter strips]] for sheet flow |
− | *A [[Forebays|forebay]] for concentrated overground flow | + | *A [[Forebays|forebay]] for concentrated surface flow |
| *An [[Oil and grit separators|oil and grit separator]] for concentrated underground flow | | *An [[Oil and grit separators|oil and grit separator]] for concentrated underground flow |
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