Median pollutant removal percentages for BMPs
Median pollutant removal percentages for several stormwater BMPs. Sources. More detailed information and ranges of values can be found in other locations in this manual, as indicated in the table.
Link to this table
| Practice | TSS | TP | PP | DP | TN | Metals1 | Bacteria | Hydrocarbons |
|---|---|---|---|---|---|---|---|---|
| Infiltration2 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 |
| Biofiltration and Tree trench/tree box with underdrain | 80 | link to table | link to table | link to table | 50 | 35 | 95 | 80 |
| Sand filter | 85 | 50 | 85 | 0 | 35 | 50 | 80 | 80 |
| Iron enhanced sand filter | 85 | 74 | 85 | 606 | 35 | 50 | 80 | 80 |
| Dry swale | 68 | link to table | link to table | link to table | 35 | 0 | 80 | 80 |
| Wet swale | 35 | 0 | 0 | 0 | 0 | |||
| Constructed wet ponds4, 5 | 84 | 46 | 84 | 0 | 30 | 70 | 60 | 80 |
| Constructed wetlands | 73 | 38 | 69 | 0 | 30 | 70 | 60 | 80 |
| Permeable pavement | 74 | 41 | 82 | 0 | ||||
| Green roofs | 85 | 0 | 0 | 0 |
TSS=Total suspended solids, TP=Total phosphorus, PP=Particulate phosphorus, DP=Dissolved phosphorus, TN=Total nitrogen
1Data for metals is based on the average of data for zinc and copper
2BMPs designed to infiltrate stormwater runoff, such as infiltration basin/trench, bioinfiltration, permeable pavement with no underdrain, tree trenches with no underdrain, and BMPs with raised underdrains.
3Pollutant removal is 100 percent for the volume infiltrated, 0 for water bypassing the BMP. For filtered water, see values for other BMPs in the table.
4Dry ponds do not receive credit for volume or pollutant removal
5Removal is for Design Level 2
6Removal is for Tier 2 iron enhanced sand filter. Tier 1 removal is 40 percent, resulting in a TP removal of 65%