Pollutant Concentration in Highway Runoff
In addition to sediment, runoff from roadways can contain heavy metals, oxygen demanding material, and nutrients. There is a strong relationship between the volume of traffic carried on a roadway and the event mean concentration of pollutants in runoff as shown in the table below.
Pollutant Concentration in Highway Runoff (source: Driscoll et al. 1990, Federal Highway Administration)
| Pollutant | EMC* in runoff, <30,000 vehicles per day (mg/l) | EMC* in runoff, >30,000 vehicles per day (mg/l) |
| Total suspended solids | 41 | 142 |
| Volatile suspended solids | 12 | 39 |
| Total organic carbon | 8 | 25 |
| Chemical oxygen demand | 49 | 114 |
| Nitrite and nitrate | 0.46 | 0.76 |
| Total Kjeldahl N | 0.87 | 1.83 |
| Phosphorus | 0.16 | 0.40 |
| Copper | 0.022 | 0.054 |
| Lead | 0.080 | 0.400 |
| Zinc | 0.080 | 0.329 |
*EMC is event mean concentration
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