The first flush is the initial runoff from a storm and tends to carry a higher concentration of pollutants compared to later in the storm. Common contaminants picked up in the first flush include:
– sediment from roofs
– yardwaste, animal waste, fertilizers, pesticides and de-icing compounds from driveways and yards
– brake dust, tire residue, heavy metal and trash from street surfaces
Simple ways to reduce the concentration of pollutants in the first flush include using lawn chemicals as directed, biking or walking more and creating landscapes that promote natural infiltration.
Graphic courtesy of cleanwatercampaign.org