Pollutants in stormwater runoff
Increased Runoff
Land alterations increases the rate and amount of runoff from the watershed entering the
stream.
Carries pollutants, erodes stream channel and banks, and destroys instream habitat
Dirt and sand on roads, driveways, and parking lots or eroded sediment from disturbed
surfaces (e.g. construction sites) enters stream with stormwater runoff; increased flow
causes stream bank erosion
Smothers aquatic habitat, depletes oxygen, reduces water clarity, and carries nutrients and toxic contaminants
Excess fertilizers on lawns or fields, failing septic systems, and animal waste
Stimulates excessive plant growth, lowers dissolved oxygen levels, degrades aesthetics and destroys native aquatic life
Temperature
Warmer water caused by runoff from impervious surfaces, removal of streamside
vegetation, and reduction in groundwater flows
Harmful to trout and other cold water species, promotes spread of invasive species and excessive plant growth, reduces dissolved oxygen levels in water
Potentially pathogenic microscopic organisms in failing septic systems, sewer overflows,
and animal (including pet) waste
Harmful to humans; untreated waste can cause numerous diseases.
Toxic Contaminants/Heavy Metals
Heavy metals such as Mercury, cleaning compounds, pesticides and herbicides, industrial
by-products such as dioxin, and vehicle leakage of oil, gas, etc.
Harmful to humans and aquatic life at fairly low levels; many resist breakdown and some accumulate in fish and other animal tissues (including human), and can lead to mutations, disease, or cancer