Stormwater Protection Program

Sediment

• Sediment is often viewed as the largest pollutant load associated with stormwater runoff in an urban setting. The loadings have been shown to be exceptionally high in the case of construction activity.
• Sediment is associated with numerous impacts in surface waters including increased turbidity, effects on aquatic and benthic habitat and reduction in capacity of impoundments.
• A number of other pollutants often attach to, and are carried by, sediment particles.

Nutrients

• The nutrients most often identified in stormwater runoff are phosphorus and nitrogen.
• In surface waters, these nutrient loads can lead to heavy algae growth, eutrophication (especially in impoundments) and low dissolved oxygen levels.
• Nutrients enter the urban system in a variety of ways, including landscaping practices (commercial and home), leaks from sanitary sewers and septic systems, and animal wastes.

Organic Matter

• Various forms of organic matter may be carried by stormwater in urban areas. Decomposition of this material by organisms in surface waters results in depleted oxygen levels.
• Low levels of dissolved oxygen severely impact water quality and life within surface waters.
• Sources of organic matter include leaking septic systems, garbage, yard waste, etc.

Bacteria

• High bacterial levels may be found in stormwater runoff as a result of leaking sanitary systems, garbage, pet waste, etc.
• The impacts of bacteria on surface waters may affect recreational uses and aquatic life as well as impose health risks.

Oil and Grease

• Numerous activities in urban areas produce oil, grease, and lubricating agents that are readily transported by stormwater.
• The intensity of activities, including vehicle traffic, maintenance and fueling activities, leaks and spills, and manufacturing processes within an urban setting contribute heavily to the level of these pollutants present in adjacent surface waters.

Toxic Substances

• Many toxic substances are potentially associated with urban stormwater including metals, pesticides, herbicides and hydrocarbons.
• Toxic compounds may affect biological systems, and accumulate in bottom sediments of surface waters.

Heavy Metals

• Heavy metals such as copper, lead, zinc, arsenic, chromium and cadmium may be typically found in urban stormwater runoff.
• Metals in stormwater may be toxic to some aquatic life and may accumulate in aquatic animals.
• Urban sources of metals in stormwater may include automobiles, paints, preservatives, motor oil and various urban activities.

Temperature

• Stormwater runoff increases in temperature as it flows over impervious surfaces. In addition, water stored in shallow, unshaded ponds and impoundments can increase in temperature.
• Removal of natural vegetation (such as tree canopy) opens up water bodies to direct solar radiation.
• Elevated water temperatures can impact a water body’s ability to support certain fish and aquatic organisms.