Stormwater Runoff
What is stormwater runoff?
Where does stormwater come from?
What are the some stormwater pollutants and sources?
What are the impacts of stormwater runoff?
Does stormwater impact our New York City drinking water?
What are impervious surfaces?
What are the stormwater regulations?
What are SPDES permits?
What is an MS4?
What’s Phase I?
What’s Phase II?
What is required under Phase II?
What is a Best Management Practice (BMP)?
Why Stormwater Matters
What is stormwater runoff?
Stormwater is water that flows across the ground or pavement when it rains or when snow or ice melt. The water seeps into the ground or drains into storm sewers, which can be seen at street corners or low points on the sides of the streets. Collectively, the draining water is called stormwater runoff.
Where does stormwater come from?
It doesn't come from a single source such as pollution from industrial and sewage treatment plants, yet, is more damaging to fish, wildlife and habitat as well as to drinking water supplies. When left uncontrolled these discharges can result in fish kills, the destruction of spawning and wildlife habitats, a loss in aesthetic value and contamination of drinking water supplies and recreational waterways that threatens public health.
What are the some stormwater pollutants and sources?
Sediment: Often originating as topsoil, sand, and clay, it is the most common pollutant in stormwater runoff by volume and weight. Sediments readily wash off paved surfaces and exposed earth during storms. Sediment may seem harmless enough, but it poses serious problems in the water. Excess sediment can turn water cloudy thereby making it less suitable for recreation, fish life, and plant growth; clog storm drains, leading to increased private and public maintenance costs and flooding problems. It also poses a health risk since when sediments enter water they usually carry other pollutants including oils, metals, bacteria, and nutrients with them.
Sources: Cleared construction sites and exposed earth are generally the greatest contributors of soil particles in surface waters. Other sources include erosion from agricultural lands, application of sand and salts to icy roads, fallout from pressure washing and sandblasting operations, dirt from equipment and vehicles, and dirt and grit from parking lots, driveways, and sidewalks.
Oils and Greases: Oils and greases are a common component of stormwater runoff pollutants, primarily because there are so many common sources: streets and highways, parking lots, food waste storage areas, heavy equipment and machinery storage areas, and areas where pesticides have been applied. The familiar sight of a rainbow-colored puddle or trickling stream in parking lots, driveways, and street gutters is a reminder of the presence of oils and greases in stormwater runoff. No type of oil or grease belongs in surface water. Sources: Oils and greases can be petroleum-based (such as motor oil) or food-related (such as cooking oils).
Heavy metals: Lead, copper, zinc and cadmium, are commonly found in urban runoff. Metals can contaminate surface and ground waters and concentrate in bottom sediments, presenting health problems for fish and animals that eat from the bottom. Reproductive cycles of bottom-dwelling species can be severely reduced, and fish inhabiting such metal-contaminated locations often exhibit lesions and tumors. Metals can also contaminate drinking water supplies.
Sources: Industrial areas, scrap yards, paints, pesticides, and fallout from automobile emissions.
Oxygen-Demanding Substances: Plant debris, food waste, and some chemical wastes fall into a category of water pollutants known as oxygen demanding substances. Such substances use dissolved oxygen in water when they decay or chemically react: if dissolved oxygen levels in water become too low, aquatic animals can become stressed or die.
Sources: Animal wastes, food wastes, leaves and twigs, and other miscellaneous organic matter.
Nutrients: Nutrients such as phosphorus and nitrogen are needed by plants to grow, but high levels can be harmful to water quality. Excess nutrient levels can over-stimulate the growth of algae and other aquatic plants, resulting in unpleasant odors, unsightly surface scums, and lowered dissolved oxygen levels from plant decay.
Sources: Pet, bird and other animal wastes, failing septic systems, fertilizers, detergents, road deicing salts, automobile emissions, and organic matter such as lawn clippings and leaves.
Toxic Organic Compounds: Pesticides and PCBs are toxic organic compounds that are particularly dangerous in the aquatic environment. Excessive application of insecticides, herbicides, fungicides, and rodenticides, or application of any of these shortly before a storm, can result in toxic pesticide chemicals being carried from agricultural lands, construction sites, parks, golf courses, and residential lawns to receiving waters.
Sources: wood preservatives, antifreeze, brake fluid, gasoline, paint thinners, pesticides, fertilizers, furniture strippers, dry cleaning chemicals, cleansers, solvents and a variety of other chemical products.
Litter: Litter improperly disposed of, including bottles and cans, paper and plastic bags, fast-food wrappers, cigarette butts and more pose a danger to water quality.
Sources: All of us
What are the impacts of stormwater runoff?
Where it falls on impervious surfaces, stormwater can run off toward waterways with such force and volume that it can cause severe stream degradation by eroding stream banks like a bulldozer. Stormwater runoff can lead to increased sedimentation and flooding.
Does stormwater impact our New York City drinking water?
Stormwater runoff is the largest source of pollutants in the New York City watershed and the prime reason why most of our drinking water reservoirs are phosphorous impaired; 84% of the phosphorous in our streams and reservoirs is from non-point sources, including stormwater.
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