Stormwater runoff is the greatest threat to water quality today. According to the U.S. Environmental Protection Agency (EPA), 40% of U.S. waterbodies do not meet water quality standards, and the leading source of water quality impairment is polluted stormwater runoff.
Stormwater runoff is rainwater and snowmelt that does not infiltrate into the ground (because it lands on built or paved surfaces), but rather moves over the ground toward a lower elevation and into streams or other receiving waters.
Under natural conditions, most rainwater seeps into the ground and is naturally filtered as it recharges ground water supplies. Impervious surfaces, such as roads, parking lots and rooftops, prevent natural infiltration and thereby increase stormwater flow over land.
Sprawling construction of buildings, roads, parking lots and other impervious surfaces generate increased stormwater runoff. As runoff volumes and velocities increase from new construction, water quality problems such as habitat alteration, damage to aquatic plant and animal populations, sedimentation and increased water temperatures become more pronounced.
Riverkeeper Report: Pave It…Or Save It, Vol. 1 (PDF, 1.5 MB)
Water quality in heavily developed areas degrades with each new development project. By replacing natural soils and wetlands with paved surfaces, the landscape loses its ability to purify stormwater naturally. Rain collects on impervious surfaces, scours pollutants off roads, gathers velocity, and runs off into the nearest surface waters, which are part of our unfiltered drinking water supply.
During periods of heavy rainfall, the combined sewage and stormwater volume can quickly exceed a sewage treatment plant’s capacity in older municipal systems where stormwater and wastewater are combined. In order to keep sewage from backing up in the system – where it could spurt through manhole covers or backflood into homes and businesses, the combined sewer system is designed to overflow during rains and discharge excess wastewater directly into local waterbodies.
The U.S. Environmental Protection Agency (EPA) regulates stormwater through the National Pollutant Discharge Elimination System (NPDES) permit program.
To implement the federal law, New York regulates stormwater as part of the State Pollutant Discharge Elimination System (SPDES) permit program.