What is stormwater runoff?
Stormwater runoff is water from rain or melting snow that “runs off” across the land instead of seeping into the ground. This runoff usually flows into the nearest stream, creek, river, lake or into the open bottomed "sumps" where it can impact our aquifer. The runoff is not treated.
What is polluted runoff?
Stormwater becomes polluted when it picks up contaminants on its way to groundwater or streams. Contaminants like like pesticides, fertilizers, oil and soap – are harmful in any quantity. Others – like sediment from construction, bare soil, or agricultural land, or pet waste, grass clippings and leaves – can harm creeks, rivers and lakes in sufficient quantities.
In addition to rain and snowmelt, various human activities like watering, car washing, and malfunctioning septic systems can also put water onto the land surface. Here, it can also create runoff that carries pollutants to creeks, rivers and lakes.
Polluted runoff generally happens anywhere people use or alter the land. For example, in developed areas, water that falls on hard surfaces like roofs, driveways, parking lots or roads runs off quickly a picks up pollutants as it travels to storm drains.
What causes polluted stormwater runoff?
Polluted stormwater runoff generally happens anywhere people use or alter the land. People going about their daily lives are the number one source of stormwater pollutants. Most people are unaware of how they impact water quality. Some common examples include over fertilizing lawns, excessive pesticide use, not picking up pet waste, using salt or fertilizer to de-ice driveways, letting oil drip out of their vehicles and littering. Developed areas in general, with their increased runoff, concentrated numbers of people and animals, construction and other activities, are a major contributor to stormwater pollution. Other contributors include forest harvesting activities, roadways, and malfunctioning septic systems.
How are stormwater and runoff “managed”?
“Best management practices” is a term used to describe different ways to keep pollutants out of runoff and to slow down high volumes of runoff.
Preventing pollution from entering water is much more affordable than cleaning polluted water! Educating state residents about how to prevent pollution from entering waterways is one best management practice. Laws that require people and businesses involved in earth disturbing activities --like construction and agriculture -- to take steps to prevent erosion are another way to prevent stormwater pollution. There are also laws about litter, cleaning up after pets and dumping oil or other substances into storm drains.
Education and laws are just two best management practice examples. Some BMPs are constructed to protect a certain area. Some are designed to slow down stormwater, others help reduce the pollutants already in it – there are also BMPs that do both of these things.
Detention ponds, built to temporarily hold water so it seeps away slowly, fill up quickly after a rainstorm and allow solids like sediment and litter to settle at the pond bottom. Then, they release the water slowly. These ponds are one constructed BMP example. Green roofs, storm drain grates, filter strips, sediment fences and permeable paving are other examples.