Click here or scroll to learn more about stormwater pollution, solutions, and more!
What is Stormwater?
When rain, snow, or another type of precipitation hits a surface, it becomes stormwater. In natural landscapes, stormwater gets soaked up into the ground or falls directy into waterbodies. However, when rain or water hit hard surfaces like pavement, sidewalks, and roofs it creates stormwater runoff. On its journey, stormwater picks up and transports many of the pollutants it encounters, which are NOT treated before draining directly to the rivers, streams, and lakes that hold our drinking water. These pollutants include sediment, pet wastes, pesticides, fertilizers, automobile fluids (such as oil, gasoline, and antifreeze), yard wastes, cigarette butts, litter, and more. By carrying all these different kinds of pollution into our waterways, stormwater runoff itself becomes a pollutant!
In addition to stormwater pollutants, stormwater quantity can also become an issue when too much water moves too quickly over a landscape. This can cause increased erosion, flooding, and drastic temperature change in waterways. Urban areas are especially susceptible to stormwater runoff because of the large amounts of impervious surface. The infographic below shows how the amount of runoff increases as the amount of impervious surface increases.
Storm drains (like those found along curbs) do not go to wastewater treatment plants. Water entering storm drains flows untreated into streams, rivers, ponds, wetlands, lakes, sounds, bays, and oceans. The diagram below shows the difference between a municipal separate storm sewer system (MS4), which we have in North Carolina, and a combined sewer system (CSS) which are used in other parts of the country.
Stormwater Pollutants
Since stormwater is not treated, it can pick up and carry numerous pollutants into our waterways. Many of these pollutants can cause problems in very small amounts. Polluted stormwater runoff is often considered a non-point source pollutant, meaning that it comes from such varied and widespread sources across the landscape that it is difficult to identify where the pollution starts.
Did you know that sediment is the number-one pollutant in the country and in North Carolina? Sediment comes from anywhere soil is disturbed and is allowed to enter waterways. When it is suspended in the water, it clouds water and suffocates aquatic life. When it settles out of water, it deteriorates habitats for fish and plants by burying stream riffles, which add oxygen to water.
The “Big 6”
Flip through the image carousel to learn more about the “Big 6” common stormwater pollutants and how you can prevent them.
Pet Waste
Yard Waste
Household Hazardous Waste (HHWs)
Vehicle Maintenance
Litter
Pesticides, Herbicides, and Fertilizer
If you are interested in learning more about the different types of water pollution and why protecting our water sources is important, check out the Basement Guides to Water Pollution infographic site.
Stormwater Solutions
Green Stormwater Infrastructure (GSI)
Conventional stormwater systems are designed to move stormwater quickly and efficiently away from where it falls. Green Infrastructure is a way of constructing our built environment that helps mimic natural systems and slow down, soak up and spread out stormwater. Below are a few examples of green stormwater infrastructure that you may have seen in your own city, town or neighborhood.
Green Roofs or eco-roofs are a type of green infrastructure designed to capture and absorb stormwater from buildings. Green roofs also help with building insulation and can provide habitat for pollinators and other animals in urban settings.
Conventional stormwater systems are designed to move stormwater quickly and efficiently away from where it falls. Green Infrastructure is a way of constructing our built environment that helps mimic natural systems and slow down, soak up and spread out stormwater. Below are a few examples of green stormwater infrastructure that you may have seen in your own city, town or neighborhood.
Green Roofs or eco-roofs are a type of green infrastructure designed to capture and absorb stormwater from buildings. Green roofs also help with building insulation and can provide habitat for pollinators and other animals in urban settings.
Pervious pavement, also known as permeable pavement, is a type of pavement with high porosity that can be used on sidewalks, roads, and parking lots to help stormwater infiltrate rather than run off. Examples of pervious pavement substrates include some types of bricks, stones, and gravel.
Rain gardens are gardens built in shallow depressions that help capture, filter and infiltrate stormwater during rain events. When properly installed, standing water in a rain garden will be soaked up in 48 hours or less.
Trees and urban tree canopies can help reduce stormwater runoff by intercepting and soaking up water through their leaves and roots. Trees also help decrease the temperature of stormwater runoff by providing shade and can prevent erosion by stabilizing stream banks with their roots.
A stormwater wetland is a wetland constructed specifically to retain and treat stormwater runoff.
A riparian buffer is a strip of vegetation along a waterbody that helps stabilize the banks, filter water, prevent erosion, provide shade, and protect the waterbody from surrounding land uses. Maintaining and restoring riparian buffers play an important role in controlling water quality throughout a watershed.
A forested/grassed stream buffer in Chatham County (photo credit: Maya Cough-Schulze
To learn more about the stormwater benefits of green infrastructure, you can visit the EPA Green Infrastructure webpage.
Stormwater Regulations
National Pollutant Discharge Elimination System (NPDES)
NPDES Phase I and II stormwater permitting programs were established under the Clean Water Act and delegated to the North Carolina Division of Water Quality (now Division of Water Resources) for implementation. Phase I began in 1990 and applies to NC local governments with populations of more than 100,000. Phase II is an expansion of the NPDES Phase I program and addresses stormwater discharge from communities serving less than 100,000 persons. NPDES communities are required to follow the six minimum control measures (MCM’s): Public Education and Outreach; Public Participation/Involvement; Illicit Discharge Detection and Elimination; Construction Site Runoff Control; Post Construction Runoff Control; and Pollution Prevention/Good Housekeeping.
MS4 Program
MS4 stands for Municipal Separate Storm Sewer System – a subprogram of NPDES, MS4 permits are issued by NC DEQ, and require ‘urbanized’ areas to engage in the following:
- Public Education & Outreach
- Public Involvement & Participation
- Illicit Discharge Detection & Elimination
- Construction Site Runoff Controls
- Post-Construction Site Runoff Controls
- Pollution Prevention & Good Housekeeping for Municipal Operations
- Municipal Facilities Operation and Maintenance
- Spill Response
- MS4 Operation and Maintenance
- Municipal Stormwater Control Measure (SCM) Operation and Maintenance
- Pesticide, Herbicide and Fertilizer Management
- Vehicle and Equipment Maintenance
- Pavement Management
Jordan Lake
The Jordan Lake watershed is a massive regional resource utilized by 10 counties, 27 municipalities, and nearly 700,000 water customers (see Figure below), and is continuing to be more populous every day. As challenges with water quality and water supply increase with growing populations, the need for water resources dialogue that crosses jurisdictional lines becomes more and more imperative. While many of the rules are met through NPDES Phase II requirements, the Jordan Lake Rules require municipalities and Counties in the watershed to adopt additional measures to reduce nutrient inputs to the lake.
