Stormwater Basics 101

What is stormwater runoff?



  • Stormwater runoff is rain or melted snow that flows over land.
  • Stormwater infrastructure, such as storm drains and ditches, collect runoff and convey it without treatment directly into waterbodies. Polluted runoff affects drinking water, human health, wildlife, and property values. 

Why are stormwater drainage systems important?



  • Stormwater system infrastructure provides drainage that protects roads and the built environment from failure and flooding.
  • Adequately sized drainage systems are a critical utility for new development and urban expansion.
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Why is our work important?



  • Drainage systems require periodic repair and maintenance to continue to function effectively. 
  • In the face of increasing frequency and intensity of storms, drainage systems will be even more critical to our future economy and growth by alleviating flood risks which cause erosion and property damage. 
  • Municipalities have an important responsibility in managing and reducing the pollution in stormwater drainage systems.

What are common stormwater pollutants?

  • Soil sand, and sediments can cloud the water and smother wildlife habitat
  • Chemicals (fertilizer, weed & bug killers, vehicle fluids, coal tar pavement sealers, etc.) are carried with runoff and can be toxic to wildlife.
  • Pet waste contains bacteria that can wash into swimming areas and create health hazards and may contribute to beach closures. 
  • Salt, which is spread onto paved surfaces to melt snow and ice, dissolves in water or snowmelt. Once salt gets into our water it cannot be removed. Salt in our waterways can be toxic to wildlife.
  • Debris (cigarette butts, household trash, etc.) is unsightly and can harm wildlife. 

Pollutant Types

What does the town do about stormwater?

The Clean Water Act requires municipalities like Windham, which as referred to as "municipal separate storm sewer systems (or MS4s), to comply with permit regulations that were established to minimize the harmful effects of polluted stormwater runoff and improve local water quality. To help accomplish these overall goals, the Town's Stormwater Management Plan identifies specific minimum control measures that must be implemented over ongoing 5 year permit periods.

Photo and Content Credit: CCSWCD, City of South Portland, Think Blue Maine, Town of Kittery