Stormwater, or non-point source pollution, is the leading cause of water pollution in the United States today. Stormwater pollution results from rainfall or snowmelt contacting and carrying contaminants over and through the ground, eventually entering lakes, rivers, wetlands, coastal waters and even underground drinking water sources.

Examples of non-point source pollutants include:

  • Fertilizers, herbicides and insecticides from residential areas and agricultural lands

  • Oil, grease and toxic chemicals from urban runoff and energy production

  • Sediment from improperly managed construction sites, crop and forest lands and eroding streambanks

  • Salt and de-icing agents from roads

  • Bacteria and nutrients from pet waste, wildlife, damaged sewer lines and faulty septic system

Courtesy US Environmental Protection Agency

Courtesy US Environmental Protection Agency



Stormwater runoff is directly related to the amount of impervious surface cover, such as streets, parking lots and rooftops, where water is unable to be absorbed. Improperly managed stormwater washes pollutants into our streams and rivers. As with many urban watersheds, the Mystic is greatly impacted by stormwater.

The effects of stormwater reach farther than just polluting the waters. As the many residents in the Mystic River watershed have seen, stormwater can cause flooding, habitat degradation, sewage backups and erosion. The problems related to stormwater runoff are not going to go away, and will only increase. As more and more open space land is developed and covered by impervious surfaces, stormwater cannot infiltrate into the ground and is forced to become runoff.

All operators of stormwater drainage systems, such as municipalities and public agencies, are required to have stormwater discharge permits.  These permits are administered by the Environmental Protection Agency (EPA) and the Massachusetts Department of Environmental Protection (DEP).

The Mystic River Watershed Association advocates for Low Impact Development (LID), or development that limits the amount of stormwater runoff through designs including green roofs, permeable pavement, bioretention facilities and rain gardens. 


  • Do not use or limit the use of fertilizers, herbicides and insecticides in your lawn and garden.

  • Always pick up after your pet.

  • Properly dispose of all toxic materials; NEVER use storm drains.

  • Use non-toxic products whenever possible.

  • Take your car to the car wash instead of washing it in the driveway.

  • Check car for leaks and recycle motor oil.

  • Plant native trees and vegetation along river banks and in your yard.




If you see evidence of non-point source pollution, such as dumping in storm drains, clogged storm drains, uncovered construction sites, leaking gas or oil barrels, hazardous waste, illegal trash dumping, dry weather discharge in stormwater pipes, illegal connections to stormwater systems, or anything else that you think might be a problem, contact your local stormwater citizen tip line, Department of Public Works (DPW), or the Mystic River Watershed Association (781-316-3438 or


Point Source Pollution is a type of pollution that can be definitively identified as originating from a single source. Examples of point source pollutants are output from a sewage treatment plant and fuel waste discharged from a speedboat.