Stormwater Pollution Facts

  • 126 rivers and lakes in Vermont are so polluted, meaning that they do not meet basic minimum water quality standards, that they are considered “impaired” by definition. Vermonter’s cannot swim or expect to catch fish in many of them.
  • 26 stream are principally impaired by stormwater runoff from urban and suburban areas
  • 73% of stormwater impaired streams, 19 total, drain directly or indirectly to Lake Champlain; 12 are located in Chittenden County.
  • Causes of impairment include sediment, nutrients such as phosphorous and nitrogen, toxics, thermal pollution, stream modification, and pathogens, which cause disease in humans.
  • Phosphorous pollution in Shelburne Bay and the Main Lake is primarily due to stormwater runoff from urban and suburban development; Phosphorous impairment in the Otter Creek section is at least 50% due to stormwater pollution.
  • Sediment is one of the principal cause of impairment due to stormwater:
    • Acts as a transport for other pollutants such as phosphorous;
    • Causes an inability for receiving waters to support aquatic life;
    • Flows directly from developed land and unstable stream banks caused by development.
  • Stream bank instability results from concentrated, high volume flows defined as “flashy.”
    • Unnatural volume of water in a short period of time;
    • Less ground water recharge which means that aquifers are not recharged and flows are not maintained during dry spells;
    • Both factors are a function of impervious surface in the watershed.
  • Even under the new 2002 standards, a less than perfect 80-90% reduction in sediment equates only to a 40-60% removal for phosphorous.