Stormwater Management Program

About Stormwater Management

Stormwater runoff is rain or snowmelt that flows over land and does not percolate into the soil. Stormwater runoff occurs naturally, in small amounts, from almost any type of land surface, especially during larger storm events.

Impervious surfaces, such as buildings, homes, roads, sidewalks, and parking lots, can significantly alter the natural hydrology of the land by increasing the volume, velocity, and temperature of runoff and by decreasing its infiltration capacity. Increasing the volume and velocity of stormwater runoff can cause severe stream bank erosion, flooding, and degrade the biological habitat of these streams. Reducing infiltration can lower ground water levels and affect drinking water supplies.


In addition, as stormwater runoff moves across surfaces, it picks up trash, debris, and pollutants such as sediment, oil and grease, pesticides, and other toxins. In most cases, polluted stormwater runs into storm sewers and ditches or directly into streams, rivers, and lakes without treatment. Polluted stormwater runoff can have many adverse effects on plants, fish, animals, and people.
  • Sediment caused by soil erosion can cloud the water and damage aquatic habitats.
  • Excess nutrients such as phosphorous and nitrogen can promote the overgrowth of algae and deplete oxygen. Fish and other aquatic organisms can't exist in water with low dissolved oxygen levels.
  • Bacteria and other pathogens carried into lakes and rivers can contaminate drinking water supplies and beaches, making drinking water advisories, and beach closures necessary.
  • Debris – plastic bags, six-pack rings, and cigarette butts – washed into bodies of water can choke, suffocate, entangle, or disable aquatic life like ducks, fish, turtles, and birds.
  • Household hazardous wastes like pesticides, paint, solvents, used motor oil, and other auto fluids can poison aquatic life.
Municipal Separate Storm Sewer System MapOutfallMap_2016
       Click Image Above to See Ontario County's MS4 Boundary Map (Updated 3/2016)

Portions of Ontario County have been designated by the U.S. Environmental Protection Agency as a small Municipal Separate Storm Sewer System (MS4) that requires the preparation and implementation of a Stormwater Management Plan.

In accordance with the EPA Stormwater Phase II Final Rule, the Ontario County Department of Public Works is developing a Stormwater Management Plan aimed at reducing the amount of pollutants discharged into receiving waters from its storm sewer system to the maximum extent practicable.

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Comments on the 2016-2017 Ontario County MS4 Annual Report or request a public meeting to ask questions and make comments.

Ontario County MS4 Annual Reports
2016-2017 Ontario County MS4 Annual Report | View Archived Reports