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 from almost any type of land surface, especially during larger storm events.

Impervious surfaces such as roads, sidewalks, parking lots and roofs 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 capacity of the land can lower ground water levels and affect drinking water supplies.

Please click here for a helpful glossary of terms pertaining to the water cycle!  

Stormwater Pollution

As stormwater runoff moves across surfaces, it picks up trash, debris, and pollutants such as nutrients, 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 harmful algae blooms, depleting the dissolved oxygen in waterbodies that fish and other aquatic life need to survive.
  • 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.


MS4 stands for Municipal Separate Storm Sewer System

The New York State MS4 General Permit authorizes stormwater discharges from municipally owned storm sewer systems (MS4s) to streams, lakes and other waters of the State

The permit requires MS4s to develop and implement a Stormwater Management Program (SWMP) consisting of Six Minimum Control Measures designed to reduce the discharge of pollutants from the MS4 to the maximum extent practicable

The SWMP is only required to be implemented within the Urbanized Area as defined by the US Census Bureau 

Municipal Separate Storm Sewer System Map

MS4 & Outfall Map (Updated 12/2017)
       Click Image Above to See Ontario County's MS4 Boundary Map (Updated 12/2017)

  * Email
Use this e-mail link (above) to send us your comments on the 2018-2019 Ontario County MS4 Annual Report or request a public meeting to ask questions and make comments.

Ontario County MS4 Annual Reports
2019-2020 Ontario County MS4 Annual Report | View Archived Reports