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Municipal Separate Storm Sewer System


The New York City Department of Environmental Protection East of Hudson (NYCDEP EOH) Watershed is a Municipal Separate Storm Sewer System (MS4) regulated by the New York State Department of Environmental Conservation (NYSDEC). As a regulated MS4, the NYCDEP EOH is required to comply with its Phase II Storm Water Management Plan.

MS4 Annual Report

The Draft 2017-2018 MS4 Annual Report

The 2016-2017 MS4 Annual Report

The 2015-2016 MS4 Annual Report

MS4 Interim Report

The 2017 MS4 Interim Report is now available online.

The 2016 MS4 Interim Report

MS4 Notice of Intent

The MS4 Notice of Intent is now available online.

Programs and Practice Measures

The Phase II Stormwater regulations require NYCDEP EOH to implement programs and practices to control stormwater runoff that may be polluted. These have six minimum measures:

  1. Public education and outreach
  2. Public involvement and participation
  3. Illicit discharge detection and elimination
  4. Construction site stormwater runoff control
  5. Post construction stormwater management practices
  6. Pollution prevention and good housekeeping

Stormwater from a rain event or melting snow can pick up and move sediment and a variety of pollutants. Because the stormwater transports whatever is left on our lawns and roads, individual actions make a difference in determining the kinds and amounts of pollution.

In the EOH Watershed, the main pollutant of concern is phosphorus.

You can also learn more about pollution prevention practices by visiting the NYSDEC website at

The NYCDEP EOH has established a stormwater hotline so that any illegal dumping or discharges to any storm sewers can be reported by calling (914) 232-8642 and (845) 334-7185, or by email

Understanding the Phosphorous Issue

Understanding the Phosphorous Issue
Introduction of phosphorous into freshwater systems often leads to eutrophication, which is a condition where high nutrient levels lead to excessive production of algae and macrophytes in aquatic systems.
Learn more
An Informative Guide on Phosphorus


Stormwater in the Watershed
Stormwater is generated by rain or snow that runs off a land surface such as saturated soils or impervious (non-porous) surfaces like roof tops and parking lots. Many contaminants can be found in stormwater including sediment, metals, oils, nutrients, bacteria and viruses.
Learn more

Stormwater Management Programs

Stormwater Management Programs in the Watershed
Given that New York City’s Watershed Regulations require strict management of stormwater, DEP works with local partners to implement a variety of stormwater management programs that assist businesses and communities with meeting enhanced regulatory requirements.
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Reservoir Levels

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Normal: %