Industrial Stormwater Pollution in MS4 Areas

It is illegal to discharge polluted stormwater to surface waterbodies. Many industrial business owners overlook their site’s potential to pollute surface waters because their stormwater drains to a municipal separate storm sewer system (MS4). Unlike combined storm and sanitary sewers, MS4’s discharge untreated stormwater to surface waters.

If you are an industrial facility in NYC, you should be aware that the Department of Environmental Protection (DEP) is beginning to crack down on the stormwater run-off regulations. There have been an increasing number of MS4 violations issued in areas including but not limited to Jamaica, Staten Island, and Brooklyn along the coast. Click here to see NYC’s map of MS4 areas. In the NYC area, stormwater violations are often accompanied by a lawsuit from an environmental advocacy group.

Is your Industrial Facility polluting stormwater in MS4 areas?

You are connected to a combined-sewer system

If all of the stormwater runoff from your industrial facility discharges to a combined sewer system, then your facility is exempt from complying with the MS4 regulations.

You are NOT connected to a combined-sewer system

If stormwater runoff from your industrial facility does not discharge to a combined sewer system, there are three different options for your facility to comply with the MS4 regulations.

  1. No-Discharge Certificate – This means that no stormwater leaves your facility.
    Often times, this certificate is achieved if your facility has an underground detention system for all of the stormwater, or an on-site pond/leaching basin that collects all of the stormwater.
  2. No-Exposure Certificate – This means that all of the stormwater entering your site discharges without making contact with industrial operations which can cause pollution. This is commonly seen if all industrial work on your site in conducted indoors or under a covered building.
  3. Multi-Sector General Permit – Commonly referred to as the MSGP. You are required to receive a MSGP if stormwater leaves your facility, and could become contaminated on-site from the outdoor industrial activities. This permit involves quarterly inspections and sampling to ensure the water leaving your facility is not contaminating nearby surface water bodies or the storm sewer system. The MSGP involves the following:
    1. NOI – Notice of Intent – This is a form you fill out stating that you intend to follow the regulations involving an MSGP, and would like to receive an MSGP.
    2. SWPPP – Stormwater Pollution Prevention Plan – This is the plan that demonstrates your facility’s strategy to ensure the stormwater entering your site will be protected from pollution. It involves best management practices and a schedule of maintenance.



If you received a Notice of Violation, or a lawsuit from the “River/Bay Keeper”, please give Walden a call, and our stormwater experts can help you comply with the MS4 regulations!

Long Island/ NYC – (516) 624-7200
Capital District – (518) 698-3012
Hudson Valley – (845) 253-8025