The MS4 Construction Permit program has now been superseded by the Stormwater Permitting Program. In 2022, the City amended Chapter 31 and Chapter 19 of the Administrative Code changing requirements for how stormwater is managed on all new and redevelopment sites that discharge to City sewers.
The Stormwater Permitting Program:
- Aligns the RCNY Chapter 31 stormwater quantity and flow rate requirements with the RCNY Chapter 19.1 Construction/Post-Construction permitting program water quality requirements.
- Extends DEP’s permitting, inspection and enforcement program for development projects from only municipal separate storm sewer system (MS4) areas to combined sewer system (CSS) areas, including requirements, standards and penalties for construction and post-construction stormwater controls.
- Updates sewer connection volume requirements and maximum stormwater release rates for both CSS and MS4 areas.
- Lowers DEP’s current lot size threshold for the construction/post-construction stormwater permitting program from one-acre (43,560 square feet) to 20,000 square feet (sf) and adding the creation of 5,000 sf of impervious area as an additional trigger.
- Encourages development projects greater than or equal to 20,000 sf to use green infrastructure to meet requirements of both Chapter 31 and 19.1.
- Allows greater flexibility in stormwater management design options, while simplifying the rules and making them consistent across the city, regardless of the borough.
- References the new NYC Stormwater Manual.
Stormwater Permitting & Tracking System
To apply for Stormwater Permits you must submit an application using our Stormwater Permitting and Tracking System or “SWPTS.”
Once you login to SWPTS, the system will walk you through the various steps of the permitting process. For your application, you will need to have completed your Stormwater Pollution Prevention Plan (SWPPP). Please refer to our SWTPS User Manual, the SWPPP Template, the No Net Increase Calculator, and the Stormwater Maintenance Easement Instructions and Pre-Approved Maintenance Easement Template for additional guidance:
Stormwater Permit Criteria
Any development or redevelopment project (public or private) will require a Stormwater Permit if:
- It drains to a City-owned sewer system
- It disturbs 20,000 sf or more of soil, or adds 5,000sf or more of new impervious area
When a permit applies, prepare a stormwater pollution prevention plan (SWPPP) that meets up to four requirements, as needed:
- Erosion and sedimentation (ESC)—to minimize the discharge of pollutants during construction activities.
- Water quality (WQ)—to manage runoff from small, frequent storm events that can significantly impact the quality of receiving waters in both MS4 and CSS areas.
- Runoff reduction (RR)—to maintain a minimum level of runoff reduction during small storms to preserve natural hydrologic functions.
- No-net increase (NNI)—to reduce pollutants of concern in MS4 sewershed areas that discharge to an impaired waterbody.
Stormwater Permit Resources