Westchester County
Individual city/town/village building departments / Westchester County Soil & Water Conservation District
CountyMS4 Phase IVerified 2026-03
Local Permit / Authorization
- Permit Required
- Yes
- Permit Name
- Municipal Building Permit with Stormwater Management / County Soil & Water Review
- Submit To
- Individual city/town/village building departments / Westchester County Soil & Water Conservation District
- Lead Time
- Municipal permit review 2–6 weeks; county review concurrent for projects in county drainage or watershed areas
- Application Method
- Building permits via individual municipality; county-level reviews for projects impacting county drainage infrastructure or NYC watershed
- Fee
- Municipal permit fees per project scope; county review fees may apply
Water Quality Standards
- Impervious Cover Limit
- No countywide cap; post-construction management per NYSDEC MS4 permit; NYC East of Hudson watershed areas have stricter thresholds
- On-Site Treatment Required
- Yes
- Detention Required
- Yes
- Detention Standard
- Manage the first 1 inch of rainfall on-site per NYS Stormwater Management Design Manual; watershed-specific requirements may impose stricter controls
- Turbidity Standard
- Must comply with NYSDEC SPDES CGP; Long Island Sound TMDL for nitrogen applies to northern watershed
Local SWPPP / Drainage Plan
- Local Plan Required
- Yes
- Plan Name
- SWPPP per NYSDEC; local stormwater management plans per municipal ordinances
- PE Stamp Required
- Yes
Plans must be prepared by a NY-licensed PE. Many Westchester municipalities have adopted their own local stormwater ordinances that supplement NYSDEC requirements. NYC East of Hudson watershed areas trigger NYC DEP review.
Local Inspection Requirements
- Requirements
- Municipal inspections at permit milestones. NYC DEP conducts watershed inspections in East of Hudson areas. Post-construction BMPs require maintenance agreements.
- Inspector Qualification
- NYSDEC-approved QI/TC per SPDES CGP; no additional county certification
Special Overlay Zones
NYC East of Hudson Watershed
Trigger: Properties in municipalities within NYC's Croton/East of Hudson drinking water watershed (roughly northern and eastern Westchester)
Restriction: Most stringent: ≥ 5,000 sq ft disturbance threshold; NYC Watershed Regulations apply; impervious surface limits; stormwater management per NYC DEP rules; NYC DEP review and approval required
Long Island Sound Watershed
Trigger: Properties draining to Long Island Sound (southern Westchester)
Restriction: Nitrogen TMDL compliance; enhanced nutrient controls; NYS Long Island Sound Study protections
Hudson River Watershed
Trigger: Properties draining to the Hudson River (western Westchester)
Restriction: Hudson River Estuary Program protections; NYS Coastal Management Program; enhanced water quality BMPs
Design Manual
- Manual Name
- NYS Stormwater Management Design Manual / NYC Watershed Regulations (for applicable areas)
Official Resources
Jurisdiction Notes
Westchester County's stormwater requirements vary significantly by location. Properties in the NYC East of Hudson watershed face the most stringent requirements in the state, with a 5,000 sq ft disturbance threshold and NYC DEP oversight. The county is split between three major watersheds (NYC/Croton, Long Island Sound, and Hudson River), each with distinct water quality drivers. The county's Soil & Water Conservation District provides technical assistance.
Remember: These local requirements are in addition to the NYSDEC state construction permit. Both must be satisfied before breaking ground.
Disclaimer: This information is provided for general reference only. Always verify requirements directly with Individual city/town/village building departments / Westchester County Soil & Water Conservation District and the agency website before beginning construction.