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New York County, NY Environmental Rules: Stormwater Management (2026)

Heavy Restrictions

Verified 1 month ago|Source: NYC DEP Stormwater →

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Key Facts

Primary rule: NYC Unified Stormwater Rule (2022)
Threshold: 20,000 sq ft disturbance or 5,000 sq ft impervious
State permit: NY SPDES administered by DEC
System type: Mostly combined sewer
Federal law

City-specific rules exist: New York has its own stormwater management rules that differ from New York County's county-level regulations. If you live in New York, check the city-specific page instead.

Summary

Manhattan stormwater is managed through NYC DEP combined sewer system rules, the NYC Unified Stormwater Rule, and NY State SPDES MS4 permitting.

Full Breakdown

New York County is served largely by a combined sewer system that carries sanitary sewage and stormwater in the same pipes, leading to Combined Sewer Overflows (CSOs) during heavy rain. NYC Department of Environmental Protection (DEP) administers the Unified Stormwater Rule (effective 2022, updating NYC DEP Chapter 31) requiring stormwater management plans for development and redevelopment sites disturbing 20,000 square feet or more, or creating 5,000 square feet of new impervious area, and for certain connections to the combined sewer. NY State Department of Environmental Conservation (DEC) administers the State Pollutant Discharge Elimination System (SPDES) permit program including MS4 coverage for separately sewered areas. Green infrastructure practices (green roofs, bioswales, rain gardens, permeable pavement) are incentivized and sometimes required. Federal Clean Water Act requirements also apply to construction stormwater.

Frequently Asked Questions

Does my small project need a stormwater plan?

Only if it disturbs 20,000 sq ft or creates 5,000 sq ft of new impervious surface, or otherwise meets Unified Stormwater Rule triggers.

Can I install a green roof?

Yes, and NYC offers a property tax abatement plus stormwater credit for qualifying green roofs and blue roofs.

How does New York County compare?

See how New York County's stormwater management rules stack up against other locations.

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New York County, NY Environmental Rules: Stormwater Management (2026)

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