Environmental Rules in Westchester County, NY (2026)

2 county-level rules, plus city-specific rules for 4 cities in Westchester County, New York.

Verified from official government sources

Note: These county rules apply to unincorporated areas of Westchester County. If you live within an incorporated city, that city's own rules apply: see the city list below.

Stormwater Management

Westchester County bans any non-stormwater discharge into its municipal separate storm sewer system countywide, with narrow exemptions for things like pool backwash and residential car-washing runoff.

Westchester County MS4 Stormwater Discharge Ban

Heavy Restrictions

Laws of Westchester County § 823.05(1)

No person shall discharge or cause to be discharged into the County's MS4 any materials other than stormwater. The commencement, conduct or continuance of any illicit discharge to the MS4 is prohibited, except as described in subsection 2 of this section. A discharge can be direct through a pipe, or indirect via overland surface flow.

Full ordinance details →Official source ↗

Erosion Control

Westchester County requires anyone holding an industrial or construction SPDES stormwater permit that discharges into its MS4 to fully comply with that permit and prove it to the Commissioner.

Westchester County Construction Stormwater Permit Rule

Some Restrictions

Laws of Westchester County § 823.10

Any person subject to an industrial or construction activity SPDES stormwater discharge permit where such discharge enters the County's MS4 shall comply with all provisions of such permit. Proof of compliance with said permit may be required in a form acceptable to the Commissioner prior to the allowing of discharges to the County's MS4.

Full ordinance details →Official source ↗

Environmental Rules by City in Westchester County

4 cities in Westchester County have their own environmental rules rules. Each link goes to that city's dedicated page with code citations.

YonkersPop. 211,569

7 verified rules • Boat Dock Permits, Coastal Development

New RochellePop. 79,726

5 verified rules • Boat Dock Permits, Flood Elevation Requirements

Mount VernonPop. 73,893

4 verified rules • Boat Dock Permits, Erosion Control

White PlainsPop. 59,599

2 verified rules • Coastal Development, Stormwater Management

All Westchester County ordinances

See every category we cover for Westchester County: parking, noise, fences, fires, animals, pools, and more.

Westchester County Ordinance Hub →