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Mercer County, NJ Environmental Rules: Stormwater Management (2026)

Some Restrictions
Compiled from the official code textEditor Martyn O'NeillLast verified August 2026

Key Facts

Core rule
No diverting runoff onto County drains/roads
Storm drain tie-in
Needs separate RCP/ROWOP
Engineer review time
Up to 2 weeks
Driveway rule
No adverse drainage impact allowed
Penalty
Up to $500 fine, 90 days jail

Summary

Mercer County Code § 5.03.050 bans diverting stormwater, sump-pump discharge or runoff onto County roadways, gutters, drains, bridges or culverts, and bars any construction that lets dirt or silt accumulate in County drainage facilities. New driveways and roads must also avoid impacting County roadway drainage under § 5.03.030(C)(7), and any storm drain connection needs a separate permit.

These county ordinances apply to unincorporated areas of Mercer County. Incorporated cities within the county may have their own rules that take precedence over county-level regulations.

Diverting surface, sump pump and other runoff waters to and upon County roadways, rights-of-way, drains, gutters, bridges, and culverts. ... no person, persons, firm, corporation, or municipality shall do or cause to be done any act including the construction of buildings, private or public roadways, grading, landscaping, or otherwise, which shall cause or result in the accumulation of dirt, silt, earth, foreign objects, or any other materials upon the County roadway or right-of-way, stormwater drainage facilities, gutter, bridge, or culvert. ... The applicant shall ensure that any stormwater runoff as a result of the driveway or new road construction does not adversely impact drainage on the County roadway.

View official code

Full Breakdown

Mercer County treats stormwater interference with its road drainage system as a right-of-way violation, not a general environmental filing. 030(C)(2). ' Because these rules sit in the right-of-way chapter rather than a separate stormwater ordinance, Mercer County enforces them the same way it enforces excavation and encroachment violations, through the County Engineer's permit review and the Sheriff's general penalty authority.

Violations & Fines

A property owner or contractor who diverts runoff onto County roads, blocks a gutter or culvert with fill, or lets construction silt reach County drainage facilities is liable for the County's full cost of clearing the obstruction, and, under § 5.03.060(B)(2), faces a fine of up to $500, up to 90 days in the County jail, or both, enforced by the County Sheriff.

Frequently Asked Questions

Can I redirect my sump pump or downspout to the County road?
No. Section 5.03.050(H) specifically prohibits 'diverting surface, sump pump and other runoff waters to and upon County roadways, rights-of-way, drains, gutters, bridges, and culverts.' Redirecting drainage that way is treated the same as physically obstructing the County right-of-way and carries the same penalty.
Do I need a permit just to connect my drain into the County storm sewer?
Yes. Section 5.03.030(B)(2) requires a Roadway Construction Permit/Right-of-Way Occupancy Permit for any connection into the County storm drain system, whether through a new manhole or inlet or tied into an existing one, and the County Engineer has up to two weeks to review it.
What if grading for my new driveway sends extra water onto the County road?
Section 5.03.030(C)(7) requires the applicant to ensure driveway or road construction runoff 'does not adversely impact drainage on the County roadway,' and § 5.03.050(I) separately bans letting construction silt or dirt accumulate in County drainage facilities. Both are enforceable as right-of-way violations.

Sources & Official References

Other rules in Mercer County

Parking Rules: Street Parking LimitsSignificant RestrictionsAnimal Ordinances: Dog Leash LawsSome RestrictionsFire Regulations: Fire Pits & Backyard FiresSome RestrictionsErosion ControlSignificant RestrictionsNoise Ordinances: Amplified Music & Outdoor SoundSignificant RestrictionsParking Rules: Loading ZonesSome RestrictionsParking Rules: EV ChargingSome Restrictions

All Mercer County rules

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