Modesto, CA Environmental Rules: Stormwater Management (2026)
Key Facts
- Governing NPDES permit
- Permit No. CAS083526
- Civil penalty ceiling
- $25,000 per violation per day
- Misdemeanor penalty
- Up to $1,000 fine / 6 months jail
- First infraction fine
- Up to $250
- Enforcing official
- Public Works Director
- Pool/spa discharge
- Banned to MS4; sanitary sewer allowed
Summary
Modesto's Storm Water Management and Discharge Controls Ordinance bans any non-storm-water discharge into the City's municipal storm drain system unless an NPDES permit or listed exception applies, and specifically prohibits roof drains emptying onto sidewalks and pool or spa water entering storm drains. Violators face civil penalties up to $25,000 per day and misdemeanor prosecution.
(a)Illicit Discharge. Any illicit discharge to the City's MS4 is prohibited unless excepted by Section 5-10.202. All discharges to the City's MS4 of material other than storm water must be in compliance with an NPDES permit issued for the discharge or other regulatory requirement issued pursuant to the Porter-Cologne Water Quality Control Act if an NPDES permit is not required or applicable.(d)Roof Run-off. Domestic roof drain leaders may not drain directly to sidewalks and gutters. Any practical method must be administered to discharge roof run-off into permeable areas.(f)Swimming Pool Water. Discharge of water from a swimming pool, hot tub or spa into the City's MS4 is prohibited.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Code of Ordinances: Supplement 71).
Full Breakdown
Title 5, Chapter 10, Article 2 of the Modesto Municipal Code implements the federal Clean Water Act and California's Porter-Cologne Act through NPDES Permit No. CAS083526. 202(d)). 202 exempts routine flows such as landscape irrigation, air conditioning condensate, non-commercial vehicle washing, and uncontaminated groundwater, unless the City or Regional Water Board flags a category as a significant pollutant source. 203. The Public Works Director enforces the chapter with tiered tools under Article 5: verbal warnings for housekeeping lapses, notices of violation for first-time small spills, cease-and-desist orders for major or ongoing discharges, and referral to the Stanislaus County Department of Environmental Resources, the Central Valley Regional Water Quality Control Board, or the City Attorney for willful violations. Any person served with an administrative citation or cease-and-desist order may appeal under Article 5 of Title 1, Chapter 6.
Violations & Fines
Anyone who violates the chapter or causes prohibited pollution is civilly liable to the City for up to $25,000 per violation per day under Section 5-10.702, with the City able to petition Stanislaus County Superior Court to collect the penalty and recover excess treatment costs. Section 5-10.703 makes a violation a misdemeanor punishable by up to $1,000 and six months in county jail, though the City Attorney may instead prosecute it as an infraction: a first infraction conviction draws a fine up to $250, and a second or later conviction within one year draws up to $500. Section 5-10.706 separately declares any violating condition a public nuisance, and the City may recover investigation and attorney's fees under Section 5-10.607 if it prevails in enforcement.
Frequently Asked Questions
Can I drain my swimming pool into the street gutter in Modesto?
What counts as an illicit discharge under Modesto's storm water ordinance?
How much can the City fine a business for a storm water violation?
Who investigates illegal storm drain discharges in Modesto?
Sources & Official References
Other rules in Modesto
California rules heatmap·Compare Modesto to another location·View the California environmental rules overview
See something wrong?
Help us keep this page accurate. If you notice an error or outdated information, let us know.