Rotten-egg smell (hydrogen sulfide)
This is the classic "sewage" smell that isn't sewage. Organic debris — leaves, grass clippings, dead frogs, mulch — sits in a wet sump long enough that anaerobic bacteria start breaking it down and pumping out H₂S. In a South Florida summer, a basin can go from clean to reeking in about six weeks. A vactor pump-out and a rinse of the walls kills it same day. If it comes back within a month, you've got upstream landscaping feeding the sump and you need a hood or a sediment shield.
Sour, dairy-adjacent smell near a restaurant pad
That's FOG — fats, oils, and grease — hitting the stormwater system where it doesn't belong. It means either a grease trap that's overdue for service or, worse, a kitchen doing a mop-bucket dump into a lot drain. We see this constantly at restaurant-heavy centers in Doral, Hialeah, and Fort Lauderdale. The fix is a quarterly cadence, an interceptor if there isn't one, and a hard conversation with the tenant. See our jetting vs vactor guide for how a FOG-lined lateral gets cleared.
Actual sewage smell (rare, but it happens)
A cross-connection between a sanitary lateral and a storm structure — usually from a botched repair a decade ago — will absolutely put sewage in the storm system. This is a regulatory event. In Miami-Dade it's a DERM matter and in Broward it's a health department call. If a dye test in a nearby sanitary cleanout comes out of a storm grate, stop everything and get us out with CCTV. See our DERM NOV playbook.
Petroleum / gasoline smell
Auto shop parcels, gas stations, and older industrial pads where an oil-water separator has failed, been bypassed, or was never sized for actual runoff. A hydrocarbon sheen on standing water in the basin confirms it. This one is the fastest path to enforcement — a sheen visible from the street can be reported by anyone with a phone. Details on the industrial side in our OWS / MSGP guide.
The one-question triage
Ask: does it smell worse right after a storm, or worse during a dry stretch? Post-storm means something washed in from upstream. Dry-stretch means something is sitting and rotting in the sump itself. That single answer tells us which truck to bring.
See catch basin cleaning for what the basic service covers.
