Stormwater Management: Downey vs South San Gabriel
How do stormwater management rules compare between Downey, CA and South San Gabriel, CA?
Downey and South San Gabriel have similar restriction levels.
Downey, CA
Los Angeles County
Downey is subject to LA County MS4 NPDES permit requirements for stormwater management. New development and significant redevelopment must implement Best Management Practices (BMPs) for stormwater quality.
View full Downey rules →South San Gabriel, CA
Los Angeles County
Unincorporated LA County falls under the LA County MS4 NPDES permit. The LACFCD operates one of the largest flood protection systems in the world, including 14 dams and 80,000+ catch basins. Low Impact Development standards apply to new construction. The district captures and infiltrates 270,000+ acre-feet annually.
View full South San Gabriel rules →Key Facts Comparison
| Fact | Downey | South San Gabriel |
|---|---|---|
| Permit | LA County MS4 NPDES | - |
| New Development | BMPs required | - |
| Reporting | Illicit discharge reporting to city | - |
| Enforcement | Public Works Department | - |
| MS4 Permit | - | LA County NPDES |
| LID Required | - | For new development |
| LACFCD | - | 14 dams, 80,000+ catch basins |
| Annual Capture | - | 270,000+ acre-feet infiltrated |
Highlighted rows indicate differences between cities.
Downey FAQ
Do I need a stormwater plan for my project?
Generally required for new construction and major renovations that increase impervious surface area. Small residential projects may be exempt.
What is an illicit discharge?
Any non-stormwater substance entering the storm drain system, including paint, oil, chemicals, or sediment. Report violations to Downey public works.
South San Gabriel FAQ
What can go into storm drains in LA County?
Only stormwater. Illicit discharge of chemicals, wash water, paint, oil, or other pollutants is prohibited under Title 12 and the MS4 permit. Storm drains flow directly to rivers, ocean, and groundwater.
What are LID standards?
Low Impact Development standards require new development to capture and treat stormwater on-site through features like bioswales, permeable paving, cisterns, or rain gardens. They apply to new construction and major renovations.
How do I report illegal dumping into storm drains?
Call the LA County illegal dumping hotline at (888) 846-0800. For active spills or hazardous discharges, call 911 or the LA County Fire Department hazmat line.
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