Stormwater Management: Altadena vs Downey
How do stormwater management rules compare between Altadena, CA and Downey, CA?
Altadena and Downey have similar restriction levels.
Altadena, CA
Los Angeles County
LA County operates under a regional MS4 permit issued by the LA Regional Water Quality Control Board. LA County Code Title 12 prohibits discharging non-stormwater (sediment, chemicals, paint, sewage, washwater) into storm drains.
View full Altadena rules →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 →Key Facts Comparison
| Fact | Altadena | Downey |
|---|---|---|
| Authority | LA County Code Title 12 + State Water Board MS4 | - |
| Construction SWPPP | Required ≥1 acre disturbance | - |
| Illicit Discharge Hotline | (888) CLEAN-LA | - |
| Permit | - | LA County MS4 NPDES |
| New Development | - | BMPs required |
| Reporting | - | Illicit discharge reporting to city |
| Enforcement | - | Public Works Department |
Highlighted rows indicate differences between cities.
Altadena FAQ
Can I hose my driveway into the gutter in Altadena?
Generally no — soapy or sediment-laden runoff into the storm drain violates the LA County NPDES MS4 permit and Title 12.
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.
Compare other topics
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