Stormwater Management: Altadena vs Topanga
How do stormwater management rules compare between Altadena, CA and Topanga, CA?
Altadena and Topanga 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 →Topanga, 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 Topanga rules →Key Facts Comparison
| Fact | Altadena | Topanga |
|---|---|---|
| Authority | LA County Code Title 12 + State Water Board MS4 | - |
| Construction SWPPP | Required ≥1 acre disturbance | - |
| Illicit Discharge Hotline | (888) CLEAN-LA | - |
| 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.
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.
Topanga 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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